BUREAU OF PLANT INDUSTRY. 325 



Ikdicator value of natural vegetation. — As a result of three 

 years' field vrork in a portion of the Great Plains area it has been pos- 

 sible to work out detailed correlations between the native growth on 

 different types of land and the capabilities of those types for crop 

 production. It is found that land which is naturally covered with 

 short grass is best adapted to shallow-rooted and early-maturing 

 crops, such as small grains, and that v»'hile such land gives the largest 

 yields in years of heavy and well-distributed rainfall, it is most sub- 

 ject to drought in years when the precipitation is light or confined to 

 the early part of the summer. On the other hand, land covered with 

 a vegetation of the taller and deeper rooted wire grass, or of the still 

 larger bunch grass and species of similar habit, is well adapted to 

 deep-rooted crops and such as require a longer season for maturing. 

 While production on lands of the tall-grass types is relatively smaller 

 in wet years than on short-grass land, it is much surer in dry years. 



The physical reasons for these correlations are that moisture pene- 

 trates deeper and is held longer in wire-grass and bunch-grass types 

 of land than in short-grass land. It was very gratifying to observe 

 during the extreme drought of 1910 that the predictions based upon 

 previous studies of the structure and physiology of the natural vege- 

 tation on these different types of land as to their relative adaptability 

 to different crops and their relative productivity in times of drought 

 have been abundantly fulfilled. This year the best crops were gen- 

 erally grown on the wire-grass and the bunch-grass land, while crop 

 failures have been more numerous on the short-grass land which 

 yielded so well in 1909, the wet year. It is proposed to continue this 

 work in order to ascertain what modifications of these correlations 

 will be necessary in order to make them applicable throughout the 

 Great Plains area. 



PHYSICAL INVESTIGATIONS. 



The work of the Phj^sical Laboratory, under the direction of Dr. 

 L. J. Briggs, Physicist, is largely cooperative in character. During 

 the past year cooperative work has been carried on to a varying ex- 

 tent with about one-half of the offices in the Bureau. 



The principal lines of investigation have had reference to the 

 growtli of crops in dry-land regions, such work having been con- 

 ducted in cooperation with several of the offices of the Bureau. The 

 object has been to determine what method of crop rotation and culti- 

 vation are most efficient in securing penetration of the rainfall and in 

 preventing evaporation. Special attention has also been given to a 

 study of the climatic conditions at each of the dry-land experimental 

 farms of the Bureau to determine the effect on crop production. The 

 subject of evaporation has been given particular attention, since the 

 amount of rainfall required is dependent upon the amount of evapora- 

 tion taking place. Several bulletins have been prepared during the 

 year giving the results of various lines of cooperative work. 



FARM-MANAGEMENT INVESTIGATIONS. 



The Farm-]Management Investigations of the Bureau have con- 

 tinued during the past year under the direction of Prof. W. J. Spill- 

 man, Agriculturist, with few changes in the problems investigated 



