LOSS OF RAINFALL 97 



spring wheat were placed in the moist surface soil, 

 and 1 inch of dry soil added to the surface to pre- 

 vent evaporation. No more water was added; the 

 air of the greenhouse was kept as dry as possible. 

 The wheat developed normally. The first ear was 

 ripe in 132 days after planting and the last in 143 

 days. The three cylinders of soil from semiarid 

 western Nebraska produced 37.8 grams of straw 

 and 29 ears, containing 415 kernels weighing 11.188 

 grams. The three cylinders of soil from humid 

 eastern Nebraska produced only 11.2 grams of straw 

 and 13 ears containing 114 kernels, weighing 3 

 grams. This experiment shows conclusively that 

 rains are not needed during the growing season, if 

 the soil is well filled with moisture at seedtime, 

 to bring crops to maturity. 



What becomes of the rainfall ? 



The water that falls on the land is disposed of in 

 three ways: First, under ordinary conditions, a 

 large portion runs off without entering the soil; 

 secondly, a portion enters the soil, but remains near 

 the surface, and is rapidly evaporated back into the 

 air; and, thirdly, a portion enters the lower soil 

 layers, from which it is removed at later periods by 

 several distinct processes. The run-off is usually 

 large and is a serious loss, especially in dry-farming 

 regions, where the absence of luxuriant vegetation. 



