M 



THE AGKICULTUKAL NEWS. 



FKEia-AKV 8, iyi9. 



in well cultivated lauds containing; relatively little 

 ■humus, bacteria play a very important part, and occur 

 in great numbers, and the moulds are of minor impor- 

 tance; while the upper layers of soil in forests, rich in 

 humus as they are, contain a large number of moulds. 

 In rainy seasons also the siirtace growth of moulds is 

 greatly favoured: otherwise they live and produce 

 spores below the surface among the vegetable residues 

 and the living plant roots. It has been demonstrated 

 that not only are moulds present in the soil, but that 

 they actually live there, and produce mycelia, which 

 necessitates their taking an active part in the different 

 biological transformations of the soil. 



Thus to be able to interpret the part played by 

 these organisms in the soil, they must be studied as 

 living organisms, which by their metabolic processes 

 help in the various transformations of both organic 

 and inorganic soil i;onstituents, ^nd in this way inriu- 

 ence soil fertility. 



The ijuestion of nitrogen fixation by moulds 

 seems to be that, with the exception of some rather 

 rare organisms, typical soil moulds do not play any 

 direct part in the nitrogen enrichment of soils. Nor 

 has the formation of nitrite or nitrate ever been 

 ■demonstrated for any of the mouliis, so that these 

 important activities must be eliminated from the field 

 of mould action. 



On the other hand, the moulds are found to play a 

 very important part in the disintegration of organic 

 matter in the soil, particularly in the first sr.ages of 

 decay, which is termed ammonification. Whatever 

 may be the process of formation of complex proteins 

 by moulds, it is certain that ammonia is left in the 

 medium as a waste product. If avaikble carbohydrates 

 are present, only small i|uantities of ammonia will be 

 liberated by the action of bacteria and moulds, but iu 

 the absence of available carbohydrates there is a large 

 amount of nitrogen left, in the medium by their action. 

 If the ammonia is regarded as an indication of the 

 amnunt of organic matter decompv')8ed by a living organ- 

 ism, some of the monlils commonly occurring in the soil 

 are found to po9s<!ss greater powers of decomposing 

 organic matter than are po.sse.ssed by bacteria. 'I'he 

 action of the moulds cm the nitrogenous organic 

 matter in the soil may be .said to consist in the 

 mineralization of that material, with the produc- 

 tion ol amir)onia and the building up of fungus 

 proteins. The ammonia is used by the higher plants 

 :is such, or is oxidi/ed Viy nitrifying bacteria into 

 nitrates, and so Used- by plants, or is absorbed again by 

 the micro- organisms of the soils. 



The moulds also play an active p.irt in the decom- 

 position of celliilose and o'her cirb >a compounds in 

 the soils. This is of great importance, since both green 

 and animal manures, and all vegetable residues need 

 to be decomposed befofethe minerals and nitrogen eom- 

 p)unds can be brought to a condition in which they 

 can eiuher be taken up directly by the higher plants, or 

 in which they cin undergo other transformations 

 due to the acuion of other groups of moulds or 

 bacteria. It is stated that nearly all the simple and 

 complex organic carbon compounds in the soil can 

 be attacked by some group or other of moulds, 

 which thus play an important pirt in soil fertility. 

 The moulds attack the carbohydrates very readily, per- 

 haps even more readily than the bacteria, and they 

 cause rapid "lecomposition of these compounds. 

 Although more information is necessary, it appears 

 certain now, that future theories of soil fertility will 

 have to be constructed, not only from the point of view 

 of nitrogenous manures and fertilizers and nitrogen 

 • C(jntent of the soil, but also by taking into consideration 

 the nature and amount of carbon compounds ailded to it. 



It nnist be kept in mind, however, that lower 

 plant organisms like motxlds, when present in the soil, 

 compete with the higher plants in utilizing nitrogenous 

 compounds for their own growth. Thus the soil 

 moulds may produce an unfavourable effect upon 

 soil fertility. Athough this cannot be denied, two 

 factors may be mentioned as in some degree coun- 

 terbalancing the possible injury to higher plants. 

 First, an excess of ammoiiium salts or nitrates in 

 the soil tends to large losses by leaching, especially 

 imderwet climatic- conditions; the utilization therefore, 

 of some of these sales by the soil moulds may serve 

 usefully for the conservation of some of this nitrogen 

 in the soil, which would otherwise be lo3t. Secondly, 

 the life processes of the moulds tend to the liberation 

 f>f ammonia, and to the restoring again to the soil of the 

 nitrogen assimilated by them in an available form. 

 Thus moulds from this point of view, may act in the 

 soil as storing agents for soluble nitrogen ouipounds; 

 and the possible injury caused by them in competing 

 with the higher plants for the available nitrogen may 

 be more than compeusated for by their ability to store 

 the nitrogen, and make it afterwards slowly available 

 tor the plants. 



Inlormalioii up to the present leajs to the belief 

 that the mould flora is mi)re active in acid than in 

 neutral or alkaline soil, although it does not preclude 

 the fact that moulds are developed also in fhe latter 

 type of soil. It is possible that some of the soil moulds 



