Humus is the stable form of added crop and animal residues. The organic matter after a long-term decomposition process converts into humic substances. The naturally occurring humus is present in less amount in soils of the arid and semi-arid regions. The addition of commercially available humic acid can, therefore, contribute to improving soil health and crop yields. The present study was conducted to evaluate the effect of potassium humate, applied through soil seed dressing, on cotton productivity and fiber quality attributes. Seed dressing with potassium humate was done at the rate of 0, 100, 150 and 200 mL kg⁻¹ seed while in soil potassium humate was applied at the rate of 0, 10, 20 and 30 L ha⁻¹. Results showed that the combined application of potassium humate by seed dressing and through soil application improved the soil properties, productivity and fiber quality traits of cotton. All levels of soil applied potassium humate (10, 20 and 30 L ha⁻¹) performed better over seed dressing in terms of cotton productivity and fiber quality attributes. Among the soil application rates, 20 L ha⁻¹ potassium humate proved better as compared to other rates (0, 10 and 30 L ha⁻¹). Higher soil application of potassium humate (30 L ha⁻¹) showed depressing effects on all the traits studied like the reduction of 12.4% and 6.6% in Ginning out turn and fiber length, respectively, at a seeding dressing of 200 mL kg⁻¹. In conclusion, potassium humate seed dressing and soil application at the rate of 200 mL kg⁻¹ and 20 L ha⁻¹, respectively, is a better approach to improve cotton productivity. Soil potassium humate should not exceed a rate of 20 L ha⁻¹ when the seed dressing of potassium is also practiced.

The socio-economic development of a country is highly dependent on water availability. Nowadays, increasing water scarcity is a major global challenge. Continuing improvements in water-use efficiency are essential for cotton production sustainability. Reduced irrigation in cotton could be a solution to water shortage in the arid climate without compromising the cotton yield. Therefore, a two-year field study was conducted to assess the effect of two levels of irrigation i.e., 50% and 100% of available water content (AWC) on the yield of four cotton genotypes (CIM-678, CIM-343, CRIS-613, and CYTO-510). The maximum seed cotton yield was observed in CIM-678, which was 2.31 and 2.46 Mg ha⁻¹ under 100% AWC during 2018 and 2019, respectively, and was non-significantly reduced by 7.7 and 8.94%, owing to deficit irrigation. The maximum water use efficiency (WUE) of 0.55 and 0.64 Kg ha⁻¹ mm⁻¹ was observed under 50% AWC in CIM-678, which was significantly higher than WUE at 100% AWC during both years. Leaf area index and physiological parameters such as photosynthesis rate, transpiration rate, and stomatal conductance were not significantly affected by deficit irrigation. So, it was concluded that the reduced irrigation technique performed well without significant yield loss, improve WUE, and saved 37 cm of water that could be used for other crops or to increase the area of the cotton crop.

Low nitrogen-use efficiency (NUE) is a serious issue for cotton production and environmental sustainability in arid climates. A pot study was conducted to evaluate the effect of K nutrition on NUE and performance of low- and high-K-efficiency cotton cultivars under two moisture regimes. Treatments included two soil moisture levels—i.e., normal irrigation, 100% available water content (AWC); reduced irrigation, 50% AWC—three levels of nitrogen (N)—i.e., 0, 375, and 750 mg N pot⁻¹—and two K levels, i.e., 0 and 208 mg K pot⁻¹. Results reveal that 208 mg K pot⁻¹ application with nitrogen significantly enhanced the N-use efficiency, growth, and yield attributes of both cotton cultivars compared with sole N fertilization. Similarly, the combined application of NK @ 375 N + 208 K mg pot⁻¹ caused up to 83% increase in NUE under AWC_50% and AWC_100%, as compared with NK control (0 N + 0 K). Compared with the control, imposed low-moisture stress caused a decrease of 13.9% in stomatal conductance (g_s), 2.5% in transpiration rate (E), and 6.5% in net photosynthetic rate (P_N), respectively_. The physiological water use efficiency (P_N/E) decreased by 13.2% under AWC_50%. Applied NK @ 375 N:208 K, mg pot⁻¹ caused 27.39 and 27.56% improvement in the P_N/E in HKE and LKE cultivars under AWC_50%, respectively. The HKE cultivar, i.e., CIM-554, maintained the highest g_s and P_N than FH-901, that was low-K-efficiency cultivar. The study suggests that varietal selection and adequate K fertilization have the prospects to improve NUE and save considerable quantities of fertilizer and irrigation water in cotton production under arid environments.

The introduction of transgenic cotton (Bt-cotton) for controlling bollworms has resulted in increased production; however, the residual effects of mulches from Bt-cotton are poorly understood. Therefore, the current study evaluated the impact of Bt and non-Bt cotton mulches on soil properties, weed dynamics and yield of winter crops sown after cotton. Three different winter crops, i.e., wheat (Triticum aestivum L.), canola (Brassica napus L.) and Egyptian clover (Trifolium alexandrinum L.) and two mulch types, i.e., Bt mulch (obtained from Bt-cotton cultivars, i.e., ‘CIM-616’ and ‘GH-Mubarik’) and non-Bt mulch (obtained from non-Bt cultivars, i.e., ‘CIM-620’ and ‘N-414’) were included in the study. The mulches were applied at a rate of 2 t ha^-1 before planting the winter crops. The Bt and non-Bt mulches differentially affected soil properties, weed dynamics and productivity of winter crops. The non-Bt mulches decreased the soil bulk density and penetration resistance, while increased the soil porosity. Wheat crop increased the soil porosity, pH, available N and soil organic matter content. Overall, non-Bt mulches improved the productivity of winter crops compared with Bt mulches. The toxins released by Bt mulches lowered the weed density; however, it negatively influenced soil properties (bulk density and available nitrogen) and productivity of winter crops. Therefore, appropriate crop rotation measures may be opted for the soils cultivated with Bt-cotton to conserve soil and achieve yield sustainability for the crops sown after cotton. Nonetheless, non-Bt mulches can be used for improving soil properties and productivity of winter crops.

Cotton (Gossypium hirsutum L.) is one of the major fiber crops. Its production is under threat due to scarcity of water resources under a changing climatic scenario. Limited water availability also decreases the uptake of phosphorus, and less uptake of phosphorus can deteriorate the quality attributes of cotton fiber. There is a need to introduce bio-organic amendments which can mitigate osmotic stress on a sustainable basis. Inoculation of rhizobacteria can play an imperative role in this regard. Rhizobacteria can not only improve the growth of roots but also enhance the availability of immobile phosphorus in soil. That is why the current experiment was conducted to explore and compare the efficacy of sole application of diammonium phosphate (DAP) over plant growth-promoting rhizobacteria (PGPR) and phosphorus solubilizing bacteria (PSB) coated DAP on growth and quality attributes of cotton under artificially induced osmotic stress at flowering stage. The impact of phosphorus levels was found to be significant on the plant height, leaf area, average boll weight, stomatal conductance, net photosynthetic rate, and seed cotton yield, while the irrigation effect was significant on all the parameters. The PGPR coated phosphorus performed better as compared to other treatments under normal irrigation and osmotic stress. Results showed that PGPR coated phosphorus increased by 29.47%, 21.01%, 41.11%, 32.73%, 15.63% and 22.89% plant height, average boll weight, stomatal conductance, net photosynthetic rate, fiber length, and seed cotton yield respectively. In conclusion, PGPR coated DAP can be helpful to get higher cotton productivity as compared to control and sole application of DAP under normal irrigation and osmotic stress.

The present study was planned to explore the relationship between soil chemistry with bacterial population of Bt and non-Bt cotton and their phenotypic and molecular characteristics. The pre-plant soil and rhizospheres of Bt and non-Bt cotton were collected and analyzed for some soil parameters and bacterial population. The bacterial isolates were analyzed for their morphological, biochemical, and molecular characteristics. Bacterial population showed a significant (p < 0.05) positive correlation with clay content, electrical conductivity, organic matter, total nitrogen, and available phosphorus and potassium negative with correlation with pH. Bt cotton showed a non-significant effect on the soil parameters, significant decrease in bacterial population, change in the morphological and biochemical characteristics of rhizobacteria and replacement of four bacterial species with five new ones suggests the potential effect of Bt cotton on its rhizoflora. The rhizosphere of non-Bt cotton cultivated in the fertile agriculture field was found to be the best for bacterial growth.