Abstract

                               High evaporative conditions, scarcity of groundwater and deficient rainfall condition are detrimental to cotton yields in Saurashtra region of Gujarat. Climatic change adds 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. So far, no study has reported the conjunctive impact of different mulches (silver black plastic mulch and biodegradable plastic mulch), irrigation regimes (0.6, 0.8, and 1.0 ETc) and frequency (2, 3 and 5 days) on economic productivity of Bt. cotton. An experiment was undertaken consecutively for two years (2013-14 and 2014-15) to address this issue. Irrigation scheduling was done based on actual evapotranspiration measured with help of soil moisture sensors. The control treatment was taken as drip with no mulch. Silver black plastic mulch recorded the highest plant height (1.92m), number of sympodial (30.9) and monopodial branches (6.1), number of bolls (61.5), mean boll weight (4.77g), seed cotton yield (4661 kg ha-1), water use efficiency (20.48 kg ha-1mm-1) at 0.8 ETc and 3 days of irrigation frequency. These attributes increased with increase in irrigation regimes and decreased with increase in irrigation frequency in control treatment. The highest benefit cost ratio of 3.28 and internal rate of return of 141.52% was observed in silver black plastic mulch at
0.8 ETc and 3 days of irrigation frequency and the lowest was observed in no mulched treatment at 0.6 ETc and 5 days of irrigation frequency.

Key words : Plastic mulch, Drip irrigation, Moisture regimes, Irrigation frequency