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DEPARTMENT .OF PUBLIC WORKS .205 \ I , i f evaporation is high and where a light shower that merely moistens the surface inch or two of soil is quickly lost thru evaporation. . Such light showers have very little importance so far as the plant being able to utilize them is concerned. They are beneficial in that they. tend to hold down the temperature of the soil and make the atmosphere more humid and consequently reduce the direct transpiration from lhe crops: It is probable, however, that during the warm summer months when the surface of the soil gets very hot that there is little if any feeding roots in the upper surface of the soil. Consequently if a rain is to be highly beneficial it must be sufficient in amount to penetrate several inches into the soil. On the whole it is rains of a half inch or greater that make up most of the effective rainfall. Heavy down- pours of rain, however, are apt to puddle and clog the surface and re- sult in a considerable loss thru runoff. In this particular district where the soil is quite level, there should be a little loss thru runofi. In so far as the character of the rainfall is concerned it is much the same thruout the entire area. In Figure 3is shown the char- acter and distribution of the precipitation at Holdrege, Nebraska. This is based on the entire 20 years' under study. The chart also shows the summer ~nd winter distribution. During the winter months,-October to' March _ inclusive, the rainfail is. rather evenly divided in the various sizes.. The' winter rainfall is never as useful as the' summer rainfaIl because a great deal -of it may come when the ground is' frozen and consequently does not get into the soil, or it may fall as snow and be blown off of the land so as to give very uneven distribution. At Holdrege' 78.6 per cent of the preci- pitation comes during the six summer months and during that period 13.6 inches of the total 23.35 inches, falls in rains' of over half an inch. Frequency of Drought Periods. One of the peculiarities. of the rainfall of the Great Plains area," where this project lies, is ~the fre- quent occurrence of more or less prolonged dry periods, duri~g..which little or no rain falls. As above mentioned, these periods of dro'- are the greatest handicap. to successful crop'production. ..9ujte fre- quently such periods are terminated. by a succession of heavy rains, which 'makes the average of the rainfall appear favorable, whereas the individual seasons may have been disastrous because of - one or more prolonged dry spells. The periods during' which crops' are most affected by shortage of moisture may be described as follows: 1. April 1 to May 15. - During this period are apt to occur high winds which drift the loose dry soil and uproot small. grain crops, and which are often responsible for reduced yields even tho the remain- der . of the growing. setlson may. be favorable. The gennination _of spring sown small grains. may be more or less. seriously affected by .-.-1 t t , ,