It tends to keep the soil cold.
It dilutes plant food in the soil.
It interferes with proper tillage.
INDICATIONS OF A NEED OF DRAINAGE
The above-mentioned state of affairs occurs sometimes in fields at the foot of hills, or on sloping uplands which receive spring water or seepage water from higher lands. Some fields are underlaid by a close, compact subsoil which so checks percolation that the surface soil is too wet for tillage operations the greater part of the year. In such cases:
A need of drainage is generally indicated by the presence of more or less free water standing on the surface.
In some lands the surface water does not appear as free water standing on the surface. In such cases:
A need of drainage is indicated by the curling and wilting of the leaves of corn and other crops during dry, hot weather. This curling and wilting is due to the fact that during the early growth of the crop free water stands so high in the soil that the crop roots are confined to a shallow layer of soil. When dry, hot weather comes, the free water recedes, the upper soil dries out, and the roots cannot get sufficient water to supply the demands of transpiration, hence the curling and wilting of the leaves.
If drains are placed in this soil, the free water will be kept at a lower level in the spring and the plant roots will develop deeper in the soil, where there will be constant supply of film water during the dryer and warmer summer weather.
The wiry and spindling growth of grass and grain crops may indicate too much water.