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In order to study the effects of different irrigation amounts on the root characteristics and yield of cotton without film mulching (abbreviated as filmless cotton) under drip irrigation in Southern Xinjiang, five irrigation amounts of filmless cotton (300, 375, 450, 525 and 600 mm, represented by W1, W2, W3, W4 and W5) and one irrigation amount of cotton with film mulching (abbreviated as filmed cotton) (450 mm, represented by WCK) were set. The effects of irrigation amount on root length density (RLD), root surface area (RSA), root average diameter (RAD), root volume (RV), root weight density (RED) and yield of filmless cotton were analyzed. The results of the two-year experiment showed the following: (1) The indexes of cotton root growth reached the maximum at the flowering and bolling stage, and the growth of soil root in the periphery (30 cm from the main root) and the lower layer (40–60 cm soil layer) reached the peak at the flowering and bolling stages, respectively; (2) The average value of root growth index of film-free cotton in each treatment was W2 > W3 > W4 > W5 and W1. The RLD of W2 and W3 increased by 19.41–106.67% and 13.66–84.22% in the peripheral and lower soil layer, and the proportion of RSA in the peripheral and middle soil layer (20–40 cm soil layer) increased by 1.64–3.41% and 0.49–4.09% compared with other treatments. The RAD, RV and RWD after W2 treatment were relatively large at various distribution points in the soil, followed by W3 treatment; (3) The average root indexes of WCK were not significantly different from those of W3, but the indexes of the lower soil layer were the smallest, at only 29.18–66.84% of the average value of the non-film mulching treatment, while the root indexes of the surface layer (0–20 cm soil layer) and the surrounding soil were larger, with an increase of 11.43–102.17% and 29.60–111.57%, respectively, compared with the non-film mulching treatment; (4) The seed cotton yield of W3 was the highest in the non-film mulching treatment, reaching 4833.25 kg·hm−2, but was still lower than that of WCK by 27.79%. Conclusion: An appropriate water deficit is conducive to root growth and increases the uniformity of its distribution in the soil layer. The irrigation amount of 375–450 mm for filmless cotton in Southern Xinjiang can promote root growth, prevent senescence and increase yield, which can be used as a reference in production. [ABSTRACT FROM AUTHOR]

In order to resolve the problems of of time-consuming, inefficient and high cost of artificial top-sealing in cotton production process, the interplay effect of planting density and capping on cotton yield and fiber quality was explored, and the feasibility of replacing the artificial seal with chemical seal was analyzed. As one of the techniques of mechanized and simplified cultivation of cotton, chemical topping has certain influence on the growth and yield formation of different populations of cotton. In this paper, 419 was used as the material for the split plot experiment. The density was the main area including 9x104 plants/hm², 18xl04 plants/hm² and 27x 104 plants/hm² ; the topping mode was the sub-area including no-topping, artificial topping and chemical topping. The effects of different topping methods under different planting densities were studied, and the feasibility of chemical topping instead of artificial capping was also discussed. The results showed that: Under the same topping method, the translocation rate of reproductive organ dry weight and LAI increased with the increase of density, but the leaf area, dry matter accumulation and harvest index decreased, and the plant height changed little. Under the same density, topping method had little effect on leaf area per plant, LAI and dry matter accumulation per plant. Compared with the no- topping treatment, the plant height of topping treatment was reduced by 4. 90 ~ 6.46 cm, and the dry matter translocation rate of reproductive organs, harvest index, lint content and yield were increased by 6.33 ~ 9.47 percentage points, 0.03 ~ 0.05 percentage points, 0. 03 ~ 1.01 percentage points and 529. 56 ~ 301.42 kg/hm², respectively; Compared with artificial topping, though the leaf area, LAI, plant height and dry weight per plant of chemical topping treatment were increased by 0.01 m², 0.11, 1.56 cm and 1.80 g/plant, respectively, the dry matter transport rate, harvest index, lint percentage and yield were decreased by 3.14 percentage points, 0.03, 0.42 percentage points and 228.14 kg/hm², respectively; but there was no significant difference among the characters. The interaction between density and topping method is less affected. The above showed that topping was the key measure to optimize cotton growth and ensure yield, and chemical topping had the similar effect of artificial topping. [ABSTRACT FROM AUTHOR]