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• Limited irrigation under high population levels are beneficial in terms of saved irrigation without reducing yield. • Leaf area index and radiation use efficiency in upper and middle canopy provides carbohydrates during boll formation. • Improvements in lint yield and water use efficiency depends on effective conservation of radiation use efficiency. Increasing plant density under insufficiency or deficit irrigation is considered a new water-saving technique in cotton production, especially in Xinjiang, China, an arid area with a short growing period. Increasing plant density reduces light intensity within the canopy; therefore, we hypothesized that resource use efficiency may be the main factor affecting cotton yield and water use efficiency under limited irrigation conditions. To test this hypothesis, 2-year field experiments were conducted to explore the effects of two irrigation patterns (I 500 , conventional irrigation; I 425 , limited irrigation) and three planting densities (D 12 , 12; D 24 , 24; D 36 , 36 plants m−2) on cotton yield, fiber quality, light interception rate, canopy photosynthesis and irrigation water use efficiency (IWUE). I 425 D 36 raised yield and IWUE by 1.40–22.4% and 13.4–34.5%, respectively, but it did not affect fiber quality compared with other treatments. Further, I 425 D 36 increased the leaf area index and the top- and middle-canopy light interception rates after 105 days after sowing, which improved the canopy apparent photosynthetic rate. Seed cotton yield was associated with leaf area index and the top- and bottom-canopy light interception rates. We conclude that irrigation of cotton with limited irrigation at a 425-mm level and a plant density at 36 plants m−2 had significant benefits in terms of economized irrigation without reducing yield in arid areas. [ABSTRACT FROM AUTHOR]

The plant growth regulator mepiquat chloride (1,1-dimethylpiperidinium chloride, DPC) has been successfully used worldwide in cotton production. Fortified DPC (DPC+) can slightly damage young tissues of the epidermis, which has shown potential in cotton chemical topping in China. The underlying mechanism remains unclear. We investigated whether apical meristem and leaf morpho-physiological traits contribute to delayed growth of the main stem and increased seed yield in DPC or DPC+ as a chemical inhibitor. Two different DPC-sensitive varieties (Xinluzao 60, L60; Jinken 1402, JK1402) were field-grown using three different topping treatments manual topping (MT), no topping (NT) and chemical topping (DPC+ and DPC) in irrigated arid lands of Xinjiang for two years. The plant height decreased by 1.4–13.6% for the DPC+ and DPC treatments compared with the NT treatment and increased by 3.8 –9.2% compared with the MT treatment. The thickness of the leaves, palisade tissue (Pt) and spongy tissue (St) increased by 5.1–21.5% under DPC treatment compared with other treatments. The 3-indoleacetic acid (IAA) content of the leaves significantly increased by 25.0–93.8% at 10 days under the DPC treatment compared with that under the MT and NT treatments. The zeatin riboside (ZR) content of the leaves and apical buds increased up to 7.5 times at 40 days under the DPC+ and DPC treatments compared with that under the NT treatment. The accumulation of reproductive organ biomass and proportion of reproductive organ dry matter to total dry matter under the DPC+ and DPC treatments increased by 2.0–39.7% compared with that under the MT and NT treatments. The seed cotton yield between the DPC+ and DPC treatments showed no significant difference. However, the seed cotton yield of JK1402 under the DPC+ and DPC treatments significantly increased by 9.5–11.7% compared with that under the MT and NT treatments. The main stem length was significantly correlated with the stem length of the upper part and gibberellin (GA) content in the apical buds. The leaf Pt and ZR contents were significantly correlated with the boll weight and seed cotton yield. Collectively, the data suggest that improved morpho-physiological traits of the apical part, such as an increase in the IAA and GA contents in the apical buds, leaf Pt and ZR contents, and boll weight, inhibited growth of the main stem and increased seed cotton yield for DPC, which is cheaper than DPC+ as a chemical inhibitor under chemical regulation during the whole growth period. • Chemical topping delays growth of the upper main stem. • Chemical topping enhances thickness and ZR contents of leaves. • DPC can increase boll weight and seed cotton yield in DPC-sensitive varieties. • DPC has the potential to replace manual and other chemical topping agents. [ABSTRACT FROM AUTHOR]

Background: Optimizing biochar application is vital for enhancing crop production and ensuring sustainable agricultural production. A 3-year field experiment was established to explore the effects of varying the biochar application rate (BAR) on crop growth, quality, productivity and yields. BAR was set at 0, 10, 50 and 100 t ha -1 in 2018; 0, 10, 25, 50 and 100 t ha -1 in 2019; and 0, 10, 25 and 30 t ha -1 in 2020. Crop quality and growth status and production were evaluated using the dynamic technique for order preference by similarity to ideal solution with the entropy weighted method (DTOPSIS-EW), principal component analysis (PCA), membership function analysis (MFA), gray relation analysis (GRA) and the fuzzy Borda combination evaluation method., Results: Low-dose BAR (≤ 25 t ha -1 for cotton; ≤ 50 t ha -1 for sugar beet) effectively increased biomass, plant height, leaf area index (LAI), water and fertility (N, P and K) productivities, and yield. Biochar application increased the salt absorption and sugar content in sugar beet, with the most notable increases being 116.45% and 20.35%, respectively. Conversely, BAR had no significant effect on cotton fiber quality. The GRA method was the most appropriate for assessing crop growth and quality. The most indicative parameters for reflecting cotton and sugarbeet growth and quality status were biomass and LAI. The 10 t ha -1 BAR consistently produced the highest scores and was the most economically viable option, as evaluated by DTOPSIS-EW., Conclusion: The optimal biochar application strategy for improving cotton and sugar beet cultivation in Xinjiang, China, is 10 t ha -1 biochar applied continuously. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)