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<br />(., <br /> <br />~ <br /> <br />218 . <br /> <br />. REPORT 01" SECRETARY'. ,'. <br /> <br />doubt about the importance of rB:in duril)g these months,the correla- . <br />tion of yield with July and August rainfall is not as close as it is <br />when effective rainfall up to July lis considered. In the 32 normal <br />crop years given in the Table, 16 show yields over 24 bushels per' <br />acre; averaging 32.5 bushels. 'In this group are found only threo <br />years which had less than the average' ef:Bective rainfall up to July 1, <br />but 8 years'. are found which have less than the average July and <br />August rainfall. The other 16 years average 16.9 bushels per acre.' <br />In this group is found only one year with effective rainfall up to <br />July 1 greater than the average, but 5 years are found with July <br />and August rainfall greater than the average. <br /> <br />Omitting the three exceptional years, 1907, 1913, and 1918, com <br />has averaged 24.7 bushels on 10.81 inches of effective rain to July' 1- <br />The highest yield group shows an average of 39.7 bushels of corn <br />with 19.56 inches of effective rainfall to July 1, arid the lowest yield <br />group an average of 13.8 bushels of corn with 5.69 inches of effectlv.. <br />rainfall to July 1. <br /> <br />During the 32 crop yc~,:s, there are 11 years when the yield of <br />corn has been above 30 bushels per acre, averaging 35.4; bushels; <br />ten years with yields between 20 and 30 bushels, averaging 23.8 <br />busb,els; and 11 yea~s with yields below 20 bushels, averaging 14.7 <br />bushels per acre. The effective rainfall up to July 1 for these \three <br />groups was 16.54 inches, 9.51 and 6.26 inches respectively. The effect". <br />i~ July and August rainfall is 6.47, 4..76, and 4.08 inches respectively. <br /> <br />Considering the 32 crop years the .yield is very close to 2 bushels <br />of corn for 1 inch of effective water before July 1. Projecting <br />the cun'e of average yiields and effective rainfall in Figure 7 would <br />indicate that 12 inches of water added to the average supply will <br />increase the yield of cdrn 20 bushels per acre over the present average. <br /> <br />Inadequacy of the Rainfall for Wheat Production. <br /> <br />The yield of wheat in the last 20 years in' Adams, Kearney, <br />and Phelps Counties has ,...aried from 25.2 bushels per acre in Adams <br />County in 1906, to 5.0 bushels per acre in Phelps County in 1923. For <br />corn, the variation in yields was simply and conclusively shown to be <br />correlated with effective rainfall. . .In the case of wheat correlation of <br />the yield with effective rainfall during the spring and preceding fall <br />is much more complex than for corn, and cannot be sho\VIl on a <br />graph similar to Figure 7. 'Two seasons must be taken into con- <br />sideration in the case of wheat. First, the fall during which the <br />seed bed is being prepared, the seed is being sown and early <br />growth is being established. With the hazards of this season should <br />also be included tne hazards 'of drought. and wind blowing, 'up to <br />the beginning of the growing season about April 1. Second, the spt"ing, <br />including April and May. If the fall season be' unusually dry, the <br /> <br />:"~ <br />