(f) Advantages of synthetic compost
Synthetic compost is comparable with natural compost because it is capable of producing perfectly normal yields, sometimes even superior yields because of better aeration within the bed. However, horse-manure compost because it is cheaper is still the most-favoured substrate with the growing units in Europe and America. The main drawback in horse-manure is that its quality varies and this results in inconsistent yields. The natural compost is not pasteurized as per requirements, will tend to build up temperature within the bed which is detrimental to spawn run; also pests and diseases become active in such a compost. With the scarcity of horsedung, the synthetic compost is bocoming increasingly popular in many mushroom-growing countries, especially in the far-East. Synthetic compost is more uniform in quality and texture and supports better spawn run, since the bed is bettet aerated. However, such a compost tends to dry up rather quickly when the atmosphere turns dry. The actual time of composting a synthetic compost is about a week longer than that required for composting horse-manure in the normal way by the long method.
(g) Method of composting
There are two methods for preparing mushroom compost, the long and short method. The 'long method' is considered primitive and unsuitable for commercial cultivation. The 'short method' is quick and a definite advance over the earlier technology. However, the 'long method' is still relevant for the growers in India who cannot afford the expensive technology required for the short method.
Composting yard. The compost should be prepared near the growing site, on clean concrete or pucca floor at a higher level to prevent the run-off water collecting near the heap. Composting is usually done in the open, but it has to be protected from rain, by covering it with polythylene sheet. It can also be carried out in a shed with open sides to shelter it from rain.
(h) Composting procedure by long method
(i) Wetting the straw. The first step in the composting process is to wet straw. Fresh dry straw resists water absorption, and unless it is persuaded to absorp water, it will not soften; and unless it softens it will not take more water later. In practice, the straw is spread thinly over the entire floor of the composting yard. It is then gradually wetted by sprinkling water, gently, till the straw takes no more water. The straw is then turned for even wetting. Again water is sprinkled till it can absorb no more. At this stage, the water content is 75% and for the composts this point is reached when the compost is just saturated and before any run-off occurs. One ton of dry straw will requirealmost 5,000 litres of water to bring it into saturation.
(ii) Mixing and heaping. After the straw is wetted, the supplements excluding the gypsum are uniformally scattered over the straw and mixed. Some growers prefer to mix half the supplements at the beginning of composting, and the remaining half after the first turn. It is not known whether this practice is in any way beneficial. After mixing, the mixture is finally stacked in a heap. A heap one meter high, one meter wide and of indefinite length has been found to be suitable for Delhi during September-October. The straw can be stacked manually or with a stack mould. The straw should be firmly but not compactly compressed into the mould. The dimensions of the heap can be adjusted according to the size of straw and air temperature. The principle is that longer the straw, bigger the heap. If composting is done in the cooler months when the temperature ranges between 100 and 180C, a small heap would be unable to retain heat and moisture and the composting would be unsatisfactory. During the hot weather generally and in particular in tropical and sub-tropical regions, the temperature difference between inside of the compost and the surrounding air is too small to produce chimney-effect necessary for compost ventilation. Core ventilation does not take place. as a rule undesirable acid zones occur inside the compost. In such cases, relatively narrow heaps would be more suitable.
(iii) Turning schedule. It is important to ensure that the heap attains sufficiently high temperatures (700-750C) to bring about the correct composting, otherwise the compost will lack the necessary nutritive value so essential for a good crop. Care must also be taken to see that overcomposting does not take place. Open the heap and make it a number of times and for this purpose, the time schedule is suggested is :
| Day zero |
Wet, mix the stack the heap |
| 4th day |
First turning |
| 8th day |
Second turning |
| 12th day |
Third turning |
| 16th day |
Fourth turning |
| 20th day |
Final turning and filling of the trays |
Nitrogeneous supplements and carbohydrates are mixed on day zero. Gypsum is usually mixed at the third and forth turning in quantities. During the final turning, 40 ml Malathion diluted in 20 litres of water is sprinkled. any other available insecticide, like DDT, BHC or Lindane can also be used. The above schedule has been worked out on the basis of author's experience and can be altered if the conditions within the heap so require. The guiding principle is that the heap should be opened when the temperature within rises no further. For horsedung manure, the final turning is given is given on day rather than on day 20.
(i) Composting by short method
The method which was developed by Sinden and Hauser (1950) constitutes a general advance in controlled composting. The short method consists of two phases : phase I and phase II. The procedure for phase I is similar to the initial stages of the long method except, thatturnings are given sooner, the first on day 3, the second on day 6 and the third day on 9 or 10 when gypsum is added. The compost is now ready for the phase II or the peak heating.This is recognised as the microbial-composting stage and is an integral part of the total composting process. One aspect of the phase II is to promote such conditions in which the pasteurization of the compost. BY heating the compost and the surrounding air, for a brief periodof temperatures of about 600C, virtually all important parasites and pathogens can be eliminated.
