Pre-and post-sowing irrigation scheduling impacts on crop phenology and water productivity of cotton (Gossypium hirsutum L.) in sub-tropical north-western India

Abstract

The establishment of growth stage specific irrigation scheduling is considered critically important for achieving higher cotton (Gossypium hirsutum L.) productivity in north-western India. In the study region, farmers prefer pre-sowing irrigation (PSI) with canal water because underground water has poor quality due to presence of high concentration of soluble salts. However, non-availability of canal water at cotton sowing period often delays its sowing, and eventually impacts cotton productivity with significant effect on crop phenology. Therefore, we investigated the effect of irrigation scheduling based on depth of PSI and subsequent post-sowing first irrigation (PSFI) on crop phenology, growth attributes and water productivity of cotton at different dates of sowing (DOS) which are representative of actual sowing window in the study region. More specifically, this study evaluated the performance of PSI depths (viz. 75 and 120 mm; PSI75 and PSI120) and DOS (viz. April 30th and May 30th) combinations in main plots, and PSFI treatments (i.e. 21–42 DOS; PSFI21, PSFI28, PSFI35 and PSFI42) in the subplots. These results revealed that PSI120 significantly (p < 0.05) increased the seed cotton yield (by ∼16.8–18.7 %), real crop water productivity (RCWP; by ∼15.9–17.9 %) and total crop water productivity (TCWP; by ∼11.0 %), compared with PSI75. The April 30th sown cotton showed improved phenological development; apparently due to longer yield formation phase which has significantly increased the seed cotton yield (by ∼87.8–97.6 %), apparent water productivity (by ∼77.3–79.0 %), RCWP (by ∼61.2–71.1 %) and TCWP (by ∼77.3–88.3 %), compared with May 30th sown crop. Therefore, to achieve higher cotton productivity under PSI75 treatment, PSFI21–35 appeared most optimum, whilst under PSFI28–42 significantly outperformed under PSI120. The PSI120 treatment significantly improved the lint yield and ginning outturn (GOT), compared with PSI75. The number of monopods/sympods, bolls m−2 and boll weight were significantly higher at PSFI28; which decreased with delayed PSFI. The effect of PSI and PSFI on crop productivity was significantly higher for April 30th sown crop, compared with May 30th sown crop. The days to square initiation exhibited a linear significant relationship with flower initiation (R2 =0.797 *; p < 0.05), boll development (R2 =0.857 *; p < 0.05), boll opening (R2 =0.735 *; p < 0.05) and crop maturity (R2 =0.779 *; p < 0.05). GOT exhibited a linear significant relationship with fibre span length (R2 =0.709 *; p < 0.05). These results highlight that irrigation scheduling at PSI120 and PSFI28–42 for 30th April sown crop significantly enhanced the crop and water productivity. Nonetheless, PSI120 helped delay the PSFI for both sowing dates without any significant impact on cotton productivity. The economic indices viz. average gross returns (AGRs), average net returns (ANRs) and benefit-cost (B-C) ratio of cotton cultivation were significantly higher under PSI120 and PSFI28–35.