Crop Coefficient for Mulched Cotton Under Variable Irrigation Regimes

Abstract

Reduced cost of cultivation (30%) and increase in yield (40%) obliged the Saurashatra farmers to adopt Bt. Cotton on mass scale. Saurashtra cotton earns more profit at international market due to good luster, low naps, more wax on fibers surface, very low dye absorption. High evaporative conditions, scarcity of groundwater, and deficient rainfall condition are detrimental to cotton yields. Climatic change is adding another dimension to this complex nexus of soil-water-plant-atmosphere. Adverse environmental conditions coupled with water scarcity intrigued farmers of this region to adopt drip irrigation with mulch in Bt. Cotton for mitigating the impact of climatic aberrations. Determination of actual crop evapotranspiration during crop growing season is highly advantageous for sound irrigation scheduling. So far no study is reported to develop crop coefficient for drip irrigated biodegradable mulch cotton subjected to variable irrigation regimes. An experiment was undertaken consecutively for two years (2013-14 and 2014-15) to address this issue. Diurnal and temporal variation of soil moisture with depth was monitored using soil moisture sensors at irrigation regimes 1.0 IW/ETc and 0.8 IW/ETc. The control treatment was taken as drip with no mulch. Adjusted FAO K c predict higher value than sensor based K c values at both irrigation regimes. Sensor based K c-mid values were lower by 12.99% and 30.04% than the adjusted FAO K c-mid value at 1.0 IW/ET c and 0.8 IW/ET c respectively. Biodegradable plastic mulch reduced K c-ini value by 72.26% and 66.54% over control at 1.0 IW/ET c and 0.8 IW/ET c respectively. Overestimated adjusted FAO K c values caused a loss of 78.13mm and 66.54mm of precious water at 1.0 IW/ET c and 0.8 IW/ET c respectively. This study admonishes blind adoption of published FAO K c curves, for mulch conditions.

Determination of crop-coefficients and estimation of evapotranspiration of rapeseed using lysimeter and different reference evapotranspiration models

“…Penman-Monteith slightly underestimatedand Makkink and Priestly-Tailor models slightly overestimated the evapotranspiration. Contrary to it, Prajapati and Subbaiah (2019) found that adjusted FAO Kc overestimated evapotranspiration in Bt cotton in Junagadh. It suggested that local variability of meteorological conditions is important for estimation of reference evapotranspiration by different models.…”

Precision Irrigation Strategies for Wheat (Triticum aestivum L.) Farming: Influence of Drip Lateral Geometry, Irrigation Regimes and Frequency on Crop Performance

“…The use of flood irrigation, which has a poor water use efficiency (35-40%), is the main cause of the inadequate irrigation coverage . One of the main factors limiting irrigation coverage is the prevalent use of flood irrigation, which uses water inefficiently (Prajapati and Subbaiah, 2015;Prajapati et al, 2016). Because of significant conveyance and distribution losses, estimates of water use efficiency under the flood irrigation range from 35 to 40% (Rosegrant, 1997).…”