226 ANNUAL EEPORTS OF DEPAETMENT OF AGRICULTURE. 



CHEMICAL INVESTIGATIONS. 



At no time in the history of the bureau has there been so* great 

 a demand made on the laboratories devoted to the chemical investi- 

 gation of soils for the examination of samples as during the past 

 year. This has been due, no doubt, to the increased interest in the 

 stimulation of greater crop production brought about by war con- 

 ditions. This increase of routine work has come both from indi- 

 vidual farmers who have sought advice regarding liming, fertilizing, 

 or cultural treatment of soils, in which case work was undertaken 

 only when it was thought some laboratory examination would be of 

 value to farmers generally, and from other bureaus of the depart- 

 ment and other departments of the Government where the same 

 interest in greater crop production has brought about an increased 

 demand for work of this nature. 



Such time as could be spared from routine work has been devoted 

 to investigations chiefly along two lines — the inorganic composition 

 of soils and the liming of soils. In connection with the former, work 

 has been continued on a study of the composition of the water ex- 

 tract of soils and important and interesting results obtained, and 

 in cooperation with the soil survey progress has been made toward 

 determining the composition of samples of virgin soils of more 

 important soil types. 



In the investigation of the liming of soils results have been ob- 

 tained that throw light on the character of soil acidity and will tend 

 to make it possible for the practice of liming to be carried on in a 

 more intelligent manner. 



SOIL PHYSICS 



Owing to unusual conditions due to the war a large part of the 

 time and force of the Physical Division has been employed in co- 

 operating with the Division of Fertilizer Resources. Assistance has 

 been furnished especially in solving the physical and mechanical 

 problems involved in the preparation of synthetic ainmonia by the 

 Haber process and in the oxidation of ammonia in solution by 

 electrolytic means. 



Investigations on the excessive erosion of soils have been continued 

 and the physical properties of soils subject to erosion determined. 

 The movement of water in soils has been investigated and a com- 

 parison made of the methods for determining the critical moisture 

 content. The relation of absorbed moisture to the critical moisture 

 content has been studied. The effect of temperature changes on the 

 physical condition of the soil is being studied. The colloidal condi- 

 tion of clay soils has been investigated to determine the cause of 

 high degree of stickiness in such soils. Systematic study of the 

 physical properties of important soil types has been imdertaken. 



In addition to these lines of work the usual mechanical analyses 

 of soil samples collected by the Soil Survey have been made, and an 

 unusually large number of samples for other bureaus have been 

 analyzed during the year. One machinist also has been continuously 

 employed in the construction of unusual pieces of apparatus and in 

 the repair of instruments for the bureau. 



