Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: The three ways in which crops are deprived of water are by (i) percolation, (2) evaporation, and (3) transpiration. With proper methods of cultivation, losses by percolation and evaporation may be controlled, and losses by transpiration may be reduced. INFLUENCE OF CULTIVATION UPON THE WATER SUPPLY OF CROPS 25. Capillarity Influenced by Cultivation.—The capillarity of the soil is subject to change with different methods of cultivation, as rolling and subsoiling, deep plowing and shallow surface cultivation. The method of cultivation which a soil should receive in order to 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. It is possible, to a great extent, to vary the cultivation to meet the water requirements of crops. 26. Shallow Surface Cultivation. — When shallow surface cultivation is practiced, the capillary spaces near the surface are destroyed and the direct connection of the subsoil water with the surface is broken. When the soil particles have been disturbed and a layer of finely pulverized earth covers the surface, 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 thesurface, but if the surface is covered with a layer of fine earth, the subsoil water cannot readily pass through such a medium, and evaporation is checked. Hence shallow surface cultivation conserves the soil moisture. The means by which surface cultivation is accomplished must, of necessity, vary with the nature of the Fig. 13. With surface cultivation. soil. If a harrow is used the pulveri...