Crop coefficients of Bt. cotton under variable moisture regimes and mulching

Abstract

An experiment was undertaken for two years (2013-14 and 2014-15) on sandy loam soils of Junagadh (21°30’ N, 70°27’ E) to determine crop coefficients of Bt. cotton under three mulch treatments (M1- silver black plastic mulch, M2- biodegradable plastic mulch, M3- wheat straw mulch and C - control) with two irrigation regimes (I1- 1.0 IW/ETc, I2-0.8 IW/ETc). Actual evapotranspiration was estimated using soil moisture sensors. Results revealed that adjusted FAO Kc predicts higher value than sensor based Kc values at both irrigation regimes. Silver black plastic mulch recorded lower crop coefficient values at all growth stage of Bt. cotton compared to biodegradable plastic mulch, wheat straw mulch and control. Sensor based Kc ini and Kc-devvalues of silver black plastic mulch observed 72.2, 29.0 and 66.9 and 14.8 per cent lower than control at 1.0 IW/ETc and 0.8 IW/ETc respectively. Overestimated adjusted FAO Kc values caused a loss of 78.1mm and 66.5mm of precious water at 1.0 IW/ETc and 0.8 IW/ETc respectively. This study admonishes blind adoption of published FAO Kc curves for mulch conditions.