Quantifying crop water requirements in the Mississippi Delta using an energy balance approach

摘要

Timely quantification of consumptive water use of crops (evapotranspiration, ET) from planting through harvest is a critical input for managing irrigations for optimum crop production. Scheduling irrigations based on ET demands of plants can help reduce both water wastage and scarcity by enhancing water use efficiencies in crop production. We developed a residual energy balance procedure (EB) for rapidly quantifying ET from cropping systems based on measurements of the various components of heat energy balance of a land-crop canopy system was developed from components studied previously in the literature. In the EB, ET (ETe) is expressed as the latent heat flux that was computed as the residual energy from a crop-land surface energy balance equationwhen net radiation and soil heat flux were measured, and sensible heat flux estimated from measurements of plant surface radiative temperature and air temperature, relative humidity, and wind speed at a constant height above the canopy. For a cotton field in Bushland, TX, ETe compared well with ET measured concurrently in a lysimeter. The EB methodology was then used to quantify ET for irrigated corn in Stoneville. The cumulative seasonal values of alfalfa reference crop ET (ETr) compared better than the grass reference crop ET (ET0) with ETe. Seasonal ETewas greater than ET0 but less than ETr. From these results, we conclude that the EB procedure presented here, with portable instrumentation, constitutes a viable alternative method to lysimeters forquantifying ET quickly in cropping systems for irrigation water management applications. Additional testing of the EB method is recommended under a broader range of climatic, agronomic and soil conditions.