Manures and Fertilizers 129 



by the fertilizer when either the drill or the broadcast 

 method of sowing is used. Scientific experiments show 

 that roots multiply mostly in the soil where the supply 

 of plant-food is most abundant.^ The surface mulch 

 of dry soil keeps the lower parts both moist and cool. 

 Later the heavy tops shade the ground with the same 

 result. This cool lower soil, although itself too dry for 

 roots to grow in, is a marked advantage in hot seasons in 

 preventing degeneration of the potato as well as in increas- 

 ing yield. 2 



This method of applying fertilizers has produced very 

 striking results in dry seasons. In periods of extreme 

 drought the tops showed but little injury from tip-burn and 

 grew continuously. The writer thinks that this success 

 is due to the greater moisture supply made available to 

 the plants by the wide and deep distribution of the root 

 system. This enables the plants to find and utilize the 

 water in a larger volume of soil at the time when the 

 plants need it most. When the roots are encouraged 

 to develop near the surface by broadcasting the fertilizer 

 and working it in shallowly, the drying of the upper soil 

 layer deprives the plants of the use of much of their root 

 system, and may leave them in poorer shape to with- 

 stand hard conditions than if the roots had been forced to 

 spread out and down earlier to find plant-food.^ In the 

 corn-belt, dry weather in June is recognized as a favorable 

 factor for the future success of the corn crop because it 

 forces the plants to root deeply, while a wet June would 

 result in shallow rooting which would be certain to suffer 

 later in the summer. 



1 Storer, " Agriculture." Vol. 1, pp. 297-300. 



" Neb. Agr. Expt. Sta. Bui. 146 ; and Colo. Agr. Expt. Sta. Bui. 216. 

 ' Bureau of Soils. Bui. 22, p. 52. 

 K 



