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What techniques can be used to link environmental conditions to crop yield?

What techniques can be used to link environmental conditions to crop yield?



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Im interested in how we can determine what are the optimal conditions for crops and how deviations from these optimal conditions affect yield. In the literature I have found two main approaches and I was interested if there were more ways that are used or if anyone can think of a more creative way to test the link.

Approach One

Use a greenhouse experiment to isolate all variables bar one and vary it. Measure the change in yield based on that variable.

But this approach is time consuming and it is difficult to include interactions.

Approach Two

Use a model that relies on some base knowledge of that plant - i.e. the base temperature at which growth is zero, and a rough idea of optimal ranges. But requires this base knowledge already.

Potential Approach Three

Use multiple linear regression in combination with field data to create a linear or polynomial model of each variables effect on yield. Interactions can be included easily. But relationships are unlikely to be linear and without prior knowledge it is hard to decide on non-linear models.

Can anyone think of other ways that could be used to test these links?


Photosynthetic hacks can boost crop yield, conserve water

Plants are factories that manufacture yield from light and carbon dioxide -- but parts of this complex process, called photosynthesis, are hindered by a lack of raw materials and machinery. To optimize production, scientists from the University of Essex have resolved two major photosynthetic bottlenecks to boost plant productivity by 27 percent in real-world field conditions, according to a new study published in Nature Plants. This is the third breakthrough for the research project Realizing Increased Photosynthetic Efficiency (RIPE) however, this photosynthetic hack has also been shown to conserve water.

"Like a factory line, plants are only as fast as their slowest machines," said Patricia Lopez-Calcagno, a postdoctoral researcher at Essex, who led this work for the RIPE project. "We have identified some steps that are slower, and what we're doing is enabling these plants to build more machines to speed up these slower steps in photosynthesis."

The RIPE project is an international effort led by the University of Illinois to develop more productive crops by improving photosynthesis -- the natural, sunlight-powered process that all plants use to fix carbon dioxide into sugars that fuel growth, development, and ultimately yield. RIPE is supported by the Bill & Melinda Gates Foundation, the U.S. Foundation for Food and Agriculture Research (FFAR), and the U.K. Government's Department for International Development (DFID).

A factory's productivity decreases when supplies, transportation channels, and reliable machinery are limited. To find out what limits photosynthesis, researchers have modeled each of the 170 steps of this process to identify how plants could manufacture sugars more efficiently.

In this study, the team increased crop growth by 27 percent by resolving two constraints: one in the first part of photosynthesis where plants transform light energy into chemical energy and one in the second part where carbon dioxide is fixed into sugars.

Inside two photosystems, sunlight is captured and turned into chemical energy that can be used for other processes in photosynthesis. A transport protein called plastocyanin moves electrons into the photosystem to fuel this process. But plastocyanin has a high affinity for its acceptor protein in the photosystem so it hangs around, failing to shuttle electrons back and forth efficiently.

The team addressed this first bottleneck by helping plastocyanin share the load with the addition of cytochrome c6 -- a more efficient transport protein that has a similar function in algae. Plastocyanin requires copper and cytochrome requires iron to function. Depending on the availability of these nutrients, algae can choose between these two transport proteins.

At the same time, the team has improved a photosynthetic bottleneck in the Calvin-Benson Cycle -- wherein carbon dioxide is fixed into sugars -- by bulking up the amount of a key enzyme called SBPase, borrowing the additional cellular machinery from another plant species and cyanobacteria.

By adding "cellular forklifts" to shuttle electrons into the photosystems and "cellular machinery" for the Calvin Cycle, the team also improved the crop's water-use efficiency, or the ratio of biomass produced to water lost by the plant.

"In our field trials, we discovered that these plants are using less water to make more biomass," said principal investigator Christine Raines, a professor in the School of Life Sciences at Essex where she also serves as the Pro-Vice-Chancellor for Research. "The mechanism responsible for this additional improvement is not yet clear, but we are continuing to explore this to help us understand why and how this works."

These two improvements, when combined, have been shown to increase crop productivity by 52 percent in the greenhouse. More importantly, this study showed up to a 27 percent increase in crop growth in field trials, which is the true test of any crop improvement -- demonstrating that these photosynthetic hacks can boost crop production in real-world growing conditions.

"This study provides the exciting opportunity to potentially combine three confirmed and independent methods of achieving 20 percent increases in crop productivity," said RIPE Director Stephen Long, Ikenberry Endowed University Chair of Crop Sciences and Plant Biology at the Carl R. Woese Institute for Genomic Biology at Illinois. "Our modeling suggests that stacking this breakthrough with two previous discoveries from the RIPE project could result in additive yield gains totaling as much as 50 to 60 percent in food crops."

RIPE's first discovery, published in Science, helped plants adapt to changing light conditions to increase yields by as much as 20 percent. The project's second breakthrough, also published in Science, created a shortcut in how plants deal with a glitch in photosynthesis to boost productivity by 20 to 40 percent.

Next, the team plans to translate these discoveries from tobacco -- a model crop used in this study as a test-bed for genetic improvements because it is easy to engineer, grow, and test -- to staple food crops such as cassava, cowpea, maize, soybean and rice that are needed to feed our growing population this century. The RIPE project and its sponsors are committed to ensuring Global Access and making the project's technologies available to the farmers who need them the most.


Materials and Methods

Two crop simulation models, DSSAT-NWheat (15) and SIMPLE (16), were tested with detailed data from an indoor wheat experiment reported by Monje and Bugbee (13). The wheat crop in this experiment was grown under 20 h/d of light at an intensity of 1,400 μmol/m 2 /s and an atmospheric CO2 concentration of 330 ppm. The two crop models were used to simulate growth and yield under no water or nutrient limitations with 1,800, 1,900, and 2,000 μmol/m 2 /s for 24 h/d and with ±10% radiation use efficiency (RUE) to create a model ensemble. The theoretical highest harvest index for wheat, confirmed to be 0.64 in field observations (23, 24), was then applied to the simulated total biomass to estimate the possible maximum wheat grain yield under controlled indoor conditions. The mean of the simulation ensemble with model uncertainty, expressed as ± the mean of the 10th and 90th percentiles, is presented.

Building and operation costs and cost/return ratios were calculated for a 1-ha, 10-layer indoor vertical wheat production facility, expandable to 100 layers. Details are provided in SI Appendix.


Materials and methods

In a workshop on “Methods for analyzing yield stability in long-term field experiments” at the University of Bonn in 2019, nine topics were identified that are of particular relevance for analysing yield stability in LTEs and other long-term data sets. These topics are the basis for the methodological guidelines (Sect. 3). Examples are used to illustrate each topic.

The examples pertain to data sets from LTEs and other long-term variety trial data sets (Table 1), representing different biophysical conditions and cropping systems in a temperate climate. The analyses were performed with the statistical packages R and SAS. Details about the statistical methods employed are explained for each example separately.


II. Analysis

Data collection is the process of gathering and measuring information on variables of interest. FAOSTAT provides access to over 3 million time-series and cross sectional data relating to food and agriculture. The FAO data can be found in csv format (hurrah!) . FAOSTAT contains data for 200 countries and more than 200 primary products and inputs in its core data set. It offers national and international statistics on food and agriculture. The first thing to get is the crops yield for each country.

Now the data looks clean and organized, but dropping some of the columns such as Area Code, Domain, Item Code, etc, that won’t be of any use to the analysis. Also, renaming Value to hg/ha_yield to make it easier to recognize that this is our crops yields production value. The end result is a four columns dataframe that contains: country, item, year and crops yield corresponds to them.

Using describe() function, few things come clear about the dataframe, where it starts at 1961 and ends at 2016, this is all the available data up to date from FAO.

Climatic factors include humidity, sunlight and factors involving the climate. Environmental factors refers to soil conditions. In this model two climate and one environmental factors are selected, rain and temperature. In addition to pesticides that influence plant growth and development.

Rain has a dramatic effect on agriculture, for this project rainfall per year information was gathered from the World Data Bank in addition to average temperature for each country.

The final dataframe for average rainfall includes country, year and average rainfall per year. The dataframe starts from 1985 to 2017, on other hand, the average temperature dataframe includes country, year and average recorded temperature. The temperature dataframe starts at 1743 and ends at 2013. The variation in years will compromise the collected data a bit where having to unite a year range to not include any null values.

Data for pesticides was collected from FAO, it’s noted that it starts in 1990 and ends in 2016. Merging these dataframes together, its expected that the year range will start from 1990 and ends in 2013, that is 23 years worth of data.

Figure above depicts the final dataframe with selected features for the application of model.


Leaf anatomical features contributing to photosynthesis and plant performance

Leaf anatomical features vary substantially among and within plant species, and are closely related to photosynthetic efficiency under different environmental conditions. Leaf anatomy influences photosynthesis by affecting the distribution of light in the mesophyll, CO2 diffusion, leaf temperature and leaf water relations (Evans and Loreto, 2000 Niinemets, 1999). The anatomical differences between C3 and C4 plants, and the associated increase in photosynthetic efficiency in C4 plants, strongly underscores the importance of anatomical features for photosynthesis and yield (Sage and Sage, 2009). The characteristic ‘Kranz anatomy’ of C4 plants – a special developmental architecture in which mesophyll cells are surrounded by specialized bundle sheath cells in leaves – helps to increase photosynthetic efficiency and allow better photoassimilation of atmospheric CO2 (Wang et al., 2014). This is also closely associated with an increase in vein density, which is likely to be due to auxin-related modifications, in C4 plants (McKown and Dengler, 2009). The genetic basis of these developmental differences between C3 and C4 plants is just beginning to be deciphered (Huang et al., 2016). Notably, the SCARECROW (SCR) and SHORTROOT (SHR) genes appear to be important for establishing the specialized bundle sheath and mesophyll cells in C4 leaves. Although the detailed mechanism underlying SCR/SHR-mediated patterning of Kranz anatomy needs further investigation, SCR is likely to restrict the movement of SHR to the cells that will become bundle sheath (Slewinski et al., 2012). A number of other developmental genes have also been associated with this difference (Liu et al., 2013 Wang et al., 2013) and could be targeted to trigger a C3-to-C4 conversion. Indeed, a global consortium based at the International Rice Research Institute (Philippines) aims to convert C3 rice to C4 by manipulating the biochemistry and anatomy of the plant (von Caemmerer et al., 2012 http://c4rice.irri.org/).

Besides converting C3 plants to C4 plants, there are many other potential ways of changing leaf anatomical features to increase photosynthesis. Maintaining uniform light distribution within a leaf could be an important approach for increasing leaf photosynthesis, as light distribution within a leaf is otherwise highly heterogeneous (Johnson et al., 2005). Certain modifications to leaf anatomical features such as bundle-sheath extensions, which are parenchyma or sclerenchyma cells without chloroplasts connecting the epidermis and vascular bundles, can help to provide a more uniform distribution of light through thicker leaves, thereby enhancing photosynthesis (Buckley et al., 2011). However, the quantitative effects of these anatomical changes on photosynthesis need to be evaluated. Leaf thickness also affects photosynthesis levels. For example, a leaf of minimal thickness, containing all necessary photosynthetic machinery, would allow for more efficient absorption and usage of light energy. This minimal leaf thickness will vary from species to species and will also depend upon environmental conditions. The shape and size of mesophyll cells might also be critical factors for light distribution as well as for CO2 diffusion to RuBisCO, a key CO2-fixing enzyme (Sage and Sage, 2009 Tholen et al., 2012). There is potential to increase photosynthetic efficiency by ∼20% by reducing resistance to CO2 diffusion and optimizing the shape and size of mesophyll cells (Tholen et al., 2012 Zhu et al., 2010).

Although much progress has been made in understanding the genetic regulatory mechanisms that control leaf growth, the molecular mechanisms regulating leaf anatomical traits that influence photosynthesis are still largely unknown. To allow the engineering of a specific leaf anatomy that would achieve a more homogeneous internal light distribution, more efficient CO2 delivery and improved water transport capacity, more effort is required to study the genetic mechanisms underlying different leaf structures.


Contents

    (air, nutrient solution, root-zone, leaf) (%RH) (CO2) (intensity, spectrum, duration and intervals)
  • Nutrient concentration (PPM of Nitrogen, Potassium, Phosphorus, etc)
  • Nutrient pH (acidity)
  • Pests

CEA facilities can range from fully 100% environmentally controlled enclosed closed loop systems, to fully automated glasshouses with computer controls for watering, lighting and ventilation, to low-tech solutions such as cloches or plastic film on field grown crops and plastic-covered tunnels. [4]

CEA methods can be used to grow literally any crop, though the reality is a crop has to be economically viable and this will vary considerably due to local market pricing, and resource costs.

Crops can be grown for food, pharmaceutical and nutriceutical applications. It can also be used to grow algae for food or for biofuels.

Using CEA methods increase food safety by removing sources of contamination, and increases the security of supply as it is unaffected by outside environment conditions, and by eliminating seasonality create stable market pricing which is good for farmer and consumer alike.

CEA is used in research so that a specific aspect of production can be isolated while all other variables remain the same. Tinted glass could be compared to plain glass in this way during an investigation into photosynthesis. [5] Another possibility would be an investigation into the use of supplementary lighting for growing lettuce under a hydroponic system. [6]

A February 2011 article in the magazine Science Illustrated states, "In commercial agriculture, CEA can increase efficiency, reduce pests and diseases, and save resources. . Replicating a conventional farm with computers and LED lights is expensive but proves cost-efficient in the long run by producing up to 20 times as much high-end, pesticidee-free produce as a similar-size plot of soil. Fourteen thousand square feet of closely monitored plants produce 15 million seedlings annually at the solar-powered factory. Such factories will be necessary to meet urban China's rising demand for quality fruits and vegetables." [7]

As of 2018, an estimated 40 indoor vertical farms exist in the United States, some of which produce commercially sold produce and others which are not yet selling to consumers. [8] Another source estimates over 100 startups in the space of 2018. [9] In Asia, adoption of indoor agriculture has been driven by consumer demand for quality. [10] The Recirculating Farms Coalition is a US trade organization for hydroponic farmers. [11]

AeroFarms, founded in 2011, raised $40 million in 2017 and reportedly opened the largest indoor farm in the world in Newark, New Jersey in 2015 [12] by 2018 it built its 10th indoor farm. [12]

Plenty, Inc., based out of South San Francisco, raised over $200 million in 2017. [8] [13]

Economics Edit

The economics of indoor farming has been challenging, particularly the price of electricity, and several startups shut down as a result. [14] Advances in LED lighting have been one of the most important advances for improving economic viability. [8] The high financial cost of investing in CEA presents a challenge that can only be overcome through research & development to innovate sustainable practices. The production potential of these farm networks justifies the investment in infrastructural value and contributes towards the 2030 SDGS to combat carbon footprint. [3]

Organic agriculture Edit

In 2017, the US National Organic Standards Board voted to allow hydroponically grown produce to be labeled as certified organic. [11]


SUMMARY POINTS

Improving crop yields at a pace commensurate with growth in food demand will likely require significant reductions in current yield gaps around the world.

Several methods exist to measure crop yield potential and associated yield gaps, each of which has distinct advantages and disadvantages. Estimates of yield potential can often differ by 50% or more, with estimation especially difficult for rainfed conditions.

A wide range of yield gaps are observed around the world, with average yields ranging from roughly 20% to 80% of yield potential.

Many irrigated cropping systems, including maize in the United States, wheat in South Asia and Mexico, and rice in Japan and Korea, have yields at or approaching 80% of yield potential. This implies that yield gains in these regions will be small in the near future, and yields may even decline if yield potential is reduced because of climate change. Many rainfed cropping systems, in contrast, appear to have relatively large yield gaps that could be closed with existing technologies but persist largely for economic reasons.

Raising average yields above 80% of yield potential appears possible but only with technologies that either substantially reduce the uncertainties farmers face in assessing soil and climatic conditions or dynamically respond to changes in these conditions (e.g., sensor-based nutrient and water management). Although these tools are more often discussed because of their ability to reduce costs and environmental impacts, their role in improving future crop yields may be just as important.


What techniques can be used to link environmental conditions to crop yield? - Biology

Tables 1 and 2 below summarise the main crop areas, cropping systems and average yields in the country as well as in the three northern Governorates.

Table 1. Average (14 Years) Area, Production and Yield of various crops in Iraq

Table 2. Area, Production and Average Yield of various crops in three northern Governorates

I. Dry land field crops

Generally speaking, a wide range of field crops is grown in the rain fed areas in Iraq. Main dray land crops include wheat and barley in cereals, sunflower and sesame in oil seeds, chickpea, lentil, and dry broad bean in pulses and sugar beet in industrial crops. In certain dray land areas, some supplementary irrigation is also provided where the rainfall is not secured.

Wheat is the most important staple food crop in Iraq. Barley is mainly used for animal feed. The annual average (14 years) area covered by wheat and barely is about 1.5 million ha each. Production is about 1 million tons each (FAOSTAT Database). Wheat, barley, chickpea, lentil, dry broad bean and sugar beet are grown during winter as rain-fed crops in the northern Governorates of the country where 400 to 1000 millimetres of rainfall is received annually and the region is considered to be secured for the rain-fed crop production. Wheat is also grown in semi-secured area (200 to 400 millimetre of annual rainfall) with supplementary irrigation. Sunflower and sesame are grown during summer season mainly under irrigation. In some high rainfall areas in the northern Governorates, sunflower is also grown as rain-fed crop. Since barley has some drought resistant capacity, barley is generally grown in comparatively dryer areas than wheat.

Current yield levels of crops in Iraq are significantly lower than the international averages. Average wheat yield is about 727 kg/ha where barley is about 624 kg/ha. Due to prolonged war, sanctions, civil strife and drought of 1999 and 2000, Iraq could not improve the productivity potential of its main field crops. The infrastructures for research and extension services and inputs production established prior to the 1990 war were either damaged during the war or deteriorated afterwards due to shortage of funds for maintenance and operation.

In the northern Governorates, wheat, barley, chickpea, lentil and sunflower are the most important dry land field crops. Chickpea has become a popular cash crop among farmers mainly because of the suitability of the area for its production, attractive market price, crop rotation and soil fertility improvement. The total dry land area in the three northern Governorates is estimated at about 656,280 ha (FAO 2001). The yield levels are slightly higher than in the centre and south. The average wheat yield is 839 kg per ha and barley is 690 kg per ha. The introduction of the Food Basket that is mostly supplied by imported grains had depressing impact on domestic wheat prices and resulted in many farmers switching to barley production for feed.

Ii. Irrigated field crops

Rice, maize, cotton and sunflower crops are mainly grown under irrigation during summer season. Rice is second most important staple food crop and the third major cereal crop in Iraq. Rice covers an annual average area of about 110 000 per ha and its production is estimated at about 212 000 tons (FAOSTAT Database). Annual average area for maize is about 73 000 ha and production is about 137 000 tons. The average rice yield is about 2 000 kg per ha whereas maize yield is 1 900 kg per ha (FAOSTAT Database). Maize is comparatively a new crop in Iraq, introduced to supplement poultry feed production. Rice and maize crops are rotated with vegetables, sunflower and cotton. The productivity of rice and maize decreased during the sanctions period mainly due to shortage of inputs such as fertilisers, pesticides and irrigation water, as well as to substantially reduced research and extension services in the country. In the northern governorate of Iraq, sunflower and rice are grown as irrigated field crops.

Generally winter crops are grown during the period of October to May and summer season crops are grown from March to September.

Fruits and vegetables

Tomato, cucumber, watermelon, onion, okra, eggplant, sweet melon, broad green bean, green bean, sweet pepper, squash, lettuce, spinach, Swiss chard, carrot, cabbage and cauliflower are the main vegetables and date palm, citrus, grape, pomegranate, stone fruits (apricot, plum, peach, almond), pear, olive, apples and fig are the main fruit crops grown in Iraq. Iraq is considered to be the largest producer of date palm fruit in the world.

The cultivated area of vegetables is estimated at about 9% (450,000 ha) of the total cultivated area and about 6% (300,000 ha) is covered by permanent fruit trees. Vegetables and fruits provide good supplementary and nutritive food in daily diet and they also fetch attractive price for the producers. Vegetables are grown all year round in Iraq. Similarly fruit trees are grown throughout Iraq as the climate is considered highly suitable for various fruits. Date palm is the most popular fruit in Iraq, which is grown in the central and southern part of the country. The area covered by date palm alone in the 2002 was 150,000 ha and production was about 650,000 tons (FAOSTAT Database).

Deciduous fruits are mostly grown in the central and northern Iraq due to the presence of cold climate. The seasonal fresh fruits are available almost all the year round.

The quality of fruits produced in Iraq is generally low. Improper harvesting techniques and post harvest handling are the most important reasons for the low quality. Significant amount of grape, fig and apricot fruits are dried and consumed in variety of ways in Iraq. Pomegranates are used for juice extraction and the juice is used for cooking and other purposes.

Some potential for increasing vegetable production has been exploited mainly by using imported high yielding varieties, modern irrigation systems and plastic structures. But fruit sector is very much behind its potentials for possible improvement in productivity and production. Droughts of the 1999/2000 and 2000/2001 destroyed many orchards. Variety mixture, lack of pruning and maintenance, pests and diseases and improper harvesting and post harvest handling are some of the major problems of fruit production in Iraq.

The northern Governorates of Iraq are rich in deciduous fruits and vegetable production. The Oil-for-Food programme was instrumental in improving the productivity of vegetables in northern Iraq. The yield levels of major vegetables, especially tomato, have increased significantly during the last few years. This was mainly due to the supply of high yielding varieties and appropriate technical support under the programme.

Soil fertility and crop yields

Over time, the soils of Iraq have considerably deteriorated in both physical and chemical properties. The fertility deterioration was mainly due to constant removal of crop residues (organic matter) to feed animals, absence of crop rotation and fallowing, compaction of soil due to high animal stocking and use of heavy machines and high erosion imposed by monoculture. Other factor for soil fertility deterioration has been the, limited application of fertilisers caused by shortage and high cost. Monoculture was introduced with the introduction of agriculture mechanisation in Iraq. Monoculture farming also increased weed, disease and pest population along with the depletion of soil fertility. The deterioration in soil fertility has resulted in current yield levels of most crops in Iraq of being significantly lower than the international average.

Seeds

The annual average requirement of wheat and barley seeds is about 167,000 tons and 150,000 tons, respectively. Prior to the sanctions Iraq had established state owned three seed companies with nearly 80,000 tons of seed production and processing capacity. But during the sanctions, seed production and processing capacity of these companies has virtually collapsed.

Currently nearly 95% of the seeds of field crops including cereals are planted as farmers' own saved seeds. Lack of good quality seeds continued to be the main constraints to increasing crop production in Iraq. The seeds produced and distributed during the sanction period have been generally poor in quality. Both physical and genetic purity levels have been low.

The seed industry has suffered from lack of timely maintenance of processing plants and staff incentives. Since the agriculture research has also deteriorated, provision of new crop varieties in the seed production stream through research remained virtually non-existent. Some improvement during the last three years has been made in seed testing and quality control activity with UNDP funding and technical assistance of FAO to State Board of Seed Testing and Certification (SBSTC) based in Baghdad. However, variety development, seed multiplication and processing sectors are in dire state that needed urgent and strong improvement programme. The Government of Iraq has, therefore, proposed the introduction of additional five units of seed processing facilities with 80,000 tons capacity for the centre and south of Iraq under the Oil-for-Food Programme (DPX). The plants, however, have not yet arrived in the country.

In the three northern Governorates of Iraq, seven mobile seed cleaners, each with a capacity of one ton per hour, were provided through the Oil-for-Food programme, and made a significant contribution to improve the supply of quality of wheat and barley seeds. During the year 2001, the mobile cleaners cleaned 12,000 tons of seeds for the farmers additional three seed processing plants have also been proposed to cater for the requirements of seed processing in the three northern Governorates. FAO has also initiated informal improved seed production system for wheat in the northern Governorates. The quality of wheat seed in the north has greatly improved.

Seeds for vegetable such as cucumber, tomato, watermelon, onion, sweet pepper, cabbage, cauliflower and melon are traditionally imported. Similarly prior and during the sanctions period, Iraq has been importing certified and hybrid sunflower seeds. During the period of 1999 to 2002 GOI imported 512 tons of tomato, cucumber, watermelon, onion, pepper, eggplant, squash and green bean seeds which fulfilled only 25% of the total need in the centre and south of Iraq (FAO Baghdad Database). A large proportion of vegetable seeds are supplied by the private sector.

The efforts to develop the agricultural and the seed sector should start with the definition of policies in agricultural research/production, in particular for availability of plant genetic resources and their use in plant breeding to obtain crop varieties adapted to the local conditions, the further development of the whole chain of seed production (basic, foundation seeds, etc.) seed processing/field and lab quality control/storage/distribution, responsibilities of the public and the private sectors, including participatory plant breeding in conjunction with NARS and IARS.

An element that could be successfully applied, at least in the first years of the whole seed process to be developed, is the use of the Quality Declared Seeds as proposed by FAO and successfully applied on other similar difficult situations (Afghanistan, Rwanda) or in peaceful conditions (Costa Rica, Zambia).

In conclusion, there is a need to establish a seed system in the country to add value to its local seed related activities including conservation and sustainable use of PGRFA. AGPS is ready to participate in the elaboration and establishment of local seed and PGRFA policies programmes and projects.

Fertiliser supply

Iraq was self sufficient in compound (N.P) and urea (nitrogenous) fertilisers prior to the sanctions. During the sanctions period, due to lacking in appropriate maintenance and availability of spare parts, the production capacity of the existing three fertiliser factories deteriorated markedly reaching virtual collapse. This consequently reduced the production of required fertilisers and led to substantial decline in fertiliser application rates than in turn resulted in significant reduction in soil fertility and crop productivity. Before the sanctions, Iraq had annual capacity of producing 1.2 million tons of compound (N.P) and 1 million tones of urea fertiliser. Some surplus production used to be exported. Current domestic production covers only about 10% of compound phosphate (130 000 m tones) and 40% of nitrogenous (400,000 m tones) fertilisers. During the period of 2000 to 2002, GOI imported 40,000 tons of Di-ammonium phosphate and 17,000 tons of Potassium sulphate through the Oil-for-Food Programme for the centre and south of Iraq (FAO Baghdad database).

According to FAO estimates, the requirement for the three northern Governorates of Iraq is approximately 134,000 tons of NPK fertilisers per annum. FAO records in the north programme shows that between 1997 and 2002 the Oil-for-Food programme imported nearly 83,000 tons of mainly Di-ammonium phosphate fertiliser for the three northern Governorates. This represented around 20% requirements of the region. Informal and private sectors have been filling the gap in the centre, south and northern Governorates of Iraq. Because of the low price of wheat and barley, most farmers can not afford to apply fertiliser as required for optimum crop production unless it is highly subsidised.

Sustainability of farm production and conservation agriculture

Conservation agriculture goes beyond the single farming practices applied for production of a specific crop. It involves the complete agricultural system where production of crops plays an important role. Conservation farming should start with the adoption of simple procedures such as avoiding burning and preserving crop residue on the soil surface, using the right population of plants using appropriate tillage and planting systems. Implementation of these farming procedures will lead to conservation agriculture and will by itself, increase yield and stabilize production with sustainability. Adoption of more complex farming practices, such as crop rotation and no tillage requires a higher standard of agricultural management and takes much longer time to integrate.

Plant protection

In general, plant pests, diseases and weeds impose a serious threat to crop production in Iraq. Population of weeds, insect pests and diseases was increased by the introduction of monoculture farming in the country. Sunn pest and cover smut in wheat and barley, Dubas bug and Borer in date palm, whitefly in citrus and vegetables and mites in fruits and vegetables are the most important pests and diseases that have been causing serious losses in agriculture production in Iraq. Similarly, several broad and narrow leaf weeds in major crops have also been responsible for the low crop yields in Iraq.

Traditionally, Iraq has been relying heavily on agrochemicals for the control of various weeds, pests and diseases. During the years 1998 to 2002, Iraq imported a total of 655 tons of fungicides, 2,573 tons of herbicides, 3,538 tons of insecticides and 117 tons of nematicides for the centre and south of Iraq. This covered 25% of its pesticides needs (FAO Baghdad database). The gap is filled by informal and private sectors.

Pesticides are applied through either ground or aerial spraying. State Board of Plant Protection controls the use and distribution of pesticides. The ultra-low volume (ULV) pesticides are applied mainly to control serious pests like sun-pest, grasshoppers and date palm diseases through either aerial or ground control application procedures solely undertaken by the State Board of Plant Protection. Emulsion concentrates (EC) pesticides, however, are given to the farmers according to their needs. Upon receipt of specific farmers' requests, the plant protection staff determine the type, quantity and application dose required for each individual case.

In the three northern Governorates, from phase I to VIII, of the Distribution Plans of the Oil-for-Food Programme has imported and distributed nearly 2,100 tons of various agrochemicals and 23,544 sprayers and 2,097 hand dusters to over 50,000 farming families of over 4,000 villages at subsidised prices. The Programme has also trained significant number of farmers and local government staff in plant protection techniques.

Integrated plant pest management (IPPM)

Integrated Plant Pest Management (IPPM) is still in an early stage of understanding, development and adoption in Iraq. Since many serious insects have developed resistance to most pesticides, control of such pests has become extremely difficult especially in some crops like cotton and vegetables. Similarly price of pesticides have also become so high that it is becoming impossible for common farmers to be able to afford. This compelled the government and farmers to look for alternatives to pesticides in controlling pests and diseases in crop production in Iraq. Since 2002 the government has initiated the use of IPPM in cotton by introducing biological control of cotton boll worm insect. Those farmers who applied biological method of controlling cotton boll worm were extremely happy by the success they obtained in cotton production this year (FAO's cotton assessment 2003 January). This shows that IPPM has great role to play in the field of plant protection in Iraq. But, as noted above, the absence of basic infrastructure for research and extension is still the main constraint to the advancement and continuity of such important activity in Iraq.

In the three northern Governorates, Integrated Plant Pest Management activity has been initiated since the last two years and a significant progress has been made in the field of sunn pest and grass hopper control in wheat and other crops.

Bee-keeping

Bee-keeping is a traditional activity in Iraq. Bees are important for crop pollination, honey production and improved farmers' income. Prior to the Oil-for-Food Programme due to war, civil strife and the sanctions, beekeeping activity severely deteriorated. The Programme has provided some limited amount of inputs such as modern beehives, beewax, extracting machines and pesticides to revive the beekeeping industry. However, shortages of required inputs, diseases, pests and limited extension and support services were the main constraints to beekeeping in Iraq. The yield levels are generally low (9 kg per hive per annum as against 15-20 kg per hive per annum). Replacement of traditional beehive by improved ones has been taking place. However, many farmers are still using local beehives that produce much less yield than the improved beehives. There is a wide scope for improving the productivity of beekeeping in Iraq. Yield and quality could be improved significantly by replacing the local beehives, reducing the incidence of diseases and pests and providing support in improving the genetic purity of bee breed and honey processing.

Bee-keeping in the northern Governorates has a better potential than in the centre and south of Iraq. In the north, there is plenty of vegetation (natural forests and agriculture) to sustain beekeeping. FAO through the Oil-for-Food Programme in the north has provided similar items as in the centre and south but covering much larger number of beekeepers. Apart from providing the above basic inputs, FAO has also provided training opportunities to substantial number of beekeepers.

Institutions and services

The ministry of Agriculture and the Ministry of Irrigation are the government institutions responsible for agriculture development in Iraq. Several departments under the Ministry of Agriculture are responsible for plant production and protection activities. The main departments include: State Board of Seed Testing and Certification (SBSTC), State Board of Applied Agricultural Research (SBAAR) for research activities, Agricultural Supply Company (ASCO) for inputs procurement and distribution. Iraqi Company and Mesopotamia Company are mainly responsible for seed production and processing, State Board of Plant Protection (SBPP) for plant protection activities. The Ministry of Irrigation and its department called Centre for Soil and Water Resource (CSWR) are responsible for irrigation water supply. The Colleges of Agriculture in Baghdad and Mosul focus mainly on agriculture research and training.

Main constraints to crop production

Shortages of inputs, lack of extension and research service, and absence of crop rotation have led to substantial decrease in crop productivity, degradation of the natural resource base and increased disease and pest infestations. Main inputs that are especially in short supply include quality seeds, fertilisers, machinery and spare parts, pesticides and sprayers, vehicles for movement and transportation facilities. Extremely low salary of the employees in the agriculture sector is also one of the important factors for low agriculture productivity in Iraq.

Capacity of research and extension services

One of the springboards for agricultural improvement is the generation of relevant technological information and its extension to farmers. The capacity in this field has been severely deteriorated for many years mainly due to lack of staff incentives and physical infrastructure.

Limited supplies of good quality seeds, fertilizer and pesticides

Iraq was self sufficient in quality wheat seed and fertilizer production and supply before the sanctions. The capacity of seed production and processing and fertilizer production has severely deteriorated during the last decade. Current production can supply less than 20% of the total need of the country.

Soil salinity and fertility

Nearly 70% of the cultivable land is estimated to suffer from salinity threat. Shortage of fertilizer supply forced farmers to reduce application rates which greatly reduced overall fertility levels of soil. This was further aggravated by introduction of Monoculture tradition following high mechanization of agriculture in Iraq. This practice that caused fast depletion of soil fertility and increased soil erosion. Monoculture farming has led to increased weeds, pests and disease population in the crop fields. During the severe drought of 1999 and 2000, there was a severe shortage of feed and grazing area needed for the animals. This shortage compelled farmers to graze in the crop residues resulting in a significant depletion of organic matter from the field and high erosion of the soil.

Insect pests such as sunn pest in wheat and barley, dubas bug and borer in date palm, whitefly in citrus and vegetables and mites in fruits and vegetables have caused serious damage to agricultural production in Iraq. Similarly, several broad and narrow leaf weeds in major crops have also led to low crop yields. Many diseases cause substantial loss in vegetable and fruit production.

Aged machinery and poor support services

Prior to sanctions, Iraq had about 40,000 tractors and 5,000 harvesters. All of these machineries have crossed normal life and needed urgent replacement. Although some improvements in replacement of aged machinery and provision of spare parts have been made in the last few years, there is still a lot to be done to meet the shortage in machinery and spare parts.

Land holdings, tenure and credit facilities

With an average farm size of less than 10 ha, uncertain tenure and absence of functioning credit system, farmers have limited opportunity to improve agricultural product and income.

Most of the soft fruits and vegetables delivered to the wholesale markets have been damaged by inappropriate handling, packaging and transport. The quality of grains is poor mainly due to admixture of foreign materials and weed seeds.

Market intelligence, pricing mechanisms and physical facilities are not sufficient to motivate farmers to strive for greater profit through increased production or improved quality.

Heavy infestation of weeds in the river banks and silted canals

Due to drought, water levels went down to record low in the 30 year history of Iraq during 1999 and 2000, which increased weed population along river banks and canals.

While the provision of Food Basket has been greatly supporting the food availability and nutritional intake of the Iraqi population, it had a negative impact on Iraqi agriculture. All the items under food basket are imported. Since there is no provision of purchasing local produce for food basket, there is no incentive to farmers to improve or increase crop production.

Natural advantages of Iraqi agriculture

The climate with cool days during winter and dry, warm and sunny days during summer with plenty of irrigation facilities is a favourable condition for growing a variety of high value crops. Seasonal rainfall ranges from 200 to 1000 mm spread over 4-8 months.

Iraq has a considerable area of good textured soils with good water holding capacity (silty clay loams are the most common) which are suitable for wide range of crops production.

Adequate supply of water resources for irrigation

Annual water source of Tigris and Euphrates rivers and their tributaries are estimated to be 44 billion cubic meters for poor years and 77 billion cubic meters for good years. Ground water resource became an important element for agriculture production since Iraq faced two successive severe droughts during 1998/1999 and 1999/2000 seasons. About 8 million hectares of the total area is estimated as irrigable.

A long tradition of agriculture

Farmers have been practicing wide range of crops growing under both dry land and irrigated conditions for centuries.

About 40% of the population reside in the rural area where family size is large and casual labourers can be found cheaply (often for less than US$ 2/day).

High mechanization and ample fuel supply

The farming system is mechanised even at the small farmers' level in Iraq. The range of machinery supply and replacement of the aged ones has increased considerably during the last few years. Since Iraq is a petroleum producing country, the cost of fuel is inexpensive.

A wealth of livestock sub-sector

Iraq has about 18 million heads of sheep and goat (12 C/S and 6 North), 3 million cattle (2.5 C/S and.0.5 North) and 240 million of chicken (213 C/S and 27 North). Sheep and goat and cattle will need 500,000 tons of cereals and 100,000 tons of legume grains for maintenance only. In addition, another 500,000 tons of cereal grains and 100,000 tons of legume grains will be required for poultry feed.

Potential for increasing agricultural production

Self-sufficiency and exports

Yields can be increased potentially by 2-3 times or even more allowing diversification into new crops and possible export of surpluses. Average wheat production of Iraq is about 1 million tones from 1.4 million ha (about.8 tons/ha). The estimated requirements for 27 million people (e.g. 150 kg/head) will be 4.05 million tons. If productivity is increased by 3 times about 80% of the national need for wheat will be met. If another 400,000 ha area is increased for wheat, Iraq can become self sufficient in fulfilment of wheat requirements for its entire population. Current production of barley for animal and poultry feed is sufficient for Iraq. The climate of Iraq is highly suitable for producing most vegetables and fruits for domestic and export markets. Iraq is one of the largest producer and exporter of Date palm.

In risky environment it is advisable to spread the risk by growing more than one crop. Many grain and forage legumes and oil seed crops can grow in Iraq that will benefit other crops by providing nutrients (nitrogen) and minimizing weed, disease and pest spread.

Improved agriculture can produce more jobs specially in providing services to local processing. If the agro-industries are decentralised from the main centres, migration from the villages to cities will also reduce .

The vital role of agriculture program in Iraq is to enhance domestic food production towards improving the dietary needs of Iraqi population. Agriculture production involves many complex and inter-related biological processes that need careful and balanced interventions to achieve set goals in crop production. The following are some interventions suggested for enhancing agriculture development in Iraq.

Introducing a dynamic research system to generate suitable technologies including high yielding crop varieties for the local conditions of Iraq.

Introducing a vibrant extension service to link the research and diffusion of information developed by research.

Establishment of a sound seed industry development programme linked to research and extension service including involvement of private sector.

Improving soil fertility through,

Minimum tillage to reduce loss of moisture, oxidation of organic matter and avoid deep burial of weed seeds.

Restoring soil organic matter through retention of crop residues which will also give added advantage in reduction of soil erosion and improving retention of soil moisture.

Introduction of suitable crop rotation with legumes including forage and pastures to break disease cycle and provide nitrogenous nutrient to crop plants.

Improvement of agronomic practices-adjusting sowing time, optimum use of fertilizers (macro and micro nutrients) based on soil and tissue tests, use of high yielding varieties and improved weed control practice.

Supporting diversification of crop production through the introduction or cultivation of wide range of new crops and varieties of cereal, legume, oilseeds, vegetables, fruits, forage and industrial crops.

Development of sustainable and environmental friendly plant protection system through the introduction of Integrated Plant Pests Management (IPPM) system.

Supporting improvement of infrastructure which includes facilities of research, extension, post-harvest handling and marketing.


Adjusting planter parameters to match field conditions can maximize emergence and yield

Planter performance is a critical component when laying the foundation for a successful crop season. Environmental and soil conditions can significantly impact crop germination and emergence and help or hinder development of an adequate crop stand early in the season. Adjusting specific planter components and settings to match current field conditions can ensure maximized emergence and increase yield in most cases.

The key planter parameters used to maximize crop emergence include uniform and high-stand establishment, consistent seed depth at planting, and accurate seed placement. To identify the best setting for each parameter, Wesley Porter, an Extension Precision Ag and Irrigation Specialist at the University of Georgia, conducted cotton depth and downforce research, in which he tested three downforce settings, three preplant irrigation applications, three seeding depths, and two seed sizes.

Porter found that wetter field conditions and deeper depths reduced emergence on the whole but using a larger seed produced a slight increase in emergence. Additionally, hill-drop planting was found to overcome some inadequate field conditions, and in some cases, plants were able to compensate for the lack of stand establishment. Overall, Porter found that environmental conditions are a critical factor in successful planting and recommends that growers monitor these conditions and adjust planter depth and downforce accordingly.

Porter explains the research in detail in the webcast "Importance of Planter Depth and Downforce in Cotton Production" and offers more advice to cotton growers. This 28-minute presentation is available through the "Focus on Cotton" resource on the Plant Management Network. This resource contains more than 100 webcasts, along with presentations from a number of conferences, on a broad range of aspects of cotton crop management: agronomic practices, diseases, harvest and ginning, insects, irrigation, nematodes, precision agriculture, soil health and crop fertility, and weeds. These webcasts are available to readers open access (without a subscription).

The "Focus on Cotton" homepage also provides access to "Cotton Cultivated," a resource from Cotton Incorporated that helps users quickly find the most current cotton production information available. These and other resources are freely available courtesy of Cotton Incorporated at http://www. plantmanagementnetwork. org/ foco.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.


The Cultivation and Environmental Impact of Mushrooms

The word mushroom may mean different things to different people in different countries. Specialist studies on the value of mushrooms and their products should have a clear definition of the term mushroom. In a broad sense, “Mushroom is a distinctive fruiting body of a macrofungus, which produce spores that can be either epigeous or hypogeous and large enough to be seen with the naked eye and to be picked by hand.” Thus, mushrooms need not be members of the group Basidiomycetes, as commonly associated, nor aerial, nor fleshy, nor edible. This definition is not perfect, but it has been accepted as a workable term to estimate the number of mushrooms on Earth (approximately 16,000 species according to the rules of International Code of Nomenclature). The most cultivated mushrooms are saprophytes and are heterotrophic for carbon compounds. Even though their cells have walls, they are devoid of chlorophyll and cannot perform photosynthesis. They are also devoid of vascular xylem and phloem. Furthermore, their cell walls contain chitin, which also occurs in the exoskeleton of insects and other arthropods. They absorb O2 and release CO2. In fact, they may be functionally more closely related to animal cells than plants. However, they are sufficiently distinct both from plants and animals and belong to a separate group in the Fungi Kingdom. They rise up from lignocellulosic wastes: yet, they become bountiful and nourishing. Mushrooms can greatly benefit environmental conditions. They biosynthesize their own food from agricultural crop residues, which, like solar energy, are readily available otherwise, their byproducts and wastes would cause health hazards. The spent compost/substrate could be used to grow other species of mushrooms, as fodder for livestock, as a soil conditioner and fertilizer, and in environmental bioremediation. The cultivation of mushrooms dates back many centuries Auricularia auricula-judae, Lentinula edodes, and Agaricus bisporus have, for example, been cultivated since 600 ad , 1100 ad , and 1650 ad , respectively. During the last three decades, there has been a dramatic increase in the interest, popularity, and production of mushrooms through farming worldwide. The cultivation methods can involve a relatively simple farming activity, as with Volvariella volvacea and Pleurotus pulmonarius var. stechangii (=P. sajor-caju), or a high-technology industry, as with Agaricus bisporus, Flammulina velutipes, and Hypsizygus marmoreus. In each case, however, continuous production of successful crops requires both practical experience and scientific knowledge.

Mushrooms can be used as food, tonics, medicines, cosmeceuticals, and as natural biocontrol agents in plant protection with insecticidal, fungicidal, bactericidal, herbicidal, nematocidal, and antiphytoviral activities. The multidimensional nature of the global mushroom cultivation industry, its role in addressing critical issues faced by humankind, and its positive contributions are presented. Furthermore, mushrooms can serve as agents for promoting equitable economic growth in society. Since the lignocellulose wastes are available in every corner of the world, they can be properly used in the cultivation of mushrooms, and therefore could pilot a so-called white agricultural revolution in less developed countries and in the world at large. Mushrooms demonstrate a great impact on agriculture and the environment, and they have great potential for generating a great socio-economic impact in human welfare on local, national, and global levels.

Keywords

Subjects

Introduction

Mushroom cultivation is not only a source for nutritious protein-rich food, it can also contribute to the production of effective medicinal products (Chang & Wasser, 2012 Wasser, 2010, 2014). Another significant aspect of mushroom cultivation is to help reduce pollutants in the environment. The bioconversion of lignocellulosic biomass to food and useful products has had a significant impact on national and regional pollution levels and will continue to increase. (Chang, 1984 Chang & Buswell, 2003a Koutrotsios, Mountzouris, Chatzipavlidis, & Zervakis, 2014). Bioremediation uses mushroom mycelia to remove and break down contaminants and will eventually absorb the pollutants (biosorption process), presenting another influential role of mushrooms in the ecosystem (Dai, 2016 Miller, 2013 Stamets, 2005). Cultivated mushrooms have now become popular all over the world. In 2012 , the world’s total edible and medicinal mushrooms production was estimated at over 31 million tons, which was valued at over US$20 billion (Chang & Wasser, 2012). With no adverse legal, ethical, or safety effects, this form of bioconversion technology has not only favorable socioeconomic, nutritional, and health benefits but also raises employment possibilities (increases job opportunity) and has a positive environmental impact (Mshigeni & Chang, 2013).

What Are Mushrooms?

Mushrooms are unique, as described in the following quote:

Without leaves, without buds, without flowers, yet, they form fruit as a food, as a tonic, as a medicine, the entire creation is precious.

Mushrooms are part of fungal biota characterized by wonder. Different people from different countries have different definitions of a mushroom. Because of this, no one can provide an estimation of how many mushrooms species there are on Earth. A broad use of the term mushroom embraces all large fungi, or all fungi with stalks and caps, or all large fleshy fungi. A more restricted use includes just those larger fungi that are edible and/or medicinal in value. The most extreme use of the term mushroom is in reference to just the edible species of genus Agaricus. For example, the mushroom industry in the United Kingdom and other Western countries is dominated nearly 100% by A. bisporus. This could lead to the mistaken idea that this is the only species regarded as mushrooms. Some industries even consider brown mushrooms as exotic. According to mycologists, there are thousands of different species of mushrooms. These specialists classify mushrooms as a group of macro fungi, which have larger, distinctive fruiting bodies (Chang & Miles, 1992). According to the definition given by Chang and Miles (1992), a mushroom is, in a broader sense, “a macrofungus with a distinctive fruiting body. They can be either epigeous (growing above ground) or hypogenous (growing entirely in the soil), and large enough to be seen with the naked eye and to be picked by hand.” Different mushroom species may belong to one of two phylla in the sub-kingdom Dikarya (common fungi) Basidiomycetes and Ascomycetes. This is reflected in a great range of physical characteristics, including relative edibility. This definition is not a perfect one but can be accepted as a framework (Hawksworth, 2001) for estimating the number of mushrooms on Earth. The most common type of mushroom is umbrella-shaped, with a pileus (cap) and a stipe (stem), such as Lentinula edodes (Figure 1). Other species additionally have a volva (cup), Volvariella volvacea (Figure 2), or only an annulus (ring), Agarius campestris (Figure 3), or have both, as in Amanita muscaria, (Figure 4) and/or only have fruiting bodies, as in Kalahari truffle, Terfezia pfeilii (Figure 5). Furthermore, some mushrooms are in the form of pliable cups others are round like golf balls. Some are in the shape of small clubs some resemble coral others are yellow or orange jelly-like globs and some even closely resemble the human ear. In fact, their shapes and forms are countless, and their colors display all the elements of the rainbow. Their cell walls contain chitin, which also occurs in the exoskeleton of insects and other arthropods. They absorb O2 and release CO2. In fact, they may be more closely related to animal cells than plant cells (Baldauf, Roger, Wenk-Siefert, & Doolittle, 2000 Dal Campo & Ruiz-Trillo, 2013 Feeney, Dwyer, Hasler-Lewis, Milner, Noakes, Rowe, et al., 2014 Steenkamp, Wright, & Baldauf, 2006).

Figure 1. Lentinus edodes, a typical type of mushroom with pileus and stipe.

Figure 2. Volvariella volvacea, with pileus, stipe, and volva.

Figure 3. Agarius campestris, with pileus, stipe, and annulus.

Figure 4. Amanita muscaria, with pileus, stipe, an annulus, and also the bulbous base adorned with several concentric zones of white scales representing the volva.

Figure 5. Terfezia pfeilii, with fruiting body only.

Mushrooms are devoid of leaves and of chlorophyll-containing tissues. They are also devoid of vascular xylem and phloem. Therefore, they are incapable of photosynthetic food production, relying instead on organic matter synthesized by surrounding green plants including organic products contained in agricultural crop residues. The organic materials from which mushrooms derive their nutrition are referred to as substrates. They process their food by secreting degrading enzymes that serve as the key to unlocking and decomposing the complex food materials present in the biomass where they grow to generate simpler compounds, which can be absorbed and then transformed into fresh new mushroom tissues. Mushrooms lack true roots but anchor themselves instead through their tightly interwoven thread-like mycelia, which colonize the substrates, degrade their biochemical components, and siphon away the hydrolyzed organic compounds for their own nutrition. These substrate materials range from decomposing material in natural ecosystems, from the soil underlying forest floors to by-products and wastes from industry, households, and agriculture.

The structure that we call a mushroom is, in reality, only the fruiting body of the fungus. The vegetative part of the fungus, called the mycelium, comprises a system of branching threads and cord-like strands—called hyphae that branch out through the soil, compost, wood logs, or other lignocellulosic material, in which the fungus may grow. After a period of growth, and under favorable conditions, the established (matured) mycelium produces the fruit structure, which we call the mushroom. In terms of human utility, mushrooms can be grouped into four categories: (a) those that are fleshy and edible fall into the edible mushroom category, such as Agaricus bisporus (b) mushrooms considered to have medicinal applications, are referred to as medicinal mushrooms, such as Ganoderma lucidum (c) those that are proven to be or suspected of being poisonous are named poisonous mushrooms, such as Amanita phalloides and (d) a miscellaneous category, which includes a large number of mushrooms whose properties remain less well defined, may tentatively be grouped together as “other mushrooms.” Certainly, this approach of classifying mushrooms is not absolute and not mutually exclusive. Many kinds of mushrooms are not only edible but also possess tonic and medicinal qualities.

Mushrooms also can be classified into various ecological groups. The most important groups are saprophytic and soil-based (living on dead organic matter), mycorrhizal (symbiotic relationship with mushroom mycelia and roots of almost all green plants), lignicolous (living on wood of trees or other substances containing lignin some are found on living plants and are called parasitic), entomogenous (associated with insects), and coprophilous mushrooms (which grow on the dung of different animals).

Mushrooms and fungi in general are extremely abundant and diverse worldwide. Recent estimates of the number of fungi on Earth range from 500,000 to more than 5 million species, with a widely accepted working figure around 1.5 million, published in the early 2000s (Hawksworth, 2001). To date, it is recommended that as many as 3 million species of fungi should be accepted (Blackwell, 2011). Meanwhile, the total number of described fungi of all kinds is currently 110,000 species. The figure is based on the total reached by adding the number of species to each genus given in the last edition of the Dictionary of Fungi (Kirk, Cannon, David, & Stalpers, 2008) and other recent publications and includes all organisms traditionally studied by mycologists: slime molds, chromistan fungi, chytridiaceous fungi, lichen-forming fungi, filamentous fungi, molds, and yeasts. Out of these, mushrooms constitute 16,000 species, calculated from the Dictionary of Fungi and other publications of recent years (Hawksworth, 2012 Kirk et al., 2008 Wasser, 2010). But the actual number of mushroom species on Earth is currently estimated at 150,000–160,000, so only around 10% of existing mushroom species are known to science so far (Blackwell, 2011 Wasser, 2010). An analysis of the localities from which fungi new to science have been described and catalogued in the index of fungi in the last 10 years revealed that about 60% of all newly described fungi are from the tropics. This is also the case for mushrooms, especially those species forming ectomycorrhizas (symbiotic root associations) with native trees, although new species continue to be discovered in Europe and North America. In various tropical areas, 22–55% (in some cases up to 73%) of mushroom species have not yet been described (Hawksworth, 2012). Modern sequencing methods suggest that as many as 5 million species of fungi exist. Therefore, we would need more than 4,000 years to describe this fungal diversity based on the present discovery rate of about 1,200 new species per year, which has been an average for the last 10 years. Summarizing these data, we can assume that approximate 2% of world fungal biota and around 10% of world mushroom biodiversity have been discovered by mycologists to date, thus the bulk of fungal biodiversity still remains hidden.

Out of the 1.5 million estimated fungi species, Hawksworth (2012) estimated that 160,000 species produce fruiting bodies of sufficient sizes and suitable structures to be considered as macrofungi. These can be called mushrooms according to the above definition. Of the recognized mushroom species, about 7,000 species (50%) are considered to possess varying degrees of edibility, and more than 3,000 species from 231 genera are regarded as prime edible mushrooms (Wasser, 2002, 2010 Wasser & Weis, 1999). But only about 200 of the prime edible mushrooms are experimentally grown, 100 economically cultivated, around 60 commercially cultivated, and more than 10 produced on an industrial scale in many countries. Furthermore, of the 16,000 known mushroom species, approximately 700 are considered to be safe species with medicinal properties (Wasser, 2010). The number of poisonous mushrooms approximates 500 species. It should be specially emphasized that some wild unidentified mushrooms can be poisonous and lethal. Therefore, if you are not absolutely sure whether a given mushroom is edible or not, do not touch it! Leave the unknown mushroom alone!

The Cultivation of Mushrooms

Brief History of Mushroom Cultivation

Throughout recorded history there are repeated references to the use of mushrooms as food and for medicinal purposes, and it is not surprising that the intentional cultivation of mushrooms had a very early beginning. China can boast that it was the first to successfully cultivate many popular mushrooms species—for example, Auricularia auricula-judae (estimated date, 600 ad ), Flammulina velutipes ( 800–900 ad ), Lentinula edodes ( 1000–1100 ad ), Volvariella volvacea ( 1700 ad ), and Tremella fuciformis ( 1800 ad ). Prior to the 1900s, Agaricus bisporus ( 1650 ad in France) was the only major, commercially cultivated mushroom species that was not first cultivated in China (Chang & Miles, 2004). The extensive use of mechanized cultivation techniques for producing mushrooms in great quantities for food, like so many other large-scale agricultural activities, is a phenomenon of the 20th century . Agaricus bisporus has been a favorite mushroom in Western countries, where it is variously known as the button mushroom, the white mushroom, the cultivated mushroom, or champignon. Mushroom cultivation techniques were introduced from France to other European countries, to North America, and recently to countries throughout the world. Following World War II, there was a great spurt in the production of Agaricus, and the past few decades have also seen great increases in production of Lentinula, Flammulina, and Pleurotus and, to a lesser extent, Volvariella. (Chang & Buswell, 2008) The development of mushroom cultivation technology has been largely responsible for the increase in mushroom production. In the following section, many of the cultivation techniques are described that have been developed for different mushrooms in various parts of the world.

Principles of Mushroom Cultivation and Production

The cultivation of mushrooms ranges from a relatively primitive farming activity to a highly technological industry. In each case, however, continuous production of successful crops requires both practical experience and scientific knowledge. Mushroom cultivation is both a science and an art. The science is developed through research the art is perfected through curiosity and practical experience. Mushroom growth dynamics involve some developmental aspects, which are in consonance with those exhibited by our common agricultural crop plants. For example, there is a vegetative growth phase, in which the mycelia grow profusely, and a reproductive (fruiting) growth phase, when the umbrella-like body that we call a mature mushroom develops. In agricultural plants such as sunflowers, when the plants switch from the vegetative growth to the reproductive growth, any further growth of the tips is retarded, and the plant is said to be mature. After the vegetative (mycelial) phase has reached maturity, what the mushroom farmer needs to do next is referred to as the induction of fruiting. This is the time mycelial growth at the tips should be slowed down and redirected by regulating specific environmental factors. These factors, generally called “triggers” or “environmental shocks,” can be switching on the light, providing fresh air, lowering temperatures, spraying the mushroom beds with water, and in some cases, reducing nutrients to trigger fruiting (Figure 6).

Figure 6. The two major phases of mushroom growth and development: vegetative phase and reproductive phase (modified from Chang, 2001). The triggers for the transition from the vegetative phase to reproductive phase comprise the various environmental factors important for induction of fruiting. The two broken lines without labels could be nutritional factors or pH values, depending on the mushrooms cultivated.

Although the principles of cultivation are commonly similar for all mushrooms, the practical approaches can be quite different for different species cultivated. The approaches have to be modified and adjusted according to the local climatic conditions, materials available for substrates, and varieties of the mushroom used.

The Major Practical Steps of Mushroom Cultivation

Mushroom cultivation is a complex business requiring precision. Indeed, it is not as simple as what some people often loosely suppose. It calls for adherence to precise procedures. The major practical steps/segments of mushroom cultivation, as described by Chang and Chiu (1992), and Chang and Mshigeni (2013), are:

Selection of an acceptable mushroom species: Before any decision to cultivate a particular mushroom is made, it is important to determine if that species possesses organoleptic qualities acceptable to the indigenous population, or to the international market if the suitable substrates for cultivation are plentiful, and if environmental requirements for growth and fruiting can be met, without excessively costly systems of mechanical control.

Securing a good-quality fruiting culture: A “fruiting culture” is defined as a culture with the genetic capacity to form fruiting bodies under suitable growth conditions. The stock culture selected should be acceptable in terms of yield, flavor, texture, fruiting time, etc.

Development of a robust mushroom spawn: A medium through which the mycelium of a fruiting culture has grown and that serves as the inoculum of “seed” for the substrate in mushroom cultivation, is called the “mushroom spawn.” Failure to achieve a satisfactory harvest may often be traced to unsatisfactory spawn used. Consideration must also be given to the nature of the spawn substrate, since this influences rapidity of growth in the spawn medium, as well as the rate of mycelial growth and the filling of the beds following inoculation.

Preparation of selective substrate/compost: While a sterile substrate free from all competitive micro-organisms is the ideal medium for cultivating edible mushrooms, systems involving such strict hygiene are generally too costly and impractical to operate on a large scale. Substrates for cultivating edible mushrooms normally require varying degrees of pre-treatment to promote growth of the mushroom mycelia to the practical exclusion of other micro-organisms. The substrate must be rich in essential nutrients, in forms that are readily available to the mushroom, and also free of toxic substances that inhibit the growth of the spawn. Moisture content, pH, and good gas exchange between the substrate and the surrounding environment are important physical factors to consider.

Care of mycelial (spawn) running: Following composting, the substrate is placed in beds, where it is generally pasteurized by steam to kill off potential competitive microorganisms. After the compost has cooled, the spawn can either be sown over the bed surface, then pressed down firmly against the substrate to ensure good contact, or they can be inserted 2 to 2.5 cm deep into the substrate. “Spawn running” is the phase during which mycelia grow from the spawn and permeate into the substrate. Good mycelial growth is essential for mushroom production.

Fruiting/mushroom development: Under suitable environmental conditions, which may differ from those adopted for spawn running, natural germination occurs and is then followed by the production of fruiting bodies. The appearance of mushrooms normally occurs in rhythmic cycles called “flushes.”

Harvesting mushrooms carefully: Harvesting is carried out at different maturation stages, depending upon the species, and upon consumer preferences and market value.

If you ignore one critical step/segment, you are inviting trouble, which could lead to a substantially reduced mushroom crop yield and mushroom marketing value.

The Brief Background With References for Cultivation of a Few Selected Mushrooms

Mushroom cultivation involves a wide range of technologies. The choice of these technologies depends upon the species cultivated, substrates, capital available, etc. Examples of six representative mushroom species are presented here: Agaricus bisporus, Lentinula eddoes, Pleurotus pulmonarius var. stechangii, Volvariela volvacea, Agaricus brasilienesis, and Ganoderma lucidum. During the last three decades, in addition to Agaricus mushroom, many other species have been cultivated at a larger scale. In the 19th ISMS (The International Society for Mushroom Science) Congress held in the Netherlands from May 29 to June 2, 2016 , it was worth noting that of the nearly 120 lectures and presentations that were submitted, approximately half concerned mushrooms other than Agaricus bisporus mushroom (Wach, 2016).

Agaricus bisporus

Agaricus bisporus (champignon, button mushroom, Figure 7) is simply the most commonly cultivated mushroom. In Western countries, cultivation of this mushroom has developed over the past 500 years, but from the outset it was considered to be a risky venture to pursue as a predictable and controllable industrial process, particularly in France, Great Britain, and the Netherlands. The culture of this mushroom originated in Paris (France) in areas in which mushrooms were frequently obtained on used compost issued from melon crops. At a later date, it was observed that this mushroom could grow without light. Therefore, its successful culture was undertaken inside caves (Delmas, 1978). France continued to lead the world as mushroom grower until the outbreak of World War II in 1939 . From that time on, the United States has assumed the dominant position. The mushroom-growing method in standard house was developed and adopted by the English-speaking countries. Furthermore, in Western countries cultivation of Agaricus mushroom is a professional business, and for large-scale farmers it is an industrial enterprise. The improvements of cultivation techniques, for example, separating heat rooms from growing rooms, depth of beds, compost, spawn and spawning, casing, crop management, pest and disease control, harvesting, among others, not only greatly increased and stabilized the crop yield but also improved the mushroom quality. Another move was to use hybrid strains, which has enabled the growers to produce the quality mushrooms necessary for expanding domestic and export sales of fresh mushrooms. These innovative changes had to expand and to meet the changing needs of the markets. In no small measure, this remarkable achievement in modern mushroom industrial development may be attributed to contributions from vigorous research conducted at mushroom agricultural laboratories, centers, and stations. (e.g., P. B. Flegg and D. Wood, Glasshouse Crops Research Institute, Littlehampton, U.K. G. Fritsche and L. J. Van Griensven, Mushroom Research Institute, Horst, Holland D. J. Royse and I. C. Schisler, Department of Plant Pathology, Pennsylvania State University, Philadelphia, PA).

The specifics of this mushroom have been very well established through the repeating practical experiments of researchers like San Antonio (1975) Chang and Hayes (1978) Van Griensven (1988) Quimio, Chang, and Royse, (1990) and Kaul and Dhar (2007). The composting process for Agaricus cultivation is of particular interest here as a basic illustration of mushroom-based agriculture (Buth, 2016 Hayes, 1977 Hilkens, 2016 Nair, 1993).

Figure 7. Agaricus mushrooms grown on horse manure compost.

Generally, composting refers to the piling up of substrates for a certain period of time and the changes due to the activities of various microorganisms, which result in the composted substrate becoming chemically and physically different from the starting material. This is sometimes referred to as a solid-state fermentation. Two types of composting are commonly described. One type involves the decomposition of heaps of organic wastes and the subsequent application of the residue to the soil. The aim of this type of composting is to reduce, in a sanitary manner, both the volume and the carbon and nitrogen ratio of the organic waste so that is it suitable for manuring the soil to improve the growth of plant crops. When given directly to the soil without composting, organic waste with a high C:N ratio (such as straw) can give rise to a temporary nitrogen deficiency, which will then result in a reduction in yield of the plant crop.

The role of second type of composting is the production of a selective substrate that will preferentially support the growth of the mycelium of the mushroom. The basis of this selectivity, however, cannot be attributed to one factor or one aspect of the entire system. The physical, chemical, and biological aspects of composting are fundamentally interrelated, but can be artificially separated for the convenience of investigation and discussion.

Mushroom growers use their sense of sight, smell, and touch to evaluate the progression of the composting process and the quality of the final product. The gross characteristics of compost, usually referred to as “structure,” result from a number of complex physical, chemical, and microbial processes that comprise composting (Nair, 1993).

Composting is prepared in accordance with well-documented commercial procedures (Chang & Hayes, 1978 Kaul & Dhar, 2007 Van Griensven, 1988). In Phase I of the process (outdoor composting), locally available raw materials are arranged into piles, which are periodically turned and watered. The initial breakdown of the raw ingredients by microorganisms takes place in Phase I. This phase is usually complete within 9 to 12 days, when the materials have become pliable, dark brown in color, and capable of holding water. There is normally a strong smell of ammonia. The aeration—a good supply of oxygen—has been recognized recently to be significantly important in phase I compost (Buth, 2016). Phase II (indoor fermentation) is pasteurization, when undesirable organisms are removed from the compost. This is carried out in a steaming room where the air temperature is held at 60°C for at least 4 hours. The temperature is then lowered to 50°C for 8 to 72 hours, depending upon the nature of the compost. CO2 is maintained at 1.5 to 2%, and the ammonia level drops below 10 PPM. Following Phase II composting, the substrate is cooled to 30°C for A. bitorquis and to 25°C for A. bisporus for spawning. Production of Phase III or Phase IV composts for growing Agaricus mushrooms has been an advanced technological development in recent years in Western countries. The production of Phase III compost is Phase II compost spawn run in a bulk tunnel, and ready for casing when delivered to the grower. If the Phase III compost is then cased, and spawn develops into a casing layer before dispatching to the growing unit or delivering to growers, it is named as Phase IV compost. The successes of bulk Phase III and Phase IV depend a lot on the quality of Phase I and Phase II processes.

Phase II composting undertaken on shelves produces an average of 4.1 crops per year. Since 1999 , growers using Phase III production have enjoyed an average of 7.1 crops per year. In recent years, Phase IV can generate 10–12 crops per year (Dewhurst, 2002 Lemmers, 2003). So, good compost is vital for supporting cultivation and represents 85% of the power behind mushroom production (Heythuysen, 2015).

Lentinula edodes

Lentinula edodes (Xiang-gu, shiitake, oak mushroom, Figure 8) is one of the most important edible mushrooms in the world from the standpoint of production, and it is the most popular fungus cultivated in China, Japan, and in some other Asian countries. For a long time, this mushroom has been valued for its unique taste and flavor and as a medicinal tonic. It can be cultivated either on wood log or on synthetic substrate logs (Chang & Miles, 2004 Quimio et al., 1990 Stamets, 2000).

Figure 8. Lentinula edodes grown on sawdust synthetic logs.

Lentinula edodes is a kind of wood rot fungus. In nature, it grows on dead tree trunks or stumps. In general, the wood for the mushroom growth consists of crude protein, 0.38% fat, 4.5% soluble sugar, 0.56% total nitrogen, 0.148% cellulose, 52.7% lignin, 18.09% and ash, 0.56%. Generally speaking, the C/N in substrate should be in the range from 25 to 40:1 in the vegetative growth stage and from 40 to 73:1 in the reproductive stage. If the nitrogen source is too rich in the reproductive phase, fruiting bodies of the mushroom are usually not formed and developed.

The optimum temperature of spore germination is 22–26 ºC. The temperature for mycelial growth ranges from 5–35 ºC, but the optimum temperature is 23–25 ºC. Generally speaking, L. edodes belongs to low temperature mushrooms, the initial and development temperature of fruiting body formation is in the range of 10–20 ºC, and the optimum temperature of fructification for most varieties of the mushroom is about 15 ºC. Some varieties can fruit in higher temperatures, 20–23 ºC. These high temperature mushrooms usually grow faster and have a bigger and thinner cap (pileus), and a thin and long stalk (stipe). Their fruiting bodies are easily opened and become flat grade mushrooms, which are considered to be low quality. The optimum pH of the substrate used in making the mushroom bag/log is about 5.0–5.5 (Chang & Miles, 2004 Stamets, 2000).

Culture media and preparation: The mushroom can grow on a variety of culture media and on different agar formulations, both natural and synthetic, depending on the purpose of the cultivation. Synthetic media are often expensive and time consuming in preparation hence they are not commonly used for routine purposes.

The potato dextrose agar, or PDA, is the simplest and the most popular medium for growing the mycelium of the mushroom. It is prepared as follows:

Ingredients: Diced potato 200 gm dextrose (or ordinary white cane sugar), 20 gm powdered agar (or agar bars), 20 gm and distilled water (or tap water) 1 liter.

Procedure: Peeled potatoes are washed, weighed, and cut into cubes. They are boiled in a casserole with at least one liter of water until they become soft (around 15 minutes). The potatoes are removed, and water is added to the broth to make exactly 1 liter. The broth is returned to the casserole and dextrose and the agar added. The solution is heated and stirred occasionally until the agar is melted. The hot solution is then poured into clean flat bottles. For pure or stock cultures, the test tubes are filled with at least 10 ml of the liquid agar solution. The bottles or test tubes are plugged with cotton wool. When Petri dishes are available, these can be used to produce mycelial plugs for inoculation of mother spawn.

The L. edodes mushroom is produced on both cottage and commercial scale. The following section outlines some of the issues associated with the different cultivation styles.

Cottage scale cultivation: There are many formulas for the composition of the substrate. The ingredients can vary from place to place and country to country depending upon the raw materials available and local climatic conditions. In general, after mixing the dry ingredients by hand or with a mechanical mixer, water is added to the mixture so that the final moisture content of the substrate is between 55% and 60%, depending on the capacity of the sawdust to absorb water. The ingredients are then packed into autoclavable polypropylene or high-density polyethylene bags. Although they are more expensive, polypropylene bags are the most popular since polypropylene provides greater clarity than polyethylene. After the bags have been filled (1.5 to 4 kg wet wt.) with the substrate, the end of the bag can be closed either by strings or plugged with cotton wool stopper. Four formulas in the preparation of the substrate for the cultivation of the mushroom are given here as reference: (a) Sawdust 82%, wheat bran 16%, gypsum 1.4%, potassium phosphate, dibasic 0.2%, and lime 0.4% (b) Sawdust 54%, spent coffee grounds 30%, wheat bran 15%, and gypsum 1% (c) Sawdust 63%, corncob powder 20%, wheat bran 15%, calcium superphosphate 1%, and gypsum 1% (d) Sawdust 76%, wheat bran 18%, corn powder 2%, gypsum 2%, sugar 1.2%, calcium superphosphate 0.5%, and urea 0.3%.

Commercial scale cultivation: In general, the operation can use oak or other hard wood sawdust medium to grow the mushroom. The basic steps are (a) to mix the sawdust, supplements, and water (b) bag the mixture (c) autoclave the bags to 121ºC and cool the bags (d) inoculate and seal the bags (e) incubate for 90 days to achieve full colonization of the sawdust mixture, in other words, to allow the mycelium be established for ready fructification (f) fruit the colonized and established sawdust logs/bags/blocks 6 times using a 21 days cycle at 16 to 18ºC and (g) harvest, clip steps, grade, box, and cold store for fresh market, or harvest, dry, cut steps, grade, and dry again before box for dry market.

Major equipment used in production consists of mixer/conveyor, autoclave, gas boiler, cooling tunnel, laminar-flow cabinet, bag sealer, air compressor for humidification, shelves to incubate.

Incubation can be done in two rooms and in two shipping containers. The two shipping containers can be installed near the fruiting rooms. Temperature during incubation is held between 18 and 25 ºC.

Fruiting can be done in six rooms so that the blocks/logs can be moved as a unit. With compartmentalization, blocks in each room can be subjected to a cycle of humid cold, humid heat, and dry heat.

Pleurotus pulmonarius var. stechangii

Pleurotus pulmonarius var. stechangii (=P. sajor-caju) (Chang’s oyster mushroom) is comparable to the high temperature species in the group of Pleurotus (oyster) mushrooms, with high temperatures required for fructification. This mushroom has a promising prospect in tropical and subtropical areas. Its cultivation is easy with relatively less complicated procedures (Chang & Miles, 2004 Kaul & Dhar, 2007 Zmitrovich & Wasser, 2016, Figure 9).

Figure 9. Pleurotus pulmonarius var. stechangii grown on cereal straw substrate.

The temperature for growth of mycelium is 10–35 ºC. The optimum growing temperature of the mycelium is 23–28 ºC. The optimum developmental temperature of the fruiting body is 18–24 ºC. The optimum pH of the substrate used in making the mushroom bag/bed is 6.8–8.0. The C/N ratio in the substrate is in the range of 30–60:1. A large circulation of air and reasonable light are required for the development of the fruiting bodies.

Spawn substrate: (a) wheat grain + 1.5% gypsum or lime (b) cotton seed hull, 88% wheat bran, 10% sugar, 1% and gypsum, 1% (c) sawdust, 78% wheat bran, 20% sugar, 1% and gypsum, 1% (d) sawdust, 58% spent coffee grounds/spent tea leaves, 20% water hyacinth/cereal straw, 20% sugar, 1% and gypsum, 1%.

Cultivation substrate: (a) cotton seed hull, 95% gypsum, 2% lime, 1% and calcium superphosphate, 2% (b) rice straw, 80% cotton waste, 18% gypsum, 1% and lime, 1% (c) water hyacinth, 80% cereal straw 17%, gypsum, 2% and lime, 1%.

For demonstration purpose, this mushroom can be nurtured to grow into a tree-like shape (Figure 10). The cultivation method, which has been tested successfully, is as follows: Cotton waste or rice straw mixed with water hyacinth is used as the substrate. Tear large pieces of cotton waste into small parts or cut the straw and water hyacinth into small segments. Add 2 % (w/w) lime and mix with sufficient water to get moisture content of about 60–65%. Pile the materials up, cover with plastic sheets, and leave to stand overnight. Load the substrate into small baskets or onto shelves for pasteurization, or cook the substrate with boiled water for 15 minutes. After cooling to approximately 25 ºC, mix around 2% (w/w) spawn thoroughly with the substrate and pack into columns of 60-cm-long tubes that have hard plastic (PVC) tubing of 100 cm (4 cm in diameter) as central support, and plastic sheets as outside wrapping (Chang, Lau, & Cho, 1981).

Figure 10. Robust growth of Pleurotus pulmonarius var. stechangii as a mushroom tree.

Incubate these columns at around 24 to 28 ºC, preferably in the dark. When the mycelium of the mushroom has ramified the entire column of substrate after three to four weeks, remove the plastic wrapping and switch on white light. Watering is needed occasionally, to keep the surface from drying. In around three to four days, white primordia start to appear over the whole surface. After another two to three days, the Pleurotus mushrooms are ready for harvesting. During the cropping period, watering is very important if many flushes are required.

Volvariella volvacea

Volvariella volvacea (patty straw mushroom, Chinese mushroom, Figure 11) is a fungus of the tropics and subtropics and has been traditionally cultivated in rice straw for many years in China and in Southeast Asian countries (Chang, 1965). In 1971 , cotton wastes were first introduced as heating material for growing the straw mushroom (Yau & Chang, 1972). In 1973 , cotton wastes had completely replaced the traditional paddy straw for growing mushrooms (Chang, 1974). This was a turning point in the history of straw mushroom cultivation because the cotton waste compost through the pasteurization process brought the cultivation of the mushroom to an industrial scale—first in Hong Kong and then in Taiwan, Thailand, and China. Several techniques are adopted for the cultivation of the mushroom, which thrives in temperature ranges of 28 to 36 ºC and a relative humidity of 75–85%. Detailed descriptions of the various methods are given by Chang and Miles (2004), Kaul and Dhar (2007), and Quimio et al. (1990). Choice of technologies usually depends on personal preference, on the availability of substrates, and the amount of resources available. While more sophisticated indoor technology is recommended for industrial-scale production of the mushroom, most other technologies are low cost and appropriate for rural area development, especially when production is established at the community level.

Figure 11. Different stages of fruiting bodies of the straw mushroom (Volvariella volvacea) grown on cotton waste as substrate.

Agaricus brasiliensis

In recent years, A. brasiliensis (Royal Sun Agaricus, Himematuatake, Figure 12), formerly called A. blazei Murrill (Wasser, Didukh, Amazonas, Nevo, Stamets, & da Eira, 2002) has rapidly become a popular mushroom. It has proven to be not only a good tasting and highly nutritious mushroom but also an effective medicinal mushroom, particularly for anti-tumor active polysaccharides.

Figure 12. Different stages of Agaricus brasiliensis mushroom grown in straw compost with case soil.

A. brasiliensis originated as a wild mushroom in southeastern Brazil, where it was consumed by the people as a part of their diet. The culture of the mushroom was brought to Japan in 1965 , and an attempt to cultivate this mushroom commercially was made in 1978 . In 1992 , this mushroom was introduced to China for commercial cultivation (Chang & Miles, 2004).

A. brasiliensis belongs to the so-called middle temperature mushrooms. The growth temperature for mycelium ranges from 15 to 35 ºC and the optimum growth temperature ranges from 23 ºC to 27 ºC. The temperature for fruiting can be from 16 ºC to 30 ºC, and the optimum developmental temperature of fruiting bodies is 18 ºC to 25 ºC. The ideal humidity for casing soil is 60–65%. The air humidity in a mushroom house prefers 60–75% for mycelium growth and 70–85% for fruiting body formation and development. The optimum pH of the compost used in making the mushroom bed is 6.5–6.8. The optimum pH of the casing soil is 7.0. A good circulation of air is required for the development of the fruiting bodies. These conditions are similar to those needed for the cultivation of A. bisporus. Under natural conditions, the mushroom can be cultivated for two crops each year. Each crop can harvest three flushes. According to the local climates, the farmer can decide the spawning time in the year in order to have mushrooms for harvest within 50 days after spawning.

Preparation of mushroom bed (Stamets, 2000): A. brasiliensis is a kind of mushroom belonging to the straw-dung fungi and prefers to grow on substrate rich in cellulose. The waste/by-productive agro-industrial materials, such as rice straw, wheat straw, bagasse (squeezed residue of sugar cane), cotton seed hull, corn stalks, sorghum stalk, and even wild grasses, can be used as the principal component of the compost for cultivation of the mushroom. It should be noted that these materials have to be air dried first and then mixed with cattle dung, poultry manure, and some chemical fertilizers. The following formulas for making compost are for reference only. They should be modified according to the local available materials and climatic conditions: (a) rice straw, 70% air-dry cattle dung, 15% cottonseed hull, 12.5% gypsum, 1% calcium superphosphate, 1% and urea, 0.5% (b) corn stalks, 36% cottonseed hull, 36% wheat straw, 11.5% dry chicken manure, 15% calcium carbonate, 1% and ammonium sulphate or urea, 0.5% (c) rice straw, 90.6% rice bran, 2.4% fowl droppings, 3.6% slaked lime, 1.9% superphosphate, 1.2% and ammonium sulphate/urea, 0.3% (d) bagasse, 75% cottonseed hull, 13% fowl droppings, 10% superphosphate, 0.5% and slaked lime, 1.5%.

Ganoderma lucidum

Although the medicinal value of G. lucidum (lingzhi, Reishi, Figure 13) has been treasured in China for more than 2,000 years, the mushroom was found infrequently in nature. This lack of availability was largely responsible for the mushroom being so highly cherished and expensive. During ancient times in China, any person who picked the mushroom from the natural environment and presented it to a high-ranking official was usually well rewarded (Chang & Miles, 2004).

Figure 13. The fruiting bodies of Ganoderma lucidum grown on short-wood segments that were then buried in the soil base for fruiting.

Artificial cultivation of this valuable mushroom was successfully achieved in the early 1970s and, since 1980 and particularly in China, production of G. lucidum has developed rapidly. Currently, the methods most widely adopted for commercial production are the wood log, short wood segment, tree stump, sawdust bag, and bottle procedures (Chang & Buswell, 1999 Stamets, 2000 Hsu, 1994 Mizuno et al., 1995).

Log cultivation methods include the use of natural logs and tree stumps, which are inoculated with spawn directly under natural conditions. The third alternative technique involves the use of sterilized short logs, about 12 cm in diameter and approximately 15 cm long, which allow for good mycelial running. This method provides for a short growing cycle, higher biological efficiency, good quality of fruiting bodies, and consequently, superior economic benefit. However, this production procedure is more complex and the production costs much higher than natural log and tree stump methods. For this production procedure, the wood logs should be prepared from broad-leaf trees, preferably from oak. Felling of the trees is usually carried out during the dormant period, which is after defoliation in autumn and prior to the emergence of new leaves the following spring. The optimum moisture content of the log is about 45–55% .The flow-routine for the short-log cultivation method is as follows: selection and felling of the tree sawing/cutting the log into short segments transference of segments to plastic bags sterilization inoculation spawn running burial of the log in soil tending the fruiting bodies during development from the pinhead stage to maturity harvesting of the fruiting bodies drying of the fruiting bodies by electrical driers packaging. It should be noted that the prepared logs/segments are usually buried in soil inside a greenhouse or plastic shed. The soil should allow optimum conditions of drainage, air permeability, and water retention, but excessive humidity should be avoided.

Examples of cultivation substrates, using plastic bags or bottles as containers, include the following (please note that these examples are for reference purposes only and can be modified according to the strains selected and the materials available in different localities): (a) sawdust, 78% wheat bran, 20% gypsum, 1% and soybean powder, 1% (b) bagasse, 75% wheat bran, 22% cane sugar, 1% gypsum, 1% and soybean powder, 1% (c) cotton seed hull, 88% wheat bran, 10% cane sugar, 1% and gypsum, 1% (d) sawdust, 70% corn cob powder, 14% wheat bran, 14% gypsum, 1% and cereal straw ash, 1% (e) corn cob powder, 78% wheat/rice bran, 20% gypsum, 1% and straw ash, 1%. After sterilization, the plastic bags can be laid horizontally on beds or the ground for fruiting.

Rapid Expansion of the Mushroom Industry in the Late 20th Century

It has been noted that a nutritious balance of foods and an active lifestyle in a friendly environment, can help achieve optimal health throughout life. The use of mushrooms as diet therapy to sustain or improve health or treat illness was used by ordinary people and in the imperial court of China as far back as 2,000 years ago (Xue & O’Brien, 2003). The pyramidal model of mushroom uses (Figure 14) conforms fully to an old Chinese saying “Medicine and food have a common origin.” This statement is particularly applicable to mushrooms, whose nutritional qualities and tonic effects as nutriceuticals (Chang & Buswell, 1996) or as dietary supplements (DSs) and medicinal attributes have long been recognized (Wasser, 2010). Human health may be divided into three states: health, sub-health, and illness. Mushrooms can be used mainly as food for a healthy state, as a medicine for illnesses, and as DSs for a sub-healthy state, as well as for both healthy and ill states (Chang & Wasser, 2012).

Figure 14. A pyramid model of mushroom uses (industry).

Since the end of World War II, mushroom production has increased steadily in agricultural-based industries. World production of cultivated edible mushrooms over a number of years is shown in Table 1. In 1981 , production totaled 1,257.2 thousand tons and in 1986 , 2,182.0 thousand tons, a 73.6% increase. By 1990 , total production was 3,763.0 thousand tons, increasing to 6,158.4 thousand tons by 1997 . Overall, world mushroom production increased over 12% annually during the period from 1981 to 1997 . However, the Agaricus mushrooms decreased in percentage of world total production. This is mainly due to other alternative edible mushrooms becoming more in demand for instance, Lentinus edodes increased in percentage of total global mushroom consumption, from 14.3% in 1981 to 25.2% in 1997 , and in production, from 180 thousand tons to 1,564.4 thousand tons. Pleurotus mushrooms increased from 2.8% to 14.2%, and their production increased from 35 thousand tons to 875.6 thousand tons, with a 25-fold increase over the same period of time. Auricularia mushrooms increased from 0.8% in 1981 to 7.9% in 1997 , and their production increased from 10,000 thousand tons in 1981 to 485.6 thousand tons in 1997 , with a 48.5-fold increase (Chang & Wasser, 2012). Overall, increase in world mushroom production has been due mainly to contributions from countries with developing economies including China, India, Poland, and Hungary. In contrast, mushroom production in Western European countries, the United States, and Japan, has remained unchanged or has even fallen. China especially has witnessed a huge increase in edible mushroom cultivation and now makes the largest contribution, by over 85%, to the total worldwide output (Table 2). Furthermore, several new species of mushrooms have been recently cultivated and marketed in China. India’s annual production of mushrooms doubled, from 5,000 tons in 2001 to 10,000 tons in 2004 , and is expected to continue rising, at about 25% per annum, for the foreseeable future. In Latin America, the annual mushroom production has also increased steadily since 1995 . During the period 1995–2001 , the estimated commercial mushroom production level in this region rose by 32% (49,975 to 65,951 tons), equivalent to an annual increase of 5%. Since mushroom cultivation can be a labor-intensive agro-industrial activity, it could have great economic and social impact by generating income and employment for both women and youth, particularly in rural areas in developing countries. Using China as an example, in 1978 the total production of mushrooms in China was only 60 thousand tons, which accounted for less than 6% of total world mushroom production. In 2012 (Table 2), however, total production of mushrooms in China reached 28.3 million tons, which accounted for more than 85%. By 2013 (Royse, Baars, & Tan, 2017), world production of cultivated edible mushrooms had increased to 34 million tonnes. China is the main producer of mushrooms, producing over 30 million tons. This accounted for about 87% of total production. The rest of Asia produced about 1.3 million tons, while the European Union, the Americas, and other countries produced about 3.1 million tons. In the same report, Lentinula edodes is the major species, contributing about 22% of the world’s cultivated mushrooms. Pleurotus spp, including 5 to 6 cultivated species, contributes about 19%, and Auricularia spp, including 2 to 3 species, contributes 17%, while Agaricus bisporus mushroom is responsible for 15% of the volume. Moreover, according to Feeney et al. (2014), since 2009 , China has produced 65% of global mushrooms and truffles, the European Union 24%, the United States 5%, and Japan, Indonesia, and Canada 1% each. Exact figures of world production of mushrooms are actually difficult to obtain, because some estimated figures are the total weight of all kinds of mushroom products including fresh, dried, and canned. That is incorrect. Technically, however dried, canned, and other preserved products should first be converted to the equivalent fresh weight and then added together.


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