420 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



a laboratory in that section is considered essential in order that the 

 department may be in a position to cooperate effectively with the 

 grain trade in meeting these conditions. 



BIOPHYSICAL INVESTIGATIONS. 



The biophysical investigations, which form a continuation and 

 extension of the work formerly conducted by the physical labora- 

 tory, have been carried on during the past year under the direction 

 of Dr. L. J. Briggs. 



This work is largely cooperative in character, and at the present 

 time is devoted mainly to problems arising in connection with the 

 growth of crops in arid and semiarid regions. Extensive experi- 

 ments are being conducted at Akron, Colo., and at other points in the 

 Great Plains, to determine the amount of water required by different 

 dry-land crops for the production of a pound of dry matter. The 

 experiments are conducted in large pots containing over 200 pounds 

 of soil, the surface of the soil l:)eing protected in such a way that 

 water can be lost only through the leaves of the crop. About 300 

 pots have been used in the Akron investigations, supplemented by 

 over 200 pots at other points in the Great Plains, and at Washington. 

 The results show that plants differ greatly in their water require- 

 ments, millet and sorghum being the most economical in the use of 

 water, while alfalfa requires four times as much water as millet 

 for the production of the same amount of dry matter. A bulletin 

 upon this subject is now ready for publication. 



Suitable apparatus is also supplied to the dry-land and irrigation 

 experiment farms for the purpose of providing a comprehensive 

 record of the climatic and other environmental factors influencing 

 the growth of crops. It is indispensable that such records should 

 include measurements of evaporation, the moisture content of soil, 

 and the rate of growth of the crops, in addition to the usual data of 

 rainfall, temperature, humidity, and wind velocity. Several new 

 stations have been equipped during the year, most of the apparatus 

 necessary having been made in the instrument shop of the laboratory. 



A cooperative study has been made of the native vegetation in 

 the Tooele Valley, Utah, on the south side of Great Salt Lake, to de- 

 termine to what extent the native growth can be used to indicate the 

 capabilities of the land for dry farming. This valley affords an 

 exceptional opportunity for this work, the vegetation often appear- 

 ing in well-defined zones, occupied in some areas by single species 

 only. It was found that the distribution of native plants was de- 

 termined by both the alkali content and the soil moisture supply, 

 and that certain plants are reliable indicators of the soil conditions 

 in this region. The results of this investigation are now being pre- 

 pared for publication. 



The investigation of the effect of electrical stimulation upon the 

 growth of plants has been continued, but the weather was too damp 

 to allow satisfactory insulation at the time the plants were growing 

 most rapidly, and the field experiments were inconclusive. The 

 greenhouse experiments, in which the insulated network over the 

 plants was kept charged throughout the nigl>r, showed in the case 

 of radishes a depressing effect upon the growth as the result of the 



