8 BREEDING DEOUGHT-RESISTANT FORAGE PLANTS. 



rainfall, like the eastern Uniterl States and western Europe. In 

 recent years the Department of Agriculture has introduced a large 

 number of more or less drought-resistant crop plants from foreign 

 countries where the climatic conditions more nearly resemble those 

 of the Great Plains area. Even with these ])lants, however, prelimi- 

 nary tests show that there is much opportunity for breeding work to 

 improve the quality, increase the yield, and eliminate the less hardy 

 and less drought-resistant individuals. 



Cultivated forage plants are greatly needed in the Great Plains 

 area. Until recently this was essentially a stock-raising territory, 

 and although large parts of it are now being divided up into small 

 farms devoted to grains and other crops, it seems altogether likely 

 that stock raising will continue to be one of the chief industries. In 

 the past the chief dependence of the stock grower has been the 

 "range;" in other words, the native growth of prairie grasses. Only 

 scattered attempts have been made to grow cultivated forage plants, 

 but as the region becomes more and more settled there will be an 

 increasing demand for hay and other stock feeds to supplement the 

 wild-grass pasturage. The growing of forage plants is likely to 

 become one of the most important phases of Great Plains agriculture. 



The chief limiting factor in the production of crops in this region 

 is the lack of sufficient moisture. One means of meeting this defi- 

 ciency is the use of tillage methods tliat will conserve water in the 

 soil, preventing as far as possible loss by evaporation. Another 

 means of attacking the problem is to grow the most drought-resistant 

 varieties that can be obtained. The investigations described in the 

 present bulletin are concerned with developing such varieties by 

 breeding methods. 



The principal factors that enter into drought resistance are prob- 

 ably the ability of the plant to develop a root system that will uti- 

 lize to the utmost a scanty supply of soil moisture and its ability to 

 reduce transpiration, or loss of water, through the leaves and stems 

 when the air is very dry. It is evident that certain species and varie- 

 ties of crop plants are better e({uipped in these respects than others, 

 since they wilt less rapidly when the soil moisture is deficient and 

 when hot, dry winds are blowing. Every farmer on the Great Plains 

 knows that under such conditions the sorgos, kafirs, and milos, for 

 example, will remain fresh and green longer than corn; moreover, 

 within the limits of a single crop species there are great differences 

 in drought resistance, some varieties being superior to others. This 

 has been abundantl}^ l)rove(l in the course of the variety-testing work 

 of the Office of Grain Investigations and of the state experiment sta- 

 tions, which have shown certain varieties of wheat, oats, barley, etc., 

 to be more drought resistant than others. Finally, every close observer 



196 



