LOSSES OF MOISTURE AND PLANT FOOD BY PERCOLATION. 27 



It is evident, from the foregoing discussion, that cultivation is much 

 in ore effective in decreasing evaporation from some soils than from 

 others, and that those on which it is effective are the sands or loam 

 soils which lose water rapidly by evaporation from the uncultivated soil. 

 The difference,- however, may be due to some other factor operating 

 during wet periods, and not to natural evaporation differences. 



The average evaporation from the clays and loam is much less, even 

 from the uncultivated soils, than it is from the sands and loams. A 

 three-inch cultivation may also be effective on the heavier soils, where 

 a two-inch cultivation has little or no value. 



The gain of water due to the checking of evaporation by a two-inch 

 cultivation of the sands or loams averages 3.52 inches per year. If this 

 saving of moisture occurred during the crop season, and could all be 

 utilized by the crop, it would be sufficient approximately for the fol- 

 lowing production: 



Cotton, pounds lint 280 



Corn, bushels 21 



Wheat, bushels 14 



Oats, bushels 33 



Table No. 9 shows the percolation by quarters from the cultivated 

 and uncultivated soils. Table No. 10 shows the increased quantity of 

 water percolated, due to the cultivation. The table brings out clearly 

 the low percolation during the summer months. Part of the diminished 

 percolation during the winter months may be due to the replacement of 

 water evaporated during the summer. 



These tables again emphasize the necessity of storing water in the 

 soil and subsoil for use during the growing season. They also bring 

 out the very slight effect of the cultivation of the clay group of soils, 

 on the loss of water in percolation pots. 



TABLE NO. 9. 

 Percolation in Inches by Quarters. 



