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.
Highlights
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
No studyis reported to develop crop coefficient for drip irrigated silver black plastic mulch, biodegradable plastic mulch and wheat straw mulch cotton subjected to variable irrigation regimes in this region
Crop coefficient curves for silver black plastic mulch, biodegradable plastic and wheat straw mulched cotton was developed for two irrigation regimes
Summary
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. Major constraints for reducing the water productivity are lack of knowledge on irrigation scheduling for mulched cotton and poor design of the drip system (Hajare et al, 2008 and Rajendra et al, 2012).Determination of crop evapotranspiration (ETc) is the most fundamental requirement for proper scheduling of irrigation Jaspinder Kaur et al, 2017). The FAO-56 promotes Penman-Monteith (P-M) combination equation which requires data of temperature, relative humidity, wind speed, and solar radiation. This data demand is the main constraint on its use in locations where climate data are limited (Rahimikhoob, et al, 2012). No studyis reported to develop crop coefficient for drip irrigated silver black plastic mulch, biodegradable plastic mulch and wheat straw mulch cotton subjected to variable irrigation regimes in this region. The study was undertaken to develop the Kc curves for drip irrigated mulched cotton using soil moisture sensors installed at different depths
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