Sub-surface drip irrigation studies in cotton-wheat cropping system
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Date
2023
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Punjab Agricultural University
Abstract
An increasing concern over the sustainability of the water resources in north-west India has stimulated an interest in drip irrigation. However, the high investment cost and the labour-intensive operation of removing laterals at the end of crop season discourage farmers to adopt surface drip irrigation in multiple cropping systems. Sub-surface drip laterals placed at suitable depth intended for multiple years could be a valid option for multiple cropping systems in northwest India. Therefore, a field experiment was conducted for the period of two years (2020-2021 and 2021-2022) to optimize lateral depth, emitter spacing and irrigation scheduling for sub-surface drip irrigated cotton-wheat cropping system. Experiment was laid out in a split-plot design using combinations of drip lateral depths (20, 25, and 30 cm), and emitter spacings (20, 30, and 40 cm) in main plots and irrigation schedules (100% ETc, 80% ETc, and 60% ETc) in sub-plots. Different combinations of sub-surface lateral depths and emitter spacings were compared with two additional controls (flood irrigation and surface drip irrigation). Seed cotton yields were comparable for lateral depths ranging from 20 to 30 cm, and emitter spacings ranging from 20 to 40 cm. Wheat yields and total system productivity were reduced with deeper lateral depth of 30 cm in dry year. A 7.9% reduction in system productivity was observed with deeper placement of laterals at 30 cm relative to 20 cm depth in drier year. Emitter spacings reduced wheat yields however, system productivity remained unaffected. Irrigation at 100% ETc resulted in highest productivity of cotton-wheat cropping system. Sub-surface drip placement depth of 20 cm resulted in highest total water productivity for cotton-wheat cropping system which was comparable with drip lateral depth of 25 cm. Sub-surface drip placement depth of 20 cm resulted in highest energy efficiency and net returns of cotton-wheat cropping system which were comparable with drip lateral depth of 25 cm. Closer emitter spacing of 20 cm was most energy efficient during dry year. Irrigation at 100% ETc resulted in highest energy efficiency and highest net returns of cotton-wheat cropping system which was comparable with irrigation at 80% ETc. Irrigation at 80% ETc through sub-surface drip system improved the net returns by 10.3-19.6% over flood irrigation while saving 38.3-44.7% irrigation water relative to flood irrigation. These findings emphasize that it is economically viable to invest in sub-surface drip irrigation using 20 cm lateral depth, 20-40 cm emitter spacing and irrigating at 80% ETc, increasing water productivity while having higher yield and profitability than flood irrigation and surface drip irrigation.
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Citation
Preksha (2023). Sub-surface drip irrigation studies in cotton-wheat cropping system (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.