24 



BULLETIN 157, U. S. DEPARTMENT OF AGRICULTURE. 



Table IX. — Annual and average percentages of moisture in each of the first 6 feet of soil 

 at different dates of seeding at the Nephi substation, for the years 1908 to 1912, inclu- 

 sive — Continued . 



Date of seeding. 



Depth of 

 sampling. 



19081 



1909 



1910 



1911 



1912 



Average. 



Oct. 1 



1 

 2 

 3 

 4 

 5 

 6 



20.00 

 19.40 

 15.55 

 11.27 

 10.77 

 12.72 



15.60 



18.90 

 16.00 

 17.90 

 16.70 

 17.05 



12.88 

 16.43 

 16.58 

 16.78 

 18.38 

 16.33 



13.47 



16.07 

 14.98 

 15.24 

 14.34 

 14.23 



12.55 

 17.00 

 14.49 

 13.17 

 13.57 

 13.37 



14.90 

 17.56 

 15.52 





14.87 

 14.75 

 14.74 





14.95 



17.02 



16.23 



14.72 



14.03 



15.39 





f 1 



2 

 3 

 4 

 5 

 I 6 





Oct. 15 



16.90 

 18.60 

 15.35 

 14.10 

 11.08 

 10.92 



15.35 

 17.75 

 16.55 

 16.05 

 16.65 

 17.75 



14.61 

 16.80 

 16.65 

 16.33 

 16.28 

 18.00 



12.29 

 14.98 

 14.63 

 13.57 

 11.65 

 13.14 



17.87 

 18.59 

 17.40 

 15.92 

 13.75 

 15.45 



15.40 

 17.34 

 16.12 





15.19 

 13.94 

 15.05 





14.49 



16.68 



16.44 



13.44 



16.50 



15.51 





f 1 



2 

 3 

 4 

 5 

 I 6 





Nov. 1 



18.55 

 20.52 

 19.72 

 13.90 

 11.15 

 10.37 



13.95 

 17.35 

 16.20 

 13.95 

 14.15 

 14.60 



17.85 

 18.78 

 18.30 

 17.63 

 17.05 

 16.65 



14.68 

 18.02 

 14.60 

 11.25 

 8.97 

 15.49 



(2) 



f 16. 26 

 18.67 

 17.21 





14.18 

 12.83 

 14.23 





15.70 



15.02 



17.69 



13.84 





15.56 











1 One plat only. In each of the other years the figures given are the average of two plats. 



2 Stormy weather prevented the sampling and seeding of these plats. 



It will be noticed in Table IX that there was no great difference in 

 the average moisture content of the plats. The surface foot, usually 

 very dry in the first few inches, varied in moisture content to some 

 extent, owing partly to rainfall, but even in this foot the variation is 

 within the limits of experimental error. Moisture in the first foot of 

 soil is of chief importance at seeding time, because it is here that the 

 plant starts life, and for this reason some relation between the moisture 

 content of the first foot of soil at seeding time and the yield of the 

 crop might be expected. This relation failed to appear, however, in 

 any one year. That it was not apparent in an average for the four 

 years from 1909 to 1912 is shown in figure 14, in which the average 

 moisture content of the first foot of soil on the six different dates of 

 seeding, and the average yields of two varieties of winter wheat seeded 

 on those dates are graphically presented. 



Figure 14 shows an apparent relationship between the moisture 

 content of the first foot of soil and the yields of the plats seeded 

 on the two earlier dates, but for later dates the curves run almost 

 parallel to each other. A discussion of the physical factors influenc- 

 ing the time of seeding will aid in explaining this condition. 



FACTOES INFLUENCING THE TIME OF SEEDLNG. 



On the dry lands of the Great Basin the best time for seeding 

 winter wheat is greatly limited by climatic conditions. The long, 

 dry summers exhaust the moisture of the fallow soil nearly to the 

 depth to which the land is plowed, leaving the surface soil almost 



