206 EXPERIMENT STATION RECORD. 



the provisions of the act, will be awaited with keen interest by all 

 workers in agricultural science. They will be inclined to concur in 

 the sentiment of British scientists, as expressed in a recent issue of 

 Nature: " The occasion is a critical one for agricultural science. The 

 amount of money is considerable and much will be expected in return 

 for it; if those engaged in agricultural research can justify its expen- 

 diture they will be rendering good service not only to agriculture 

 but to science in general." 



The soil is made up of organic and inorganic or mineral constitu- 

 ents. Except in the case of peat soils and those of like nature the 

 mineral constituents make up by far the greater proportion of the 

 soil mass. Cameron found the average proportion of organic matter 

 in surface soils (to a depth of 8 inches) of the United States to be 

 2.06 per cent and in subsoils 0.83 j^er cent, or 28 tons per acre to a 

 depth of 8 inches and 50 tons to a depth of 2 feet. 



Notwithstanding the relatively small percentage of organic matter 

 in ordinary soils, the fertility and productiveness of the soil depends 

 to such a large extent uj^on its organic constituents that no soil is 

 considered normal without a certain proportion of organic matter. 

 Although this fact is generally recognized, the organic constituents 

 of the soil have not been so thoroughly studied as the inorganic or 

 mineral constituents, and as a result exact knowledge of the nature 

 and function of these constituents is very deficient. Schreiner says : 

 " Every soil investigator, whether it be the chemist, bacteriologist, or 

 physicist studying some special problem, or the agronomist dealing 

 with the general relation of soils to crops, sooner or later encounters 

 difficulties that have their origin in the lack of knowledge of the 

 chemical composition of the organic matter of the soil." 



A great deal has been written about the nature and importance of 

 the organic matter of the soil, particularly the so-called humus, and 

 many views have been held as to its relation to crop production, these 

 views changing from time to time, but there has really been very 

 little accurate, undisputed scientific data upon which to base these 

 views. Throughout the century or more of controversy on the sub- 

 ject, however, humus has always been recognized as a most important 

 factor in soil fertility. In fact, the older investigators of the subject 

 were disposed to give an exaggerated importance to humus as a 

 direct and essential element of plant food, measuring the fertility of 

 the soil entirely by the amount of humus present. Until within recent 

 years a modification of Mulder's view, that humus and the larger 

 part of the organic matter of soils is made up of humus acids having 

 the same general properties in different soils, was generally accepted. 



More recent investigation, however, has shown that this view is 

 untenable and that humus is a very complex substance made up of a 



