Soils 



41 



21. Control of soil- water by cropping methods. As may 

 be inferred from the foregoing statements, the control of water 

 is an important factor in keeping soil in the best condition for 

 profitable crop production. The farmer can increase water for 

 crops by reducing the loss due to run-off and to percolation, 

 by reducing the quantity evaporated from the surface, and by 

 improving the structure of the soil, thus making it possible for 

 the soil to retain more water. 



Reducing run-off losses. When land is rather impervious 

 to water and in regions of heavy rainfall, the amount of water 

 lost by run-off from the surface may be excessive, if proper 



FIG. 16. A badly washed field. 



precautions are not taken to reduce it. The loss is occasioned 

 largely by the water not entering the soil. One remedy is 

 proper cultivation. If the surface of the soil is hard and com- 

 pact and all tillage operations are shallow, there is less oppor- 

 tunity for water to enter than if the surface is loose and the soil 

 has been cultivated to a good depth. 



On hilly land the quantity of water retained can be influenced 

 by laying the furrows to encircle the hill, thus making it possible 

 for the water to be retained on the surface until much of it 

 has time to soak into the soil. This is known as contour 

 plowing. In sections in which the soil washes readily, terraces, 

 which are low ridges of earth encircling the slope at nearly 

 a perfect level, are made on the slopes. Along these terraces 



