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To optimize the spatial distribution of cotton bolls and to increase the yield, the relationship between yield components and boll spatial distribution was investigated among different Bt (Bacillus thuringensis) cotton varieties. A five-year field experiment was conducted to reveal the reasons for the differences in lint yield and fiber quality across three Bt cotton varieties with different yield formations from 2013 to 2017. The lint yield of Jiman 169 (the average yield from 2013–2017 was 42.2 g/plant) was the highest, i.e., 16.3 and 36.9% higher than Lumianyan 21 (L21) and Daizimian 99B (99B), respectively. And the differences in boll weight among the three cultivars were similar to the lint yield, while the others yield components were not. So the increase in lint yield was mainly attributed to the enlargement in boll weight. However, the change in fiber quality was inconsistent with the lint yield, and the quality of L21 was significantly better than that of Jimian 169 (J169) and 99B, which was caused by the diversity of boll spatial distribution. Compared with 99B, the loose-type J169 had the highest number of large bolls in inner positions; the tight-type L21 had a few large bolls and the highest number of lower and middle bolls. And approximately 80.72% of the lint yield was concentrated on the inner nodes in Jiman 169, compared with 77.44% of L21 and 66.73% of 99B during the five-year experiment. Although lint yield was significantly affected by the interannual changes, the lint yield of J169 was the highest and the most stable, as well as its yield components. These observations demonstrated the increase in lint yield was due to the increase in boll weight, and the large bolls and high fiber quality were attributed to the optimal distribution of bolls within the canopies.

Stubble return is a proposed practice for soil amelioration and yield improvement. However, from the perspective of reducing soil salinity and improving soil nutrient availability, we have little knowledge of the effect of successive stubble return on cotton yield and nutrient uptake when cotton stubble is incorporated into saline field soil. Hence, a 5-year field study was conducted to investigate the effects of successive stubble management (stubble return and stubble removal) on lint yield and nutrient uptake of cotton, soil nutrients and salinity in the 0–80-cm soil profile. Stubble return increased lint yield by 22.7% and 47.3% in the fourth and fifth year, respectively, mainly through the production of more and larger bolls and the acquisition of more nutrients compared with stubble removal. 5-year cotton stubble return produced 20.0% more bolls and 7.7% larger bolls than stubble removal. Cotton plants accumulated 58.9% more nitrogen (N), 54.5% more phosphorus (P), and 48.2% more potassium (K) under stubble return than stubble removal during the last two years of the experiment. Stubble return increased internal N use efficiency (iNUE) and internal K use efficiency (iKUE) at the fourth or fifth year compared with stubble removal, without influence on internal P use efficiency (iPUE). Stubble return decreased soil pH and salinity in the 0–40-cm soil layer in the fourth and fifth year. The soil nitrate content below the 40-cm soil layer was reduced, while the nitrate concentration in the 0–20-cm soil layer increased after 4 years of stubble return. Available K in the 0–40-cm soil layer increased, while available P in the 0–20-cm soil layer was reduced after 5 years of stubble return. Our analyses demonstrate that cotton stubble return has the potential to improve cotton yield and may be an effective practice to apply in coastal saline areas.

To clarify the effects of cotton straw returning on the composition and contents of nu-trients in different particle sizes of aggregates, two treatments with or without cotton straw returning were tested in continuous three years. After three years straw treatments, we collected undisturbed soil within 0-5, 5-10, 10-20 and 20-30 cm soil layers, and to measure the composition, soil organic carbon, nitrogen, phosphorus and potassium contents in different particle sizes of aggregates classified using dry sieving. Returning cotton straw into the field significantly increased particle contents of 2-5 mm and5 mm aggregates in 0-5 cm soil layer, while the content of0.25 mm micro-aggregates was decreased. Cotton straw returning significantly improved soil organic carbon, nitrogen, and potassium contents by 19.2%, 14.2% and 17.3%, respectively, compared to no returning control. In 5-10 cm soil layer, cotton straw returning increased the contents of 2-5 mm and5 mm aggregates, reduced the content of0.25 mm micro-aggregate, but significantly increased contents of soil organic carbon, available nitrogen and potassium by 19.6%, 12.6% and 23.4%, compared to no straw returning control. In 10-20 cm soil layer, cotton straw returning significantly reduced the content of0.25 mm micro-aggregates, and significantly enhanced soil organic carbon, nitrogen, and potassium contents by 8.4%, 10.9% and 11.5%, compared to the control. However, in 20-30 cm soil layer, cotton straw returning only increased soil available potassium content by 12.0%, while there were no significant changes in particle size, organic carbon, nitrogen and phosphorus contents. We concluded that cotton straw returning could significantly improve the structure of surface soil by increasing the number of macro-aggregates, contents of organic carbon, available nitrogen and potassium in aggregates, while decreasing micro-aggregate content. The enhancement of the contribution of macro-aggregates to soil fertility by returning cotton straw could improve soil physical structure, fertility and then increase cotton yield.试验设置棉花秸秆还田和不还田两个处理,还田年限为3年.于第3年11月采集0～5、5～10、10～20和20～30 cm的原状土,采用干筛法将土壤团粒结构分级,研究棉花秸秆还田对土壤团聚体组成和不同粒径土壤团聚体中有机碳和速效氮、磷、钾含量的影响.结果表明: 在0～5 cm土层,棉花秸秆还田显著提高了5和5～2 mm团聚体含量,显著降低了0.25 mm微团聚体含量;团聚体有机碳、碱解氮和速效钾含量显著提高,平均提高幅度分别为19.2%、14.2%和17.3%.在5～10 cm土层中,棉花秸秆还田显著提高了5和5～2 mm团聚体含量,显著降低了0.25 mm微团聚体含量;团聚体有机碳、碱解氮和速效钾显著提高,平均提高幅度分别为19.6%、12.6%和23.4%.在10～20 cm土层中,棉花秸秆还田显著降低了0.25 mm微团聚体含量;团聚体有机碳、碱解氮和速效钾含量显著提高,平均提高幅度分别为8.4%、10.9%和11.5%.在20～30 cm土层中,棉花秸秆还田仅显著提高了团聚体速效钾含量,比对照提高了12.0%.棉花秸秆还田显著提高了0～5、5～10 cm土层5和2～5 mm团聚体各养分贡献率及0.25～0.5 mm团聚体有机碳、碱解氮贡献率,显著降低了0.25 mm微团聚体各养分贡献率.棉花秸秆还田能增加大团聚体百分含量,降低微团聚体百分含量;显著提高各粒径土壤团聚体中有机碳、碱解氮和速效钾的含量,对速效磷含量无显著影响;提高了大团聚体对土壤养分的贡献率,有利于土壤结构及其养分状况的改善和棉花籽棉、皮棉产量的提高.

Background. Inflammation might play a crucial role in the pathogenesis of osteoarthritis (OA). Interleukin-34 (IL-34) is a well-known proinflammatory cytokine. Objective. The objective of this study was to detect IL-34 levels in serum and synovial fluid (SF) of patients with OA and to investigate their correlation with radiographic and symptomatic severity. Methods. One hundred and eighty-two OA patients and 69 controls were recruited. IL-34 levels were measured by enzyme-linked immunosorbent assay (ELISA). Radiographic and symptomatic severity of OA was reflected by Kellgren-Lawrence (KL) grades and Western Ontario McMaster University Osteoarthritis Index (WOMAC) scores, respectively. Results. SF IL-34 levels were independently associated with the KL grade (B=0.273, 95% CI: 0.150–0.395; P<0.001). SF IL-34 levels were significantly correlated with WOMAC scores (r=0.265, 95% CI: 0.123–0.399; P<0.001). The correlation between SF IL-34 levels and WOMAC scores was still significant after adjusting for confounding factors (B=0.020, 95% CI: 0.001–0.038; P=0.035) in OA patients. Conclusions. We found that IL-34 levels in SF were significantly associated with the radiographic and symptomatic severity of knee OA.