Crop coefficients according to plant density and substrate volume in sweet pepper under greenhouse

The objective of this study was to determine the effect of two planting densities (1.4 and 2.4 plants m(-2)) and three volumes of substrate plant(-1) (7, 14 L and 21 L) on the K-c of sweet pepper (Capsicum annuum) in coconut fiber in a greenhouse. The experiment was carried out from April 22 to August 28, 2016, at the Fabio Baudrit Moreno Agricultural Research Station, Alajuela, Costa Rica. It was used a three complete randomized blocks experimental design with a bifactorial treatment arrangement. The K-c were obtained as the ratio between the crop evapotranspiration (ETc) obtained by the water balance method, and the reference evapotranspiration (ETo) according to Penman-Monteith FAO-56. The K-c of sweet pepper hydroponic under greenhouse were not affected by the interaction between plant density and substrate volume (P> 0.05); however, both factors affected (P< 0.05) individually, with a more significant effect of the density factor. Indistinctly the substrate volume, the K-c were reduced in average 33%, going from 2.4 plants m(-2) to 1.4 plants m(-2). Independent of plantation density, the most significant reduction (11.5%) in Kc occurred when the volume decreased from 21 L to 7 L of substrate plant(-1). Plant density and amount of substrate affected the ETc and consequently the K-c of the hydroponic crop of greenhouse sweet pepper. The technique of hydroponic greenhouse crop along with the climate and cultivation practices reflected appreciable differences between K-c FAO-56 values and the K-c obtained in the sweet pepper cultivated.