The in¯uence of crop canopy on evapotranspiration and crop coef®cient of beans Phaseolus vulgaris L.) Gerson A. de Medeiros a,* , Fla Âvio B. Arruda b , Emõ Âlio Sakai b , Mamor Fujiwara b a Centro Regional Universita Ârio de Espõ Ârito Santo do Pinhal Ð CREUPI, Espõ Ârito Santo do Pinhal, CP 05, SP, Brazil CEP 13990-000 b Instituto Agrono Ãmico, Campinas, SP, Brazil Accepted 16 October 2000 Abstract Experiments were conducted to investigate the effect of crop development on evapotranspiration and yield of beans Phaseolus vulgaris L.) at the Instituto Agrono Ãmico IAC), Campinas, State of Sa Äo 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 ®eld. 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 coef®cient k cb ) and crop coef®cient k c ), demonstrating the strong dependence of both coef®cients on canopy development. A simulation study was carried out and showed that k cb based on LAI would allow good estimates of water use for different plant density populations in the ®eld. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Bean; Irrigation; Crop coef®cient; Leaf area index; Ground cover 1. Introduction Irrigation water management aims to provide sufficient water to replenish depleted soil water in time to avoid physiological water stress in the growing plants. Hence, a good Agricultural Water Management 49 2001) 211±224 * Corresponding author. Fax: 55-19-651-3654. E-mail addresses: gerson_medeiros@creupi.br G.A. de Medeiros), farruda@cec.iac.br F.B. Arruda), emilio@cec.iac.br E. Sakai). 0378-3774/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0378-377400)00150-5