USE OF WATER BY SPRING WHEAT ON" GREAT PLAINS. 



29 



Comparison of Figure 10 with Figure 9 shows some interesting 

 facts. In the first place, the quantity of water calculated as neces- 

 sary before a yield above zero would be produced is lower at North 

 Platte than at Edgeley in spite of the fact that it is located much 

 farther south. The reason for this is not known, unless it is because 

 of the shallowness of the Edgeley soil, which makes even a short 

 drought seriously reduce the yield. 



The point most in evidence is this : Each bushel of yield at Edgeley 

 requires 0.2 inch of water above the minimum, and each bushel yield 

 at North Platte requires 0.4 inch of water above the minimum. A 

 greater mass of data to work from would undoubtedly change the 



_£ 



cl ^ ^ ^ 



. ^^1 B 



^—-Q — 



20 



/s 

 /s 



/4 

 8 



e 



4 



2 4-68/0/2/^/6/8 20 22 24 26 28 30 32 3* 36 



£CS//£IS 



Fl ™ I 0- — diagram showing the yield of wheat and use of water on plat A at North 

 M=f22 040 10 years< The liDe is drawn from tne linear-regression equation 



slope of these lines somewhat, but it is apparent that the quantity of 

 water necessary to produce each successive bushel of yield is much 

 higher at North Platte than at Edgeley. 



The linear-regression formula has been used in computing yields 

 at North Platte. Table 6 gives for plat A at North Platte the water 

 use in inches, the actual yield, and the yield computed by the linear- 

 regression equation. 



Table Q— Actual and computed yields of wheat per acre on plat A at North 

 Platte, Nebr., in the nine years stated. 



[The quantity of water used during the growing season as stated in the table forms the 

 oasis of the computed yield as calculated by the linear-regression equation M=6.22 + 





Water 

 used. 



Yieia. 



Year. 



Water 

 used. 



Yield. 



Year. 



Actual. 



Com- 

 puted. 



Actual. 



Com- 

 puted. 



1908 



Inches. 

 14.70 

 16.80 

 7.75 

 9.06 

 9.17 



Bushels. 

 22.7 

 23.0 



6.8 

 12.8 



6.0 



Bushels. 

 21.2 

 26.5 

 3.8 

 7.1 

 7.4 



1915 



Inches. 

 16.46 

 9.98 

 9.70 

 14.22 



Bushels. 

 22.7 

 17.2 

 4.2 

 15.5 



Bushels. 



25.6 

 9.4 

 8.7 



20.0 



1909 



1916 



1910 



1917 



1912.... 



1919 



1914... 









