Weeding effects on crop transpiration and weed water use: quantification
1999
Van der Meer, F-B. | Twomlow, S.J. | Bruneau, P. (Silsoe Research Institute, Bedford (U.K.)) | Reid, I. (Loughborough University, Loughborough (UK). Department of Geography)
In Zimbabwe, drought severely limits maize production, especially on poor, sandy soils in the communal areas. Weed transpiration exacerbates the problem. Correlating crop responses with water conservation practices requires an accurate assessment of the soil water balance. Three methods to calculate evapotranspiration and drainage were compared. Data came from a weeded and an unweeded fallow, and a weeded and unweeded crop. The methods were a simple weekly soil water balance (SWB), a method which used an exponential decay curve to generate a daily estimate of soil moisture and evapotranspiration, and a functional crop growth model. The seasonal evapotranspiration estimate was much higher with the SWB than with the other methods, because it overestimated evaporation due to the weekly time step. Also when the four treatments were compared, the SWB deviated from the other methods. These showed the same trends, more pronounced differences between treatments, and they separated evaporation and weed water use from crop transpiration. The simplicity of the SWB makes it a practical, qualitative tool to compare within-trial differences. The higher accuracy of the other methods, and the better opportunities for extrapolating the results to neighbouring agro-ecological environments, should be weighted against their greater complexity and the research needs.
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