30 SOILS AND FERTILIZERS 



secure 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 is too 

 unevenly distributed, and hence is not all utilized to 

 the best advantage. It is possible, to a great extent, 

 to vary the cultivation so as to conserve the moisture 

 of the soil and meet the requirements of crops. 



28. Shallow Surface Cultivation. When shallow 

 surface cultivation is practiced, the capillary spaces 



Fig. 13. Soil with surface cultivation. 



near the surface are destroyed and the direct connec- 

 tion of the subsoil water with the surface is broken, 

 a layer of finely pulverized earth covers the surface, 

 and the soil particles have been disturbed so there 

 is not that close contact which enables the water to 

 pass from particle to particle. When evaporation takes 

 place there is a movement of the subsoil water to the 

 surface, but if the surface is covered with a layer of 

 fine earth of different texture, the subsoil water can- 

 not readily pass through such a medium, and evapora- 

 tion is checked. Hence shallow surface cultivation 

 conserves the soil moisture. 



The means by which surface cultivation is accom- 



