36 



DRY FARMING CONGRESS. 



Dry-Land Arboriculture. 



The importance of tree growing in connection with dry-land agricul- 

 ture has not yet been fully realized in the United States. However, the 

 Bureau of Plant Industry has taken up the matter, and drought-resistant 

 trees, valuable for their fruits, timber and as sources of forage in excep- 

 tionally dry years, are being studied. 



A variety of olive, very rich in oil and grown successfully without 

 irrigation under an average rainfall of 9.3 inches, has been found in 

 southern Tunis, and has been introduced into the United States where it 

 is being tested in the arid region from western Texas to southern Cali- 

 fornia. 



Other useful tree crops now under investigation are desert varieties of 

 the peach and plum. These promise to be valuable as stocks on which to 

 graft less hardy varieties and for crossing with the latter. 



In the Mediterranean region and in the drier parts of Asia, drought- 

 resistant varieties of most of our principal orchard trees exist and it is 

 believed that these will be found better adapted to the arid and semi-arid 

 parts of the United States than many of the varieties now grown there. 



In Australia and in northern Africa certain species of trees that are 

 able to grow with very little water are the dependence of stockmen as a 

 source of forage in years so dry that the range grasses fail. It is believed 

 that the introduction of such trees will greatly benefit portions of the 

 western United States where the live stock industry is paramount. They 

 will be valuable not only as a reserve supply for forage but as windbreaks, 

 shade trees and a source of fuel. 



Breeding Crop Plants for Drought-Resistance. 



The Bureau of Plant Industry is experimenting with various forage 

 plants with a view to increasing their ability to grow in comparatively dry 

 soils; the method being the selection of the individual plants that show 

 themselves most resistant to drought. Seed from these selected plants is 

 sown the following spring and the most drought-resistant individuals among 

 the progeny are again selected. This is continued year after year until 

 a distinctly drought-resistant variety is obtained. 



This work has been in progress for two years in co-operation with the 

 South Dakota Experiment Station, at Highmore, South Dakota, and plans 

 are being made to extend it to other stations in the Great Plains area. The 

 most important crop plants being bred for increase of drought-resistance 

 are alfalfa, sorghum, broom corn millet; fox tail millet, smooth brome grass 

 and some of the native wheat grasses. 



Value of Native Growths in Classifying Land. 



The problem of the classification of land with respect to its crop pro- 

 ducing power is a very important one in the arid and semi-arid parts of the 

 country where vast tracts of public land held for sale by private corpora- 

 tions still remain unbroken. Both buyer and seller desire to know what the 

 land is good for, and how many acres of it will be required to support a 



