How To Increase The Water-holding Capacity Of Soils

Fortunately for the farmer he can do much to increase the amount of film water that some soils can hold, and thereby increase their productiveness. The farmer who irrigates should be interested in the subject as much as the farmer who depends upon natural rainfall to supply his crops with water; it is tedious and expensive to irrigate frequently, and he should know how to increase the capacity of his soil to hold water so that fewer irrigations will be needed. Under-drainage is the most efficient means of improving a soil in which the water table is always so close to the surface that the soil is too wet for farm crops ; or which is very wet in winter and very dry in summer. Deep plowing, harrowing, cultivating and other tillage operations also do much to deepen the soil and enlarge the reservoir, because the more a soil is pulverised the more water it will hold. The addition of humus to a soil in the form of farm manure, muck or a green manure, has a very marked influence on its ability to hold water. Furthermore, if the surface of the soil is softened, rains sink into it better. Fall plowing will leave the soil loose so that it will absorb the winter rains : if the surface is hard and compact, much of the water runs off. All of these operations are so fundamental to successful farming that each one is discussed at length in subsequent chapters. Influence of Forests on Water Supply. — The influence of forests upon the water supply should not be overlooked. When forests near streams are removed, the soil of the adjoining farm land is made dryer, and there is increased danger of floods. The large body of humus beneath forest trees holds an immense amount of water, like a sponge — nearly twice as much as its own weight when dry. In times of drought, this water is given off gradually to adjoining dryer land. Moreover, the air near large forests contains more moisture than the air of cleared areas because the trees give off large quantities of water through their leaves: hence farm soils in deforested areas lose water more rapidly, because the air above them is dryer. There are thousands of acres of land in this country which have been cleared of timber to use for farming, but which are nearly valueless for that purpose and should revert to forest; to say nothing of the wholesale destruction of forests for timber alone. Policy, as well as sentiment, should induce every man to [leave as much of his farm in woodland as is practicable.