Tillage and Crop Residue Affect Irrigation Requirements

With more residue cover, less solar energy reaches the soil surface and air movement is reduced near the soil surface, resulting in a reduction of evaporation of water from the soil beneath the residue cover. Light, frequent rains or irrigations are less effective than heavy, infrequent ones, because, with every wetting event, evaporation takes place from the crop canopy, the residue, and the soil.

In addition to reducing evaporation, higher residue levels and long-term no-till increase infiltration and reduce runoff, thus directing more water to where the crop can use it. Similarly, in the winter, more standing residue means that more snow stays where it falls, thus storing more water in the soil once the snow melts.