REPOKT OF THE SECEETARY OE AGRICULTURE. LXIX 



rich in plant food as the prairie soils of the Middle West, these light 

 truck soils could not economical!}^ be made to produce as large corn 

 crops as the prairie soils. The difference in the agricultural value of 

 these different types appears to depend not so much upon the chemical 

 composition as upon the physical properties of the soils, and especially 

 upon their relation to moisture. In other words, the chemical char- 

 acteristics of the soil influence the Afield of crops, while the physical 

 characteristics have generall}' the greater importance in determining 

 the kind of crop adapted to the soil. 



This work will require much further investigation before these 

 statements can be definitely proved, but the amount and character 

 of the evidence so far obtained is such that these ideas may be taken 

 safely as working hypotheses. The}^ are now serving us in this 

 capacity in suggesting and giving direction to studies which are con- 

 fidently believed to have far-reaching importance for agricultural 

 methods and practice, studies which in all probability could not have 

 been conceived or planned without the investigations which have just 

 been brieflv outlined. The results of the work indicate, as might be 

 expected, that the composition of the soil moisture is largely influ- 

 enced both by the cultivation and by the cropping of the soil, and 

 appear to show in what way and to what extent cultivation can be 

 depended upon to change these important characteristics. 



The results of the last year's work also seem to indicate the very 

 superficial nature of the droughts which so seriously affect crops in the 

 Eastern and Middle Western States. It has been frequently observed 

 that in a time of drought, when the surface soil becomes desiccated 

 and the plants are suffering, the subsoil at a depth of 1 or 2 feet con- 

 tains but little less than the average amount of moisture, and it has 

 frequently been observed that the crops are much more shallow rooted 

 than they are in the far West. This has been variously ascribed to 

 the uniform texture of the soils and subsoils in arid regions, and to 

 other reasons, but the true explanation seems to be that with our fre- 

 quent and excessive rains in the spring and early part of the growing 

 season, the crops find sufficient moisture near the surface and develop 

 a superficial root system. When the drought comes and the surface 

 soil loses its moisture, the crop suffers because it is not provided with 

 a deeper root S3\stem. In the far West, where spring and summer 

 rains are rare, the crop is planted upon a soil which is always uniformly 

 moist to a considerable depth, and with no subsequent rains the plant 

 develops a deeper root system, which enables it to survive long periods 

 of drought that would seriously affect it if it was subjected to frequent 

 showers during the early period of its growth. It is a familiar fact 

 that a lawn which once is watered during a dry season will have to be 

 frequently watered or the grass will suffer oftentimes more than if it 

 had not been watered at all. The first watering induces a superficial 



