REPORT ON MUSHROOMS (September-October 1995)

George Chan - Consultant to ZERI-BAG Pilot Projects

During my recent trip to China for an Integrated Sewage Farm project for the Hamburg Environment Institute (HUI), I spent an aggregate of 7 days to look at Mushroom Culture, using alternative methods to what are usually practised in other countries. I saw mushroom installations and cultures in Guangdong, Hangzhou and Fujian.

Mushroom culture in China emphasizes the utilisation of crop residues to produce a high-value product (price- and protein-wise), with the compost used as more digestible and enriched feed or fertilizer. Not only are all the crop and processing residues (rice & wheat straw, rice & wheat bran, cottonseed meal, corncob, bagasse, molasses, sawdust, etc.) and even newspapers utilized, but more than a dozen varieties of special JUN grass are now planted for this purpose because they can replace the sawdust and rice or wheat bran which can then be used for other purposes.

The biggest breakthrough, which distinguishes the Chinese technologies from the rest of the world, is the culture of button mushroom (Agaricus bisporus) which usually requires big investment in costly buildings with controlled environment, and complex processes. In China, the farmers do it in bamboo & mud buildings, without artificial ventilation or lighting in a variety of substrates which require NO external input. Some potash and phosphate, used in the past, are now being replaced with digester sludge. Experiments are being carried out with digester effluent for the same purpose; and with brewery and distillery solid wastes to replace the soil used for the casing so that the residual compost can be used as livestock feed, presently inadequate on integrated farms, rather than fertilizer which is in abundance.

Mushroom is grown by individual or extended family farms in the suburbs in brick & tile buildings covering 200-400m2. The spawns are bought in bottles from a government station, and the strains are chosen for their high yield and disease resistance. There is a shortage of rice straw in the province, so it is mixed with the more available sawdust, cottonseed meal and newspaper. The mixture is sterilized by steaming, which is labour-intensive. Rice bran, sugar, manure (when available) and/or some agrochemicals are added to enrich the substrate which is then put in plastic bags with each end gathered together in a special ring to leave an area of 3cm diameter open. The spawns are put in these openings where the mushrooms grow. The plastic bags are stacked in 5-6 layers, one perpendicular to the other, but usually reduced to three which is considerd to be more effective. Enough space is left between the stacks to allow the workers to walk. The mushrooms grown are usually 2-3 kinds of oyster (Pleurotus spp) in the cold season and straw (Volvariella volvaceae) when it is warmer. Sometimes shitake (Lentinus edodes) is also grown, depending on the spawns being available.

The farm I visited had 400m2 of buildings, using 10,000 bags yearly with each bag producing 1 kg of mushrooms within 30 days of fruiting, which is equivalent to 10 Tons valued at US$8,000 -- a very good income for a family in China. The substrate is only used once, and the compost is sold to a nearby farmer growing soyabeans.

In Hangzhou, Capital of Zhejiang province, where I went for HUI to look at sewage and livestock waste treatment and nutrient recycling, and aquaponic culture on fish ponds, I also discussed the culture of various kinds of mushroom with the Director of the Hangzhou Research Institute of Energy & Environment. He has been involved with mushroom culture before he became Director of the Waste Recycling programme in towns, on farms and in agroindustries.

His biggest breakthrough is to grow button mushroom (Agaricus bisporus) on the traditional substrate of crop residues, BUT with the digester sludge to replace raw or composted manure and agrochemicals, and without the capital intensive and modern infrastructure requiring controlled environment and complicated processes of other countries. Unfortunately, I could only see the photos which I could not copy because my automatic camera got stuck at that crucial moment!

This mushroom is usually cultured in autumn for 3 months and between winter and spring for another 3 months. There was also not enough time for me to see the installations because I had to visit various farm and sewage treatment plants.

I was also told that in Jiangxi, which is next to Guangdong province but inland, shitake is grown year-round under rudimentary conditions, and their "flower" variety is the most famous in China and as good, if not better, than the best Japanese ones but are much much cheaper. I will certainly visit it during my next trip to China.

Fujian is the Mushroom Province of China, with 25% of China's production and 10% of the world's total. Half the mushrooms is button and some shitake, and the other half is made up of straw, oyster and wood's ear. The mushroom industry started 20 years ago with a fully equipped research institute to look for the proper strains of disease resistant mushrooms to be grown by peasants with the simplest methods possible. Among other things they have succeeded in finding the right strains of buttom mushroom which can grow during 2 periods of 3 months each per year in simple buildings made of bamboo, clay and straw, with no air conditioning, heating or lighting. As mentioned above, they use the strains to suit the climatic conditions, and grow them on 5 to 6 shelves in a high building. They are grown on the shelves with 20cm of compost made of 2 parts rice straw and 1 part cow manure, mixed with some potash and phosphate and covered with a casing of soil, to produce 1 part mushroom. The growing seasons are October-December and March-May, with the harvesting period of 45 days every time. The residual compost can only be used as fertilizer because it is difficult to separate the soil from the rest.

The oyster mushrooms have many varieties, producing the same quantity as the buttom mushroom: 30-40% of the weight of the substrate, but there are 3 of them which produce 200-300%, with the best one being Pleurotus ostreatus. They are produced in plastic bag too, but somewhat different from that used in Guangdong. The spawns are mixed with the substrate, and the ends of the plastic bag are tied up completely, making the work much easier than with the rings. When the fruiting starts, the young plants pierce the plastic, and the ends are then cut off. Sometimes, even other parts of the plastic are pierced, but the mushrooms are just left to grow.

The button mushroom farm I visited is in Zuqi town, Minhou county, and the growing area is 7,000m2, producing 70 tons half-yearly which are sold to a local cannery. This farm can grow other kinds of mushroom during the other 6 months but prefer to concentrate on the button ones, and leave its personnel to do other things during that period. Fujian has 50 canneries in all to deal with the whole production of button mushrooms and asparagus in the province.

The smaller farms grow mushrooms during the whole year, and the total area for the province is 300,000m2. Some of them are growing special JUN grass for use as substrate as more farmers are shifting from rice to other crops for higher income per unit surface, particularly on the increasing number of integrated farms. It is claimed that the JUN grass ia a richer substrate, so the quantity can be reduced, and the mushrooms grown on it are more nutritious.

I would like to suggest the following modifications to the Chinese institutions, and I would certainly try them in the ZERI pilot projects:

    1. Have the plastic bags, used for oyster mushrooms, on shelves made of bamboo to increase the growing areas instead of stacking them on the ground.
    2. Have a system of stands made with bamboo on the shelves to allow the mushroom to grow on a larger area on every bag.
    3. Put the cow manure in a digester instead of leaving it to dry in open air, losing some ammonia, before mixing it with the straw. Then use the digester sludge and effluent to treat the straw as shown below.
    4. Let the straw soak in the digester effluent for a few days and leave it to ferment for a while before using it for mushroom culture.
    5. Mix the straw in 4 (above) with the digester sludge instead of purchasing chemical potash and phosphate.
    6. Replace the soil used for casing with solid wastes from breweries and distilleries, containing valuable spent grains, so that the residual compost can be used as high-value livestock feeds.

There is no doubt that mushroom culture can be a very important process of the ZERI-BAG concept, especially NOW that we know it can all be done without the constraints which have been put forward by many of our experts.

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