360 SOILS. 



It thus appears that although the nitrogen of the unhumified 

 organic matter constituted about 40% of the total in the origi- 

 nal soil, it would during the entire year have contributed only 

 to an insignificant extent to the available nitrate-supply ; while 

 the fully humified " matiere noire " contributed fourteen times 

 as much. During the ordinary growing-season of four or five 

 months the unhumified organic matter would have yielded 

 practically nothing to the crop. 



Functions of the unhumified Vegetable Matter. The chief 

 utility of the unhumified matter in the soil consists of course 

 in its gradual conversion into true humus, in the course of 

 which it evolves carbonic gas to act on the soil minerals ; while 

 at the same time it helps to render the soil more porous and 

 thus facilitates the action of the aerobic bacteria, for which it 

 serves as food. Hence the addition of vegetable matter to soils 

 not already too " light " is always advantageous, so long as 

 it does not introduce injurious, non-humifiable ingredients, 

 like turpentine in the sawdust of resinous pines. But it is al- 

 ways advisable to first use such matter as litter for stock, in 

 order to better prepare it for the processes of humification, 

 under the influence of ammonical fermentation, such as occurs 

 in the decay of green plants or animal matter. A portion of 

 the ash ingredients also is quickly utilized by solution in the 

 soil-water. 



Matiere Noire the Only Guide. According to these results 

 it is clear that in order to gain any tangible indications with re- 

 spect to crop-bearing, it is the nitrogen in the humus proper, 

 the matiere noire only, that should serve as the basis ; and that 

 as a current source of nitrogen to the plant, the unhumified 

 matter is hardly entitled to more consideration than the " in- 

 soluble silicates." For, the favorable conditions for nitrifica- 

 tion under which the above experiment was conducted, will 

 very rarely be even approached under field conditions. 



What are the Adequate Nitrogen Percentages in the Humus f 

 The nitrification of the matiere noire being, apparently, the 

 main source of plant-nutrition with that element under ordin- 

 ary conditions, the question naturally arises as to what may be 

 considered an adequate nitrogen-content of that substance, so 

 as to permit a full supply of nitrates to the crop. 



