Irrigation planning in cotton through simulation modeling |
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Authors: | R Singh Joginder Singh |
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Institution: | (1) Indo-Dutch Project, Department of Soil Science, CCS Haryana Agricultural University Hisar-125004, Haryana, India, IN |
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Abstract: | Experiments were undertaken at CCS Haryana Agricultural University Farm, Sirsa (India) to estimate the optimum irrigation
schedule for cotton resulting in minimum percolation losses. The sprinkler line source technique was adopted for creating
various irrigation regimes at different crop growth stages. The SWASALT (Simulation of Water And SALT) model after calibration
and validation provided water balance components. The wa-ter management response indicators (WMRI's) such as transpiration
efficiency Et/(Irr + P), relative transpiration Et/Etp, evapotranspiration efficiency ET/(Irr + P), soil moisture storage change ΔW/Wint (deficit/excess) and percolation loss Perc/(Irr. + P) were evaluated using water balance components as estimated by the simulation
study. Under limited water supply conditions, the optimum irrigation depth was found to be 57 mm at crop growth stages with
pre-sowing and 1st irrigation of 120 mm and 80 mm respectively for sandy clay loam underlain by sandy loam soil (Type I). The corresponding
values of relative transpiration, transpiration efficiency and evapotranspiration efficiency were 0.65, 0.65 and 0.89 respectively.
The crop yield varied linearly with increasing irrigation depth which was evident from increase in relative transpiration
with increasing depth of water application. However, increased depth of irrigation resulted in less moisture utilisation from
soil storage (20% depletion at 40 mm depth and 4.4% moisture built up at 100 mm depth). The extended simulation study for
sandy soil underlain by loamy sand (Type II) indicated that two pre-sowing irrigations each 40 mm and subsequent irrigations
of 40 mm at an interval of 20 days depending upon rainfall were optimum. This irrigation scenario resulted in zero percolation
loss accompanied by 74% relative transpiration and 14 per cent soil moisture depletion.
Received: 20 November 1995 |
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