Osmo-protectants improve cotton yield by alleviating moisture stress under semi-arid conditions

In north-western India, short-term droughts due to insufficient rainfall or irrigation canal closures are common. To quantify seed cotton yield (SCY) loss under moisture deficit and evaluate the efficacy of foliar-applied osmo-protectants (OPs), a 2-year field experiment was conducted with three moisture regimes (M-1: well watered, M-2: rainfed after single post-sowing irrigation [POSI], and M-3: rainfed after two POSIs) in main plots and eight OPs (S-1: control, S-2: four sprays of 2% urea at weekly intervals, S-3: four sprays of 2% KNO3 at weekly intervals, S-4: single spray of 500 mg kg(-1) thio urea [TU], S-5: single spray of 50 mg kg(-1) salicylic acid [SA], S-6: single spray of 100 mg kg(-1) glycine betaine [GB], S-7: single spray of 100 mg kg(-1) SA, and S-8: three sprays of 1% pink pigmented facultative methylobacteria at 10 days interval) in sub-plots of a split plot design. Moisture stress induced a reduction of relative water content (RWC) and consequently decreased SCY by 17% and 32.9% under M-3 (2821 kg ha(-1)) and M-2 (2291 kg ha(-1)), respectively, compared to M-1 (3418 kg ha(-1)). Except for TU, all tested OPs improved SCY by 6.3%-23.7% in comparison to the nontreated control. Application of SA and GB enhanced photosynthesis, improved stomatal conductance, and maintained higher RWC. Application of SA at 100 mg kg(-1) resulted in an additional income of US$458 ha(-1) and was the most economical treatment for countering short-term drought.