SOILS AND FERTILIZERS 



water which accumulates near the sources of large 

 rivers is also a necessity to agriculture. 



The three ways by which crops are deprived of water 

 are, (i) percolation, (2) evaporation, and (3) transpira- 

 tion. With proper methods of cultivation losses by per- 

 colation and evaporation may be controlled, and losses 

 by transpiration may be reduced. 



INFLUENCE OF CULTIVATION UPON THE WATER 

 SUPPLY OF CROPS 



27. Capillarity influenced by Cultivation. The capil- 

 larity and moisture content of soils can be influenced by 



different methods of 

 cultivation, as rolling 

 and subsoiling, deep 

 plowing, and shallow 

 surface cultivation. 

 The treatment which 

 a soil should receive 



FIG. 15. Soil with Surface Cultivation. 



in order to insure the best water supply for crops must 

 vary with the rainfall, the nature of the soil, and the 

 crop to be produced. It frequently happens that the 

 annual rainfall is sufficient to produce good crops, but it 

 is too unevenly distributed, and hence is not all utilized 

 to the best advantage. Losses of water occur through 

 surface drainage, percolation, and excessive evaporation, 

 but if it were properly stored in the subsoil and conserved 

 by cultivation, these losses would be prevented and there 

 would be sufficient for crop production. 



