Cotton Response to Water and Salinity under Sprinkler and Drip Irrigation
- A. Meiri ,
- H. Frenkel and
- A. Mantell
Knowledge of crop response to water is essential for proper irrigation management. The wide-spread introduction of drip irrigation, together with the increasing use of brackish water for cotton (Gossypium hirsutum L.) has made it necessary to examine how these variables effect its production function. A field study was conducted to determine the interaction of water salinity (3.7–7.8 dS m−1), irrigation method (sprinkler and drip), water amount (236–780 mm), irrigation interval (1–14 d), and plant density (intra-row spacing of 8 or 12.5 cm) on ‘Acala SJ-2’' cotton grown on a sandy-loam loess soil (Calcic Haploxeralf). With sprinkler irrigation, the two-piecewise curves that describe the yield response to water application differ in slopes, intercepts, and break points for the different salinites and irrigation intervals. The crop used more stored soil water at low salinity, low irrigation amount, and long irrigation interval. When we evaluated crop response to the sum of applied water and amount of stored water used, we found that the intercepts were nearly eliminated and the four slopes were combined, while the break points remained lower for the higher water salinity. The break points determine the water amounts above which other factors become limiting. The response function for drip irrigation had no break point, but had the same slope and intercept as the sprinkler treatments. The common production functions for seed cotton and total dry matter yield were Y kg ha−1 = −26.5 kg ha−1 + 9.21 kg ha−1 mm−1 × Wmm and Y kg ha−1 = −338 kg ha−1 + 21.2 kg ha−1 mm−1 × Wmm, respectively, where Y = yield, and W = sum of seasonal water application plus depletion of stored soil water. Water salinity, irrigation method and frequency, and intrarow spacing did not affect the linear response of seed cotton or dry matter yields to water when factors other than water availability were not limiting.
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