Soil Water Evaporation and Crop Residues

Crop residues have value when left in the field and also when removed from the field and sold as a commodity. Reducing soil water evaporation (E) is one of the benefits of leaving crop residues in place. E was measured beneath a corn canopy at the soil suface with nearly full coverage by corn stover or standing wheat stubble. E was also measured from a soil surface that was partially covered with corn stover without crop shading. E was measured with mini-lysimeters that were 300 mm in diameter and 140 mm deep. Surface coverage and amount of dry matter of crop residues influenced E. E was reduced nearly 50% compared with bare soil E when corn stover and wheat stubble nearly covered the surface under a corn canopy during the growing season. Partial surface coverage, from 25% to 75%, with corn stover caused small reductions in E compared with bare soil when there was no crop canopy. Full surface coverage reduced energy limited E 50% to 65% compared with E from bare soil with no shading. No-till management, using crop residues to significantly reduce E, required soil surfaces to be nearly covered. Economic benefits of crop residues for E suppression during the growing season can be as much as $365 ha-1.