The influence of crop canopy on evapotranspiration and crop coefficient of beans (Phaseolus vulgaris L.)

Experiments were conducted to investigate the effect of crop development on evapotranspiration and yield of beans (Phaseolus vulgaris L.) at the Instituto Agronômico (IAC), Campinas, State of São Paulo, Brazil, during the dry season of 1994. A completely randomized design was carried out with three population density treatments and four replications. The treatments were: (a) crop sown in evapotranspirometers at a density of 50 plants m−2, and thereafter thinned to 25 plants m−2, when the canopy achieved full ground cover; (b) crop sown with population densities of 14 and 28 plants m−2 in an irrigated field. Crop growth was evaluated considering dry matter (DM), vegetative ground cover (GC%) and leaf area index (LAI). These parameters were successfully related to basal crop coefficient (kcb) and crop coefficient (kc), demonstrating the strong dependence of both coefficients on canopy development. A simulation study was carried out and showed that kcb based on LAI would allow good estimates of water use for different plant density populations in the field.