施氮水平和打顶后涂抹NAA 对盐渍土壤上长绒棉铃脱落和产量的影响

为探讨减少盐碱地棉花铃脱落的途径, 田间条件下研究了土壤供应低氮(N 226.5 kg·hm^-2)和高氮(N 346.5 kg·hm^-2)条件下, 不打顶、打顶和打顶后涂抹生长素对棉花铃脱落和产量构成因素的影响。结果表明, 低氮和高氮水平下, 打顶、打顶后涂抹NAA 处理果枝落铃率都低于不打顶处理。打顶后涂抹浓度为0.3 mmol·L^-1 的NAA 处理在低氮水平下的成铃率比传统打顶处理高1.3 个百分点, 而铃脱落率比传统打顶处理低0.8 个百分点, 皮棉产量比传统打顶处理高23.7%。高氮水平下, 与传统打顶处理相比, 打顶后涂抹浓度为3 mmol·L^-1 的NAA 单株成铃率、铃脱落率、皮棉产量之间差异不显著。在同一处理中, 高氮水平的单株成铃数、单铃重和吐絮数均低于低氮水平, 而衣分无明显差异, 从而导致皮棉产量下降。上述结果说明, 打顶后涂抹一定浓度的NAA 可增加棉花单株现铃、成铃、吐絮数, 增加单铃重, 降低落铃率, 从而提高产量, 而过量施用氮肥会导致产量下降。

Effects of N application levels and post-decapitation smearing of NAA on fruit abscission and yield of cotton (Gossypium barbadense L.) in saline soil

A field experiment was conducted to investigate the effects of decapitation (a conventional cotton cultivation technique in Xinjiang) and smearing NAA after decapitation on the yield and fruit abscission of cotton under low (226.5 mg·kg^-1) and high (346.5 mg·kg^-1) nitrogen doses in a saline soil. The results showed that fruit abscission rates of decapitation and smearing with NAA after decapitation were lower than those of non-decapitation treatment under both low and high nitrogen levels. Compared with the conventional decapitation treatment, smearing with 0.3 mmol·L^-1 NAA after decapitation increased boll retention rate and cotton yield by 1.3% and 23.7%, respectively. It, however, decreased fruit abscission rate by 0.8%, under low nitrogen application. In terms of boll retention rate, fruit abscission rate and cotton yield under high nitrogen application, no significant difference was noted between smearing with 3 mmol·L^-1 NAA after decapitation and conventional decapitation practices. Boll retention rate, weight per boll and number of opened boll were lower under high nitrogen level than under low nitrogen level. Furthermore, ginning yield was not different between different nitrogen levels in the same decapitation treatment. Lint weight under low nitrogen level was higher than that under high nitrogen level. It was concluded that smearing cotton with proper concentrations of NAA after decapitation increased boll retention rate and decreased fruit abscission rate, which eventually enhanced cotton yield. Cotton yield decreased with excessive nitrogen application level.