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Abstract: The history of mushroom research shows a lot of work on the clarification of the role of nitrogen in the compost (reviews by Bohus, 1959; Flegg, 1961 and further MacCanna, 1969; O'Donoghue, 1967; Bech and Rasmussen, 1969). Later on the carbon sources were also taken into consideration to an increasing extent (Gerrits et al., 1967; Hayes and Rändle, 1967). Many research workers have analyzed compost (Grabbe, 1972) to look for a relationship between some factor and mushroom yield. This is difficult because a compost is such a complicated chemical and physical system. The C/N ratio of the compost is often used as an important figure to charactenze a compost. As the C/N ratio is considered to be the ratio of all the carbon to all the nitrogen in the compost, in fact this representation of the matter is too simple. The total amount of carbon includes all kinds of carbon from readily available to available with great difficulty. The same applies to the nitrogen which is present partly as ammonia, partly as protein and other organic forms and a part may even be fully immobilized for the microorganisms as it is incorporated in complex molecules. For the activity of the microorganisms the total C/N ratio is of much less importance than the amounts of C and N actually available at any given moment and the relative proportions of the available carbon and nitrogen. This can be called "available" C/N ratio as distinct from the "total" C/N ratio. It seems likely that normally there will be a certain relationship between the total and "available" C/N ratio. If there is very little nitrogen (wide C/N ratio) there will be little ammonia and if there is a lot of nitrogen (narrow C/N ratio) there will be a high concentration of ammonia in the compost. Because ammonia is very readily available it will greatly influence the "available" C/N ratio and its concentration will be particularly important for the activity of the microflora. Together with the amount of water the concentration of ammonia is of primary ecological importance. This statement must be explained as follows. The amount of water, directly important for the microflora, defines together with the structure of the compost pile the amount of air in the pile and the ventilation of the pile. The oxygen pressure and the total nitrogen content are important for the amount of ammonia that will be set free by the microorganisms. This influences the "available" C/N ratio. So water, oxygen, carbon dioxide and free ammonia ultimately define the activity in the pile. This complex has also been studied by Laborde et al. (1972a, b,) and Tschierpe and Sinden (1962). The production of ammonia increases the pH, while the carbon dioxide produced by the developing microflora in turn neutralizes the pH to some extent. Allison and Kneebone (1962) have already studied the influence of compost pH on mushroom production, but the dependence of the pH on the ammonia content was not mentioned. High temperatures in the pile caused by the microflora growing under optimum conditions have a beneficial effect on the ventilation of the pile and therefore on the oxygen supply of the microorganisms. This influences ammonification and in this way several factors are dependent on each other and influence each other. It is very difficult indeed to describe what is exactly going on in a compost pile. I have paid a lot of attention to the influence of the primary ecological factors water and ammonia, because it is likely that these factors play a deciding role in the composting process and will greatly determine the nature of the microflora and what the quality of the compost will be. In soil microbiology (Parkinson and Waid, 1960; Gray and Parkinson, 1968) the kind of species present is not always important but rather the function of a physiological group as a whole. Within such a group with a special function the kind of species can vary. In this paper primarily the influence of some ecological factors on mushroom production has been studied. It is likely that differences in the composition of the microflora could have been found depending on the treatment of the composts, but we did not study it. Two composts with quite a different microflora could produce the same yield, whereas two composts with the same microflora could give different yields. This is so, because bacteria, actinomycetes and fungi can in part have the same physiological behaviour (e.g., cellulolytic activity) whereas the same microorganisms can react differently under different (e.g., aerobic or anaerobic) conditions. In my opinion mushroom yield depends more on the nature of the ecological factors (e.g., water and ammonia) than on the species of microorganisms developing in the compost under definite conditions The ecological factors will determine the composition and the ultimate result of the activity of the microflora as a whole If the influence of the ecological factors is known it could be significant to study the composition of the compost microflora under several conditions For this work these conditions would have to be well defined In this paper chicken manure and urea are added to fresh horse manure in various quantities to find the optimum amount to be added to the compost To get an idea about the "available" C/N ratio,ammonia was determined in most of the composts In previous work (Gerrits, 1970) it has already been shown that several organic N-sources can be used in the compost and interchanged without adverse effects In this paper this will be proved by one more example The results will be discussed and compared with simdar work on synthetic compost published recently (Gerrits, 1974).
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