Are farmers managing crop water use and runoff by striving to improve agronomic production?

Farmers are striving to improve agronomic production by adopting various agronomic practices including crop rotation and reduced tillage. In dry and cold regions, such as the Canadian Prairies, measures of crop residue management are adopted additionally to conserve soil moisture. Although both crop and residue management practices are mainly used for increasing crop yield, they and the resulting changes in crop growth can affect one or more components of the water cycle. This paper reviews the effects of crop type, quantity of crops and crop residues, tillage, and stubble management practices on crop water use (termed including evaporation, transpiration and interception), snow trapping, water infiltration, and runoff. In particular, the review attempts to reveal the impacts of crop and residue management on runoff. It shows that crop and residue management have high potential to affect the hydrological cycle and runoff. Rainfall runoff can potentially be reduced by using crops that intercept and use more water, which can be achieved by choosing appropriate crop types, increasing above-ground biomass, or increasing coverage on the soil surface. The potential reduction of rainfall runoff coincides with the farmers efforts of increasing crop productivity. However, it should be noted that although high stubble and reduced tillage for maintaining good residue cover have agronomic benefits in helping conserve soil moisture and improve soil health, they increase the potential of snowmelt runoff. The review points to the need of future research to assess the agronomic and environmental trade-offs of crop residue management, the linkage between crop water use and runoff, and the impacts of crop and residue manage on runoff across various temporal and spatial scales.