Trickle Irrigation of Okra Based on Small Pan Evaporation Schedule under Glasshouse Condition

Abstract

A small pan evaporation-based schedule for microirrigated okra (Hibiscus esculentus) was carried out using an experimentally derived evapotranspiration (ET_c) equation ET_c=α K_panK_c E_sp^b, where α and b were 0.58 and 1.3 respectively for the data used, K_pan is coefficient for class A pan evaporation, E_sp is evaporation from a small pan evaporation, and K_c is crop coefficient. For suitably selected K_pan and If, values, daily crop water needs were computed as irrigation requirements for three microirrigation treatments: porous cylindrical pot [subsurface cylindrical (SSC) source], porous rubber tube [subsurface line (SSL) source], and surface dripper [surface point (SP) source]. Fresh fruit yields of 2.30, 3.53, and 3.47 t ha^-1 were realized for the pot, rubber, and drip treatments respectively, compared with commercially reported yields of 2-3 t ha^-1. Water use efficiency (WUE) values were 2.35, 3.60, and 3.54 kg m^-3 for the pot, rubber, and drip treatments respectively. The yield differences are purely incidental and do not necessarily reflect the true potentials of the systems under investigation. Whereas the rubber and drip treatments were standard systems, the pot system was newly designed and hence suffered some technical hitches. Also, the equation used over-predicted irrigation requirements up to midseason but under-predicted requirements beyond mid-season.