16 DRY FARMING IN THE GREAT BASIN. 



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investigation of these conditions is Avell warranted, not only by any- 

 one studying the subject as a whole, but also by anyone proposing to 

 begin such farming in that region. Some of these conditions, such 

 as the character and annual distribution of the rainfall, are much 

 the same for the whole region, but other conditions, such as the 

 actual amount of the rainfall, are largely influenced by the local 

 topography and therefore vary greatly even within a limited area. 



PRECIPITATION MAINLY IN WINTER. 



In the Great Basin, as in nearl}'- all of that part of the United 

 States lying west of the Kocky Mountains, the larger part of the 

 precipitation occurs during the winter rather than during the sum- 

 mer months. In this respect the climate differs from that of the 

 great semiarid region east of the Rocky Mountains. 



Contrary to the generally accepted opinion, there seems to be good 

 reason for believing tliat more economical use of a limited rainfall 

 is possible when the larger part of it takes place during the winter 

 than Avhen the rains are mostly, confined to the summer months. 

 This is particularly true when the rainfall is too light to produce 

 a crop every year, so that summer fallowing or alternate-year crop- 

 ping is necessary to conserve the scanty supply. 



There are several reasons for this. When the rain comes during 

 the cool weather a much smaller percentage of it is immediatelj' 

 evaporated than in warmer j^eriods, so that more of it soaks into the 

 ground. When rain falls on the hot, dry ground in midsummer it 

 takes at least one-fourth of an inch to wet the surface and establish 

 connection with the moist soil below, while on the heavier soils at 

 least one-half inch is needed to penetrate the dry surface. After 

 the rain has ceased a considerable quantity of water evaporates 

 before the surface is dry enough to cultivate, if cultivation is possi- 

 ble, while with standing grain and similar crops the direct evapora- 

 tion from the soil continues until all moisture within reach of the 

 surface that has not been taken up by the plants meanwhile is lost 

 into the air. 



With a favorable soil — a soil with sufficient fine material to have 

 a high water-holding capacity, yet with enough coarse material to 

 IDcrmit easy penetration of rain water — the best use of a limited 

 rainfall is possible when it occurs during the cooler months, either 

 as snow or as slow rains of one-half an inch or more at a time, so 

 as to give a maximum of penetration and a minimum of run-off and 

 evaporation. This is, of course, not true for all climates nor for all 

 soil types. Where the winters are long and severe, so that the 

 ground is deeply frozen, wintei- precipitation would be largely 

 wasted in surface run-off and by evaporation before the ground 



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