BUREAU OF SOILS. 615 



A study of the effect of beat on soil organic matter, such as it would 

 undergo in the process of sterilization by steam, a subject which has 

 been considered in the past almost wholly from the biological view- 

 point, has led to some highly interesting results. It has been shown 

 that during the process of sterilization some very deep-seated altera- 

 tions are produced in tlie f)rganic matter of the soil, as was shown by 

 the actual isolation of the constituents before and after heating, thus 

 presenting in the heated soil, as it were, an entirely different culture 

 medium for bacteria and other microorganisms which would subse- 

 quently develop. Such heated soils, moreover, in spite of the fact 

 that more nutrients are made available, in past researches have often 

 been shown to be harmful in their first effects toward higher plants. 

 In the soils under study by the bureau the same phenomenon was 

 noticed and the cause traced to the production in the heated soil of a 

 compound inimical to plant development. The compound generated 

 b}' the heat was isolated and identified as the poisonous dihydroxy- 

 stearic acid previously reported from this laboratory as a constituent 

 in many infertile soils. 



Besides the work of identifying the chemical units already men- 

 tioned, a further investigation has dealt with the nature of the black 

 organic particles in soils. This investigation disclosed the fact that 

 nearly all soils contain black particles from the size of a pea to the 

 smallest subdivisions of soil material, which consist of highly car- 

 bonaceous matter, some of which was identified as coal, charcoal, lig- 

 nite, and intermediate material, which in apj^earance and properties 

 suggests such substances as pitchcoal, albert ite, wurtzilite, etc. 



As the result of these researches the viewpoint of agricultural 

 investigators is undergoing a decided change from the old established 

 viewpoint of the purely mineral requirement theo"y. The greatest 

 value, however, of these researches to agriculture lies in their appli- 

 cation to specific soil problems, such as soil exhaustion by continuous 

 cropping and difficulties in orchards or with other specific crops, as 

 well as to the naturally unproductive soil types. Several unproduc- 

 tive soils and specific problems have already been studied, the causes 

 of unproductivity determined, and remedies devised. 



The importance of these investigations can not be overestimated. 

 They are showing us that soils are suborganic entities, with func- 

 tional activities somewhat analogous to those of animals; that soils 

 digest organic material as do animals; and that according as the 

 material breaks down into simpler bodies along one line, with certain 

 by-products, the functional activities of the soil are suitable for the 

 normal growth of certain plants, or in other lines, with other by- 

 products, they are abnormal and unsuited to the functional require- 

 ments of the plant, and. furthermore, that these functional activities 

 of any soil may be controlled by methods of tillage, rotation of crops, 

 and fertilizers. 



SOIL-WATER INVESTIGATIONS. 



The investigations of the subsoil water supply have been continued 

 and the well census, begun the previous year, completed. A publica- 

 tion incorporating th.e results of the investigation has been j^repared 

 and is in course of publication. The outcome of the work is the 

 accumulation of ^vcU tlata that indicate the level of subsoil water in 



