484 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



these researches have led to the discovery of organic soil constituents 

 deciJcdl}; beneficial to growing crops. It has been demonstrated that 

 one, a nitrogenous constituent, creatinine, exists in soils, exists m 

 manures, and exists in many plants and seeds, whereas it was hitherto 

 recognized only in connection with products of animal origin; that 

 it is beneficial to crops, and that it is able to replace nitrates in aiding 

 plant growth. 



The facts demonstrated bv these investigations are of funda- 

 mental significance in soil fertility. The recognition of these directly 

 beneficial soil constituents is no less important than the recognition 

 that harmful soil constituents exist. The creatinine appears to be 

 as favorable as soil nitrates to croj) production, and even to be able 

 to replace the latter in such a manner that the amount of nitrate 

 required is less in its presence, while plant growth is increased. 

 The amount in soils is, moreover, comparable with the amount of 

 nitrates as usually found in agricultural soils. Creatinine is, how- 

 ever, only one of a long list of nitrogenous and phosphorus carry- 

 ing organic compounds of the soil, and the remarks here made will 

 probably find application to many other of these soil constituents. 



This extended study of soil organic matter or humus, about which 

 so little definite information existed in chemical and agricultural 

 literature, was undertaken as the result of the discovery of a harm- 

 ful property in extracts from unproductive soils. This led to the 

 discovery of harmful compounds, which fact showed the great im- 

 portance of more accurate knowledge concerning that most impor- 

 tant and yet least understood soil constituent — the organic matter or 

 humus of soils. Starting without methods and with no definite con- 

 stituent ever isolated from soil, the work has steadily progressed 

 until to-day over 25 organic compounds have been identified and 

 classified. The list of the compounds so far isolated varies from 

 simple compounds, containing only carbon and hj^drogen, to complex 

 compounds, containing carbon, hydrogen, ox3'gen, nitrogen, and 

 phosphorus. They are compounds which exist as such in living 

 plants or arise from the decay or decomposition of the proteins, fats, 

 nucleic acids, carbohydrates, and other plant and animal substances, 

 as the result of purely chemical oxidations and reductions and 

 through the intervention of molds, bacteria, protozoa, and other bio- 

 logical influences in soils. According to the factors operative in the 

 decay of this plant and animal debris in soil, the course of change is 

 different, resulting under one set of conditions in the formation of 

 the abnormal and harmful constituents alluded to above and under 

 other conditions in the formation of normal or beneficial organic 

 constituents of soils. 



It is an essential part of this survey of the organic matter in soils 

 to Isarn the properties of the individual constituents and their effect 

 on the life within the soil and on growing crops, and this phase of the 

 subject, as well as the study of the influence of the fertilizers upon 

 these constituents has been vigorously pushed during the past year. 



The new point of view which has been brought to bear on the 

 problems connected with the fertility of the soils has opened up 

 avenues of profitable investigation and already forecasted results of 

 great economic importance. These investigations have been made on 

 soil from various parts of the United States, comprising a number of 



