8 BULLETIN 1304, IT. S. DEPARTMENT OF AGRICULTURE 
them free from weeds throughout the season. The C plats in the 
milo and kafir series are fall-listed and are coordinate with the F 
plats of the other series, instead of the C plats with which their letters 
coincide. The listing, however, is later. The E plats are early deep 
fall-plowed at the same time as the B plats and in every other way 
are identical with those plats in their treatment, except that after 
intervals of two years they are sub-soiled for two years in succession. 
The subsoiling operation consists of running a common single-nosed 
subsoiler in the bottom of each alternate plowed furrow. The sub- 
soiler does not turn out any of the subsoil to be mixed and incorpo- 
rated with the surface soil, but merely loosens it to a depth of 8 inches 
below the bottom of the furrow slice. In the years of subsoiling these 
plats are loosened to a depth of 15 or 16 inches below the surface. 
The F plats are early listed at the time plats B and E are early plowed. 
The ridges are worked level before seeding and the plats given good 
seed-bed preparation. The corn and spring-wheat series are extended 
to include plats designated by the letter G. In the corn series this 
plat is spring-listed and planted in contrast to plat F, which is fall- 
listed. In the spring-wheat series it is deep and late fall-plowed in 
contrast to plat B, which is deep and early plowed. The average 
date of deep late plowing plat G in the spring-wheat series is 
November 9. By deep plowing is meant a uniform plowing depth 
of 7 inches. This applies to all previous or subsequent allusions to 
deep plowing. 
The following different annual crops appear in the stated number 
of plats each year on the experimental field : Spring wheat in 14 rota- 
tions and 6 methods of treatment in the continuous-cropping series, 
a total of 20 plats; winter wheat in 12 rotations and 5 methods of 
treatment in the continuous-cropping series, a total of 17 plats; oats 
in 26 rotations and 5 methods of treatment in the continuous-cropping 
series, a total of 31 plats; barley in 4 rotations and 5 methods of 
treatment in the continuous-cropping series, a total of 9 plats; corn 
in 21 rotations and 6 methods of treatment in the continuous-cropping 
series, a total of 27 plats; kafir in 2 rotations and 3 methods of treat- 
ment in the continuous-cropping series, a total of 5 plats; milo from 
1908 to 1921, inclusive, in 2 rotations and 3 methods of treatment in 
the continuous-cropping series, a total of 5 plats; and sorgo in 1 rota- 
tion from 1908 to 1921, inclusive, and in 1922 and 1923 in 3 rotations 
and 3 methods of continuous cropping. 
Since 1909, when cultural practices became established, these 
experiments have run continuously and now total 15 years. In that 
period the following aggregate number of plat-year records of the 
harvested annual crops have accumulated for study: Spring wheat, 
300; winter wheat, 255; oats, 465; barley, 135; corn, 405; kafir, 75; 
milo, 71; and sorgo, 19. In addition to the annual crops, alfalfa and 
bromegrass each occupy 3 years of separate 6-year rotations. Be- 
sides the harvested crops already enumerated, winter rye in 6 rota- 
tions, peas in 6 rotations, and sweet clover in 2 rotations are plowed 
under for green manure. Fallow plats appear in 4 rotations, besides 
appearing once in each of the 5 series of continuous-cropping plats. 
The varieties grown in these investigations were Beloturka (durum) 
spring wheat, Kharkof winter wheat, Kherson oats, Coast or Cali- 
fornia Feed barley, Swadley dent corn, Dawn or Blackhull kafir, Dwarf 
