502 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



There was also sent to the printer a joint publication prepared in 

 cooperation with the Bureau of Entomology and designed to assist 

 orchardmen who wish to make their own lime-sulphur spray. 



Cooperative work with the same bureau in connection with the de- 

 velopment of cotton-boll-weevil control was continued. The work 

 of the year consisted largely of testing commercial dusting machines 

 submitted to the laboratory, in advising with manufacturers in 

 regard to machine design and construction, and in disseminating 

 information and assisting prospective purchasers in the selection of 

 suitable equipment. The interest shown by manufacturers who are 

 considering the production of dusting machinery and of planters 

 confronted with the boll-weevil problem was highly gratifying. A 

 new development in the work is the use of airplanes equipped with 

 dusting machines. Such experimental work as has been done indi- 

 cates the desirability of further investigations and experiment with 

 such equipment. 



The replacement to a certain extent of horses and mules by me- 

 chanical power has become quite general on the farm and has created a 

 demand from farmers considering the purchase of tractors and trucks 

 for unprejudiced information. To meet the demand studies have 

 been necessary in various sections of the country. These have been 

 undertaken independently and in cooperation with the Office of Farm 

 Management and Farm Economics and the Bureau of Animal In- 

 dustry. As a result Farmers' Bulletin No. 1278, Tractors on South- 

 ern Farms, and Department Bulletin No. 997, The Cost and Utili- 

 zation of Power on Farms Where Tractors are Owned, have been 

 published and a Farmers' Bulletin, Corn Belt Farmers Who Own 

 Motor Trucks, is with the printer. 



In order to bring together in a comprehensive and related form 

 the information obtained in the various farm power investigations 

 that have been made in the Corn Belt, a series of bulletins was pre- 

 pared bearing the following titles: Choosing the Tractor; Cost of 

 Using the Tractor; Shall I Buy a Tractor; Changes Effected by the 

 Tractor; What Tractors and Horses Do. The manuscripts which 

 deal with Corn Belt conditions and which were prepared in cooper- 

 ation with the Office of Farm Management aiid Farm Economics, 

 were submitted for publication. 



Department Circular 212, published during the year, is a report 

 of the manufacture and sale of farm equipment in 1920. It was the 

 intention to continue the compilation of such reports year by year, 

 but the work was transferred to the Bureau of the Census, which 

 will compile the information for the ensuing year. 



DISTRIBUTION OF SURPLUS WAR EXPLOSIVES. 



In accordance with an act of Congress (Public, No. 7, 66th Cong., 

 H. R. 5227) some 12,000,000 pounds of picric acid, a surplus war 

 explosive, was turned over by the War Department to the Depart- 

 ment of Agriculture for distribution to farmers as a means of encour- 

 aging land clearing. This picric acid is furnished to the farmer at the 

 actual contract cost of drying, cartridging, packing, and shipping 

 (6 cents per pound) , plus a charge of 1 cent per pound to reimburse 

 the State cooperating agency, usually the agricultural college, for 



