4 BULLETIN 1315. U. S. DEPARTMENT OF AGBICTJI/TUBE 
wheat and of corn, each on a standard method of preparation, are 
also shown in this figure. The years 1914. 1919. and 1921 each 
received practically the same seasonal precipitation, but differed 
considerably in the yields of corn and spring wheat. The annual 
precipitation was less in 1914 and in 1921 than in 1919. The order 
of yields for these three years places 1921 first. 1914 second, and 
1919 third. In 1914 and 1921 the yields of corn were higher than 
those of wheat, but in 1919 they were nearly equal. In 1915 the 
corn yield was nothing and the wheat yield high, but in 1916 and in 
1922 these records were reversed. The only year when both the 
corn and wheat yields were excessively low was 1919. During this 
same year the yield of Kursk millet was 2.141 pounds of forage. The 
only yield of millet lower than this in the nine years from 1913 to 
1921. inclusive, was 1.770 pounds of hay in 1914. The 9-year aver- 
age yield was 3.310 pounds of hay per acre. It is apparent from these 
results that different crops respond differently to the same seasonal 
precipitation. The factors which influence this response are: (1) 
The distribution of the precipitation: (2) differences in cultural 
methods: 3' differences in the dates of maturity of crops; and (4) 
differences in the resistance of crops to drought, disease, and storm. 
Each of these factors is of sufficient importance to require the careful 
consideration of anyone undertaking an agricultural pursuit in the 
region. 
EXPERIMENTAL METHODS 
The unit of experimentation is the tenth-acre plat. The plats are 
2 by 8 rods. They are separated on the ends by 20-foot roadways 
and on the sides by 5-foot alleys. The roadways and alleys are 
cultivated and kept clean of vegetation except such as grows in late 
summer. The usual farm machinery is used for all operations, and 
the held conditions incident to the cultural methods under trial are 
maintained as closely as possible. 
The staple crops — spring wheat, winter wheat, oats, barley, flax, 
and corn — are grown in continuous-cropping series by several 
methods of cultivation, including alternation with fallow. They 
are also grown in rotations involving various combinations of succes- 
sion and of cultivation. The cultural methods to which these 
crops have been subjected are spring plowing, fall plowing, sub- 
soiling, listing, disking, fallowing, and green manuring. Barnyard 
manure has been used on a limited number of plats. Alfalfa and 
bromegrass each appear in 6-year rotations. 
Durum spring wheat was used in the rotation experiments. From 
1913 to 1918, inclusive, the variety was Beloturka. C. I. Xo. 1520: 
in 1919. 1920, and 1921 Arnautka, C. I. Xo. 1493: and in 1922 and 
1923. Acme. C. I. Xo. 5284. Turkey winter wheat was used to and 
including 1918. The variety of winter wheat grown in 1919. 1920. 
and 1921 was Kharkof. and in 1922 and 1923 it was Kanred. The 
oat was Swedish Select except in 1922 and 1923. when Ligowa. a 
variety of the same type, was grown. The variety of barley was 
Coast, C. I. Xo. 690^ (California Feed), except in 1923. when a 
change was made to White Smyrna. C. I. Xo. 65S. The flax was the 
common seed type. The variety of corn used is considered in 
presenting the results with that crop. 
