28 BULLETIN 1173, U. S. DEPARTMENT OF AGRICULTURE. 
As is shown in Table 14 the average yield for the tenth-acre plats 
plowed in the spring and in the fall for the 12-year period from 1910 
to 1921, inclusive, were practically identical. In the other compari- 
sons between spring plowing and fall plowing the average yields 
were slightly in favor of the fall plowing. The average yield from 
the spring-plowed land in the three experiments for the 6-year 
period from 1916 to 1921, inclusive, was 25.2 bushels and the aver-_ 
age yield from the fall-plowed land during the same period was 25.5 
bushels per acre, a difference of 0.3 bushels per acre in favor of fall 
plowing for summer fallow at Nephi. 
Using these results as a basis of judgment, it might be stated 
that dry farmers in the Great Basin area should plow part of their 
land to be summer fallowed in the fall, and if any is left for spring 
plowing it should be only such an acreage as can be plowed within 
the first few weeks of spring. 
DEPTH-OF-PLOWING EXPERIMENTS. 
Experiments to determine what effect depth of plowing may have 
on the yields of wheat grown after summer fallow were conducted at 
Moro, Lind, and Nephi. At Moro spring wheat was grown on land 
plowed early in April, both 5 and 10 inches deep. At Nephi winter 
wheat was grown on land plowed 5 and 10 inches deep in the fall, 
subsoiled 15 to 18 inches deep, plowed 8 inches deep in the fall and 
3 inches deep in the spring, plowed 3 inches deep in the fall and 8 
inches deep in the spring, and plowed 8 inches deep in both fall and 
spring. At Lind wheat was grown on land plowed 4 and 6 inches 
deep on two dates, September 1 and November 1, and on land 
plowed 4 and 8 inches deep on three dates, March 1, April 1, and 
June 1. 
RESULTS AT MORO. 
In the depth-of-plowing experiments at Moro 40 tenth-acre plats 
were used, 20 being in crop and 20 in fallow each year. Plats 3 and 
8 in each series of 10 are check plats uniformly cultivated, all being 
plowed 8 to 9 inches deep and the fallow kept clean. Table 15 
shows the yields of each plat in these experiments in the years 1912 
and 1914 to 1921, inclusive, no results being available for the year 
1913. Certain of these yields are shown graphically in Figure 16. 
Table 15 shows that there was considerable variation in the average 
yield of the individual check plats in each series. The check plats 
(No. 3) which were located in the west end of each series gave lower 
average yields than the check plats (No. 8) which were located in the 
east end of each series. The average yield of the two check plats in 
the shallow-plowed series was 21.5 bushels, and the average yield of 
the two check plats in the deep-plowed series was 21.6 bushels per 
acre, indicating that the productivity of the soil of the two series 
was practically the same. The average yield, therefore, of the eight 
Bee pees shallow and of the eight plowed deep should be com- 
arable. 
E The 9-year average yield of the eight tenth-acre plats plowed 5 
inches deep (Table 15) was 20.4 bushels per acre, and the average 
yield of the eight plats plowed 10 inches deep in the same period was 
21.3 bushels per acre, an increase of 0.9 bushel in favor of the deep 
plowing. 
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a ety. 
