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'-, . 214 HEPORT OF SJ<::CRETARY average effective rain. At Holdrege 48 dry periods have occurred, averaging 48 days in leng!;h and with an average' of '.47 inches of effective rain. The distribution of the;S'e dry p'eriods is shown' graphically in Figures 4, 5, and 6. These figures also show graphically the yield of corn and wheat during the period of twenty years. The seriousness of a dry period of over 40 days will depend upon the moisture con- ditions of the soil at the beginning of the drought and the time when the dry periods begin and end. However, when such dry periods come, as frequently they do in central Nebraska, it is probable that some crop damage resutts from them almost every year.. It was to over- come the seriousness of such periods of drought by having water stored in the soil, which would maintain the crop thru the dry period,. that this irrigation project was conceived. " . , Inadequacy of Rainfall for C,orn Production. That period of drought, coming between Julyl'and 'August 21 may ruin a corn crop. is well known to farmers i'n' Central Nebraska: That such a disaster ma~' be avoided or at least' mitigated to con- siderable . extent by adequate moisture up'10 July 1 may not be so well understood. Statistical studies of corn yields and rainfall in Phelps and Adams Counties during the last 20 years offer convincing proof that abundant rain' and con~quently moisture in the subsoil on July i tends to offsQt 'dry spells of weather after that date. The evidence indicates that if the subsoil is well filled with water on' July 1 as would be the case if rainfall during the' pl1eceding spring and fall' had been heavy, a fairly good crop of corn can be expected. Only extreme drought or other abnormal conditions would bring about serious damage. . :,. In the last 20 years the yields of corn, as r.eported in . Nebraska crop estimates, has varied from 42.3. and 38.3 bushels per acre in . Phelps and Adams County, respecth-ely, in 1905 0;5 and 3.6 bushels per acre in 1913. This wide variation in yield n(l's' been dlllC almost entirely. to rainfall. In attempting to correlate the yield of corn with rainfall, only the rains of over .50 inch faIling during the preceding fall months,- namely, SeptJember, October, and November, and the spring months,- April, May and June, have:.'been considered. Much of the corn in'the section is planted in corn land, and the preceding crop is using water up to September 1. Where corn is planted in stubble land, the weeds of the, 'fall before generally Ui'e moisture up to September 1 or later. Since the. attempt at correlation is to show only the value of stored water, rainfall during July and August of the crop year should' not be included. .' '. Table 5 shows the correlation between the effective i'ainfalI . '( .1 q 1 . .~...:,~ ..'