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Subsurface drip irrigation in arid areas has the potential to replace traditional mulched drip irrigation to achieve green and sustainable cotton production. However, the suitable irrigation amount and frequency are still unclear, which seriously limits the ability of this model to improve water productivity and water-saving potential. Therefore, a field experiment was carried out from 2021 to 2023; a split plot experimental design was adopted with two irrigation amounts (W1, 3177 m3 ha−1; W2, 3840 m3 ha−1) and three irrigation frequencies (F1, 9; F2, 8; F3, 7). The effects of different irrigation strategies on the soil microenvironment, moisture content, biomass, and water use efficiency (WUE) of cotton organs were evaluated. The W2 treatment improved the soil moisture content, increased the soil temperature gradient, and reduced the soil conductivity, thereby increasing the moisture content and biomass of various organs. Moreover, compared with the F1 treatment, the F2 and F3 treatments were more likely to increase the soil moisture content, soil temperature gradient, WUEStem, WUELeaf and WUEBoll. In addition, the water consumption of the F2 and F3 treatments decreased by 3.9 % and 0.9 %, respectively, compared with that of the F1 treatment. These findings indicate that W2F2 can reduce water consumption while increasing boll biomass and WUEBoll. Further analysis revealed that under W2F2, WUEBoll was positively correlated with soil temperature gradient and soil conductivity and negatively correlated with leaf moisture content (LMC) and water consumption. In summary, with an irrigation amount of 3840 m3 ha−1, delaying the initial irrigation event and increasing the irrigation quota (8 irrigation events) improve the water environment in cotton fields, reducing soil temperature fluctuations and surface salt accumulation and synergistically increasing the boll biomass of cotton organs and WUEBoll. This irrigation strategy represents an effective cotton cultivation method to maximize cotton yield and improve resource utilization efficiency.

Chemical topping with 1,1-dimethylpiperidinium chloride (DPC) has been considered a promising measure to inhibit apical dominance in cotton (Gossypium hirsutum L.). However, knowledge of the plant growth and canopy development of cotton under chemical topping with DPC remains limited, and the effect of this practice on lint yield and defoliation is unclear. A two-year (2019–2020) field experiment was conducted with two varieties, Xinluzao 60 (L60, DPC-insensitive) and Jinken1402 (JK1402, DPC-sensitive), and four topping methods, manual topping (MT), no topping (NT), DPC+ (fortified DPC) and DPC. We found that the lint yields of L60 and JK1402 treated with DPC were equivalent to those of L60 and JK1402 treated with DPC+ but were enhanced by 0.9–4.7% in L60 and 6.7–11.8% in JK1402 relative to those under MT and NT, with no significant difference in fiber quality. This was mainly due to the change in plant growth and canopy structure. In particular, compared with MT, application of DPC shortened the upper branches and extended the duration of the leaf area index peak. Moreover, in the late reproductive period, DPC application increased the number of upper leaves and reduced diffuse noninterceptance. Notably, the light transmittance rate (LLR) of JK1402 treated with DPC was higher than that of MT in the middle and lower parts of the canopy. Furthermore, there was positive correlation between LLR and defoliation rate. Therefore, chemical topping with DPC provided an effective alternative for manual topping.

IntroductionLow agricultural nutrient input efficiency remains a significant impediment for crop production globally. To address this issue in cotton agroecosystems, there is a need to develop sustainable crop nutrient management strategies to achieve high crop yields. We hypothesized that organic liquid fertilizer (OF) combined with reduced chemical fertilizer (CF) would enhance cotton yield by improving leaf functioning and soil properties. However, the underlying mechanism and its related process is poorly understood.MethodsThis study explored the effects of OF combined with reduced CF on cotton yield, physiology and soil properties. Treatments included a single application of CF (CF: N, P2O5 and K2O applied at 228, 131 and 95 kg ha−1) and combined applications of OF and CF (OF0.6−OF1.4) in the following ratios: OF0.6, OF+60% CF; OF0.8, OF+80% CF; OF1.0, OF+100% CF; OF1.2, OF+120% CF; OF1.4, OF+140% CF. Results and discussionThe result showed that compared with CF, OF0.8, OF1.0 and OF1.2 increased soil organic matter (SOM) content by 9.9%, 16.3% and 23.7%, respectively. Compared with CF, the OF0.6, OF0.8, OF1.0, and OF1.2 treatments increased leaf area (LA) by 10.6−26.1%, chlorophyll content (Chl content) by 6.8−39.6%, and the efficiency of photosystem II (PSII) light energy (Y(II)), electron transfer rate of PSII (ETR) and photochemical quenching (qP) by 3.6−26.3%, 4.7−15.3% and 4.3−9.8%, respectively. The OF0.8 treatment increased net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (E) by 22.0%, 27.4% and 26.8%, respectively, resulting in higher seed cotton yield. The seed cotton yield and economic coefficient were positively correlated with Pn, E, Gs and Y(II) from the full boll stage to the boll opening stage. In summary, the OF0.8 treatment can maintain a high SOM content and photosynthetic performance with reduced chemical fertilizer input without sacrificing yield. The integration of OF+80% CF (OF0.8) is a promising nutrient management strategy for highly efficient cotton production under mulch drip irrigation systems.

The use of industrial waste as an agricultural resource is important for clean and sustainable agriculture. We assumed that industrial organic wastewater coupled with chemical fertilizer would increase cotton yield by enhancing nutrients absorption and utilization. To test this hypothesis, a two-year (2019–2020) field trial was conducted to assess the impacts of CK (0 kg ha−1), chemical fertilizer (CF) (N-P2O5-K2O: 228-131-95 kg ha−1), chemical fertilizer + organic wastewater (F0.6 (60%CF + OW: 1329 kg ha−1), F0.8 (80%CF + OW), F1.0 (CF + OW), F1.2 (120%CF + OW) and F1.4 (140%CF + OW)) on nutrient absorption and distribution, fertilizer use efficiency and cotton yield under drip irrigation system. Compared with CF, the soil organic matter, NH4+-N and AV-K increased significantly after F0.8-F1.4 treatments. The absorption of nitrogen (N), phosphorus (P) and potassium (K) by plants after dripping organic wastewater (F0.8-F1.4) increased by 1.1–11.2% as compared with CF (F0.6, CF < F0.8, F1.0 < F1.2, F1.4). Under F0.8, treatment resulted in a higher distribution rate of N, P and K in reproductive organs compared with other counterparts. In addition, drip application of organic wastewater promoted the absorption of magnesium (Mg) and zinc (Zn) in leaves and Fe in roots with higher translocation of Zn and boron (B) to reproductive organs compared with other treatments. The absorption of N, P and K was positively correlated with Mg, negatively correlated with calcium (Ca) and sulfur (S), and positively correlated with manganese (Mn) and iron (Fe). The yield and fertilizer utilization rate of cotton were higher at F0.8. Conclusively, the use of 1329 kg ha−1 organic wastewater (organic mattered ≥ 20%, humic acid ≥ 20 g L−1, Bacillus subtilis ≥ 2 × 108 L−1) combined with chemical fertilizer (N-P2O5-K2O) at (182-104-76 kg ha−1) reduces the application of chemical fertilizer and can increase utilization efficiency of chemical fertilizer with a high cotton yield under mulch drip irrigation in arid regions.

The application of organic liquid fertilizer combined with chemical fertilizer is one of the key technologies used to simultaneously improve cotton yield and efficiently utilize resources. However, organic fertilizer is usually applied once as a base fertilizer during production, and few studies have been conducted on topdressing with water during the growth period. Therefore, in this study, Xinluzao 74 was used as the experimental material, and a single fertilizer application (CF) was used as a control in 2019–2020 under the conditions of integrated control of water and fertilizer with mulch drip irrigation. Five combinations of reduction in chemical fertilizer combined with organic fertilizer (OF1, OF2, OF3, OF4, and OF5) were used to investigate the influences of chemical fertilizer combined with organic liquid fertilizer on the leaf area index (LAI), canopy openness (DIFN), mean foliage tilt angle (MTA), photosynthetically active radiation (PAR), canopy apparent photosynthesis (CAP), and yield and quality of cotton. The results show that among the different fertilization treatments, the OF2 treatment had the best results, not only ensuring a suitable LAI (4.8) and maintaining a large DIFN (0.1) but also increasing the light transmittance of the middle and lower canopies (0.02–0.03). At the same time, CAP increased significantly compared with that in the CF treatment, with an average increase of 12.8%. The high value lasted for a long time, and the late decay stage remained at 8.9 μmol m−2 s−1. The ratio of the population respiration rate to total photosynthesis (CR/TCAP) decreased significantly, with an average decrease of 13.5%. Compared with that in CF, the lint yield increased by 27.0% in the other treatments. The correlation analysis showed that lint yield was positively correlated with the relative chlorophyll content (SPAD value), PAR transmittance (PARU) and CAP in the upper canopy (p < 0.05) and significantly negatively correlated with PAR transmittance (PARM) in the middle canopy and PAR transmittance (PARD) and CR/TCAP in the lower canopy (p < 0.05). Therefore, under mulch drip irrigation, the OF2 treatment (OF + 80% CF) improved the canopy structure of cotton at the late growth stage, increased the population photosynthetic rate, and increased lint yield significantly; thus, this approach can be used as an effective fertilization method to achieve the goal of decreasing costs and increasing efficiency in cotton production.