38 
BULLETIN 157, U. S. DEPARTMENT OF AGRICULTURE. 
The data presented in Table XVI are not wholly dependable, prin- 
cipally because winterkilling so reduced the yields in some years 
that their comparative value was almost wholly lost. The volunteer 
crops on the continuously cropped plat and the plat cropped two 
years hi three were less affected by winterkilling than the sown 
crops, for the reason that they made more growth in the fall. As a 
result, uncontrollable factors, such as thin stands, weeds, etc., 
caused wide variations in the results, which did not indicate the 
true value of the methods employed. 
The continuously cropped plat has not failed completely, however, 
in any year, even in the very dry years 1910 and 1911. In 1911, 
when there was very little winterkilling and good growing conditions 
prevailed, the continuously cropped plat and that cropped two years 
24 
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Fig. 20. — Graphs comparing the average percentage of moisture in each of the upper 10 feet of soil at 
the beginning of each season, as found on the alternately cropped and continuously cropped plats 
at the Nephi substation, 1909 to 1912, inclusive. 
in three fell far below the others in yield. Under favorable condi- 
tions, it appears that the plats that have been fallow one or two 
years will give the best results. So much depends upon the time 
of planting, winterkilling, etc., however, that continuous cropping 
sometimes appears to be profitable, owing to the survival of volun- 
teer grain. 
The severe winterkilling in some years completely offsets the 
advantage of some plats in high soil-moisture content. This is well 
illustrated by figure 20, from which it will be seen that in 1909 the 
difference in moisture content of the continuously cropped plat and 
the alternately cropped plat was greatly in favor of the latter at the 
beginning of the season, yet, because of a better stand, due to the 
volunteer grain, the continuously cropped plat yielded nearly seven 
times as much as the other, as is shown in Table XVI. In 1910 
the differences, though less marked, were much the same as those of 
