Surface residues and no-tillage reduce soil water evaporation

The Issue

Improving water use efficiency is increasingly important as California agriculture confronts water shortages. Changing tillage and crop residue practices could help. In regions of the world where no-tillage systems are common -– such as Brazil, Argentina, Paraguay, Canada, Western Australia, the Dakotas, and Nebraska -– generating and preserving residues are an indispensable part of management and sustainable production. Residues reduce erosion, provide carbon and nitrogen to soil organisms, and reduce soil water evaporation, along with other advantages and drawbacks. The water conservation value of crop residues and conservation tillage has not been evaluated in the warm, Mediterranean climate of California. This study measured the effects of residues and no-tillage on soil water evaporation in California conditions.

What Has ANR Done?

Increasing the amount of water that is transpired by a crop relative to the amount that is evaporated by the soil, by reducing tillage or maintaining surface residues, may improve the water use efficiency in California crop production systems. In two field studies of standard tillage versus no-tillage operations, following wheat silage harvest prior to corn seeding, more water (approx. 1 inch) was retained in the surface foot of soil under no-till than in tilled soil. In three studies comparing residue effects on soil water evaporation, bare soil retained less water (approx. 0.4 to 0.6 inches) than under residues following 6-7 days of overhead sprinkler irrigation. Assuming a seasonal crop evapotranspiration (ET) of 30 inches, coupling no-tillage with high residue preserving practices could reduce soil evaporative losses in summer by about 4 inches (10.2 cm), or 13 percent. Before converting California cropping systems to no-tillage, residue-preserving production techniques, some practical factors must be considered.

The Payoff

No-tillage plus high-residue preservation practices reduce soil water evaporation in summer

Improving the water use efficiency of crop production systems by reducing the amount of water that is evaporated by the soil is an important management goal for California agriculture. Transitioning tillage and residue management systems commonly used in California to high residue, no-tillage practices may partially accomplish this goal based on studies in Nebraska and Texas. Surface residues have been shown to modify the partitioning of seasonal ET by decreasing total soil water evaporation, increasing total crop transpiration, and increasing water use efficiency by 37 percent for strip-till grown cotton in wheat residue versus cotton under conventional plow tillage. However, a number of practical factors will need to be addressed before wholesale cropping system transformation to no-tillage, residue-preserving production occurs in California. In addition, more research is needed on water balance and crop productivity under actual no-till and high-residue field conditions.

Contact

Supporting Unit:

Department of Plant Sciences and Department of Land, Air and Water Resources
 
Jeff Mitchell (jpmitchell@ucdavis.edu)
Wes Wallender (wwwallender@ucdavis.edu)
Dan Munk (dsmunk@ucanr.edu)
Will Horwath (wrhorwath@ucdavis.edu)