Rainfalls not Equally Productive 105 



the soil, such as takes place in Kansas, tends strongly 

 to hold the roots near to the surface, where with scanty 

 mulches they are certain to suffer severely whenever a 

 period of ten days without rain occurs ; and if, under 

 these conditions, the plant is able to send new roots 

 more deeply into the soil, they can find there but a 

 scanty supply of moisture, because there have been no 

 winter rains sufficient to produce percolation. Then, 

 again, after such a ten -day drought, with the surface 

 roots now become inactive through a dying off of the 

 absorbing root -hairs, when the next rain does fall, 

 unless it is a very heavy one, the major part of it will 

 be lost by evaporation from the soil, in the case of 

 crops like wheat, oats, rye and barley, long before the 

 plants are able to put themselves in position to take 

 full advantage of it. 



In California and eastern Washington, the case is 

 radically different. There the water gets well into the 

 soil before the crop is put upon the ground. Moisture 

 enough is present to produce germination, and the 

 roots develop at first near the surface, when there is 

 ample moisture present ; but later, under the rainless 

 conditions, it is quite likely that they advance more 

 and more deeply into the ground as the moisture in 

 the upper layers of the soil becomes too scanty, and 

 thus day by day the effectiveness of the soil -mulch is 

 increased, while the roots have only to advance so far 

 as is needful to allow capillarity to bring them the 

 water they need from the store which the soil has re- 

 tained. With these physical principles and conditions 

 set down as foot -lights to illuminate our problem, and 



