USE OF THE RAINFALL 237 



resorted to for the purpose of enabling the rains to enter 

 the soil. Fall plowing is practised as early as convenient, 

 and the soil is frequently left in the rough throughout 

 the winter. The fall, whiter and spring rains are quickly 

 absorbed by such land and stored to considerable depths, 

 as already explained in Chapter III. Where the chief 

 precipitation comes in late spring and summer, it is 

 sufficient to plow in early spring and to keep the soil loose 

 during the time of precipitation by tilling after each rain. 



147. Cultivation. The purpose, effect and method of 

 cultivation have been discussed hi Chapter IV. It is the 

 best known method for retaining the natural precipita- 

 tion in the soil. It is just as important that the soil be 

 carefully cultivated after a rain as after an irrigation. In 

 the spring the land should be properly harrowed and culti- 

 vated, so that the moisture gathered during the winter 

 may not evaporate. 



148. Proportion of rainfall conserved. In the inter- 

 mountain country, where the precipitation comes in winter 

 or early spring, it has been found that, by fall plowing 

 and spring cultivation, from 60 to 90 per cent of the pre- 

 cipitation between harvest and spring is found stored in 

 the soil in the spring. In the region where the rainfall 

 comes largely in spring and summer it has been found that 

 it is possible to store in the soil during the summer sea- 

 son from 40 to 60 per cent of all the moisture that falls 

 at that time. Water so stored in the soil is of great value 

 in producing crops; especially valuable is the water 

 stored in the soil during winter, for it has been hi very 

 intimate contact with the soil particles and is heavily 

 charged with plant-foods. 



149. Relation of irrigation- and dry-farming. There 

 is no opposition between dry-farming and irrigation- 



