142 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



plies of good seed. The crop of hempseed last fall, estimated at 

 about 45,000 bushels, is the largest produced in the United States 

 since 1859. A very large proportion of it was from improved strains 

 developed by this bureau in the hempseed selection plats at Arling- 

 ton and Yarrow Farms. Small packets of this seed have been sent 

 each spring during the last four years to hempseed growers in 

 Kentucky, and 1 pound, grown under favorable conditions, may 

 yield enough seed to sow 20 acres broadcast for fiber. The supe- 

 riority of these strains is recognized, and they are used for planting 

 nearly all fields of seed hemp. 



EGYPTIAN COTTON IN ARIZONA. 



The very high prices obtained for the 1916 crop of Arizona Egyp- 

 tian cotton resulted in the planting of nearly 40,000 acres in 1917, 

 of which 7,000 acres were of the new Pima variety and the re- 

 mainder of the older Yuma A'ariety. The strength of the demand 

 for this type of cotton is indicated by the fact that a single corpora- 

 tion manufacturing automobile tires has stated its annual require- 

 ment for this type of cotton to be 65,000 bales, which it is endeavor- 

 ing to meet by stimulating production in Arizona. 



The efforts of this bureau, cooperating with the growers' associa- 

 tions, to maintain the purity and uniformity of the Pima variety 

 are proving highly successful, as was shown by the very small per- 

 centage of plants removed in roguing the fields selected for seed 

 increase. 



CHESTNUTS. 



Some very promising varieties of chestnuts have been developed, 

 which show considerable promise as nut-producing trees because of 

 their fruitfulness and precocity of bearing as well as their evident 

 measure of resistance to the chestnut bark disease. In this collection 

 of trees there are about 1,500 representing both native and Asiatic 

 varieties, about 50 per cent of which are hybrids. Observations on 

 the hybrid chinkapins which were developed some years ago have 

 been continued. The results are considered especially promising. 



AGRONOMIC AND HORTICULTURAL INVESTIGATIONS. 



METHODS OF GROWING COTTON UNDER IRRIGATION. 



The cultural problems encountered in growing cotton under irri- 

 gation are numerous. Means of securing a good stand, methods of 

 spacing, and the manner of irrigating the crop are some of the 

 features that are being studied. The new single-stalk system of 

 culture has contributed to the establishment of the Egyptian cotton 

 industry in the Salt River, Gila, and Yuma Valleys of Arizona 

 and can be used effectively in the production of all cotton under 

 irrigation. The new system not only induces earlier fruiting and 

 tends to insure larger crops but greatly facilitates the picking of the 

 cotton. 



The single-stalk system of controlling the branching habits of 

 the cotton plants has made possible, also, another special method of 



