Terminating Cover Crops
As planting season is partially delayed in some areas due to wet weather, farmers are wondering when and how to terminate their cover crops. If soils are wet, a growing cover crop helps dry out soil through evapotranspiration. Crop water use, also known as evapotranspiration (ET), represents soil evaporation and the water used by a crop for growth (transpiration). Transpiration is the water transpired or lost to the atmosphere from small openings on the leaf surfaces. Evaporation is the water evaporated or lost from the wet soil and plant surfaces. When a crop reaches full cover, approximately 95 percent of ET is due to transpiration and evaporation from the crop canopy at full sunlight. About 97-99% of water absorbed by plant roots is lost to transpiration. Most plants have a total transpiration of 440 to 2,200 pounds of water per pound of plant growth. Cool season grasses like rye have a higher transpiration rate than warm season grasses like corn. When cereal rye is at its peak sp