20 BULLETIN 698, U. S. DEPARTMENT OF AGRICULTURE. 



EXPERIMENTAL CONDITIONS. 



In order that the experimental results may be properly inter- 

 preted, descriptions of the methods of obtaining data and of the 

 environing conditions prevailing in each season are given here. 



Methods Employed. 



The size and arrangement of plats, the method and rate of seeding, 

 the date when the crop was sown each year, the rotation of crops 

 on the experimental area, and the methods of obtaining certain data 

 are explained in the following paragraphs. 



SIZE AND ARRANGEMENT OF PLATS. 



The plats used in these experiments were 8 rods long by 2 rods 

 wide, containing a tenth of an acre each. These plats were laid out 

 in blocks of 10. Each block was bordered on all four sides by a road 

 19.2 feet wide. Each plat, therefore, had a road at each end, and 

 the first and tenth plats in each group or block had a road on one 

 side. A guard row usually is placed between the first and tenth 

 plats and the adjacent roads. 



In the experiments with small grains, definite alleys are left 

 between 'plats, to prevent mixing and to facilitate the handling of 

 the crop. Since the grain sorghums are sown in widely spaced rows 

 no alleys were needed for these purposes, and usually none were 

 left. The regular 42-inch space between rows served as an alley. 

 In 1910, however, 5-foot alleys were left between the plats, thus 

 giving the crop thereon the benefit of 9 inches of extra space on each 

 side of the plat. 



Each plat contained 10 rows, 132 feet long and 42 inches apart. 

 Usually each variety occupied 10 rows, or a tenth of an acre. Some- 

 times, however, fewer than 10 rows were sown. In 1914 all varieties 

 were sown on 5-row or twentieth-acre plats. In sowing the varieties 

 the rows were made longer than 132 feet. When the plants were 

 15 to 20 inches (4 to 5 dm.) in height, the ends of the rows were 

 trimmed to the proper limits. 



METHOD AND RATE OF SEEDING. 



A 1-row corn driU, fitted with special sorghum plates, was used for 

 sowing the crop until 1910. Since then a 2-row corn drill, fitted in 

 the same manner, has been used. The plates for sowing milo and 

 durra contain 18 holes, each three-sixteenths of an inch in diameter. 

 For kafir the plates have 16 holes, each five thirtj^-seconds of an inch 

 in diameter, and for kaohang 25 holes the same size as for kafir. The 

 feed was run on high gear, which drops at intervals of 6.4, 7.2, and 

 4.6 inches, respectively, with plates bored as stated above. 



It was the intention to have only one kernel dropped at a time, but 

 in many cases two and sometimes three kernels were dropped because 

 of the thickness of the plates and the varying size of the kernels. 



