FIELD CROPS 413 



of soil washing. The water itself is likely to be needed during some 

 portion of the summer. By loosening the subsoil and covering the 

 surface with a growth of vegetation, the soil can be made so absorbent 

 that the water will penetrate the ground and be held in reserve to 

 sustain the growing plants during times of drought. It would seem 

 that after a period of heavy rainfall, during which 8 or 10 inches of 

 water fell within a month, the soil and subsoil of all fields would be 

 alike saturated, but such is not the case. The condition of the sur- 

 face soil has much to do in determining how much of the rainfall 

 will be absorbed. The condition of the subsoil is also important. If 

 its moisture has been exhausted by lack of cultivation and injudicious 

 cropping, it will absorb water more slowly than when it is already 

 moist. Thus it is that the subsoil of some fields remains dry to a 

 depth of several feet during a season of heavy rains, while that of 

 other fields absorbs water in sufficient abundance to sustain crops dur- 

 ing periods of drought. To readily absorb the water that falls during 

 times of heavy rains the surface soil must be loose and porous, so as 

 to take up the water rapidly before it has time to accumulate, and 

 hold it thus until by capillary attraction it is drawn to the subsoil. 



Some very fine clay subsoils are so compact that they turn water 

 almost as effectually as a slate roof. Such subsoils should be rendered 

 permeable, and the most effective and cheapest way to accomplish 

 this is by growing deep-rooted plants, such as clovers, alfalfa, meli- 

 jotus, etc. The roots of these plants penetrate the subsoil and, decay- 

 ing, leave numerous ducts through which water from the surface soil 

 will pass to greater depths. That this is exactly what occurs is proved 

 by comparisons of plats of ground on which such plants have been 

 crown with adjacent plats on which they have not been grown. The 

 former plats are tillable soon after heavy rains, because the water 

 has found its way into the subsoil, while the latter plats remain 

 muddy on the surface. 



Some subsoils are the reverse of those just referred to ; instead of 

 being too compact they are too open. A subsoil of coarse gravel may 

 allow the water to pass through too readily, thus washing out and 

 draining away the fertility. Such subsoils are not compact enough 

 to supply the surface soil with moisture by capillary attraction. Soils 

 of this nature are greatly benefited by the plowing under of vegetable 

 matter, which, besides adding greatly to the soil fertility, checks the 

 rapid leaching through the subsoil and enables it to retain moisture 

 better during dry weather. The application of vegetable matter im- 

 proves the fertility and physical condition of almost all soils, regard- 

 less of whether the subsoil is compact or porous. 



Retention of Soil Moisture. The amount of moisture needed to 

 produce a crop is much greater than would be imagined. In the case 

 of corn it is sufficient to cover the field with water to a depth of from 

 10 to 15 inches. About three-fifths of this quantity, or from 6 to 9 

 inches of water, is absorbed by the roots and exhaled by the foliage 

 of the growing crop. More corn crops are cut short by an insufficient 

 quantity of available soil moisture tnan by any other cause. This is 

 well demonstrated by the fact that fields situated by rivers or lakes 



