种植密度和缩节胺调控对麦后直播棉产量和冠层特征的影响

2013―2014年以早熟棉(中棉所50)为材料,采用裂区设计,在江苏省南京市研究了种植密度(7.50万、9.75万和12.00万株·hm~(-2))和缩节胺(DPC)调控(0,52.5和105.0 g·hm~(-2))对麦后直播棉产量和冠层特征的影响。结果表明:皮棉产量在不同种植密度下以12.00万株·hm~(-2)处理最低,在不同DPC用量水平下以0 g·hm~(-2)处理最低;种植密度与DPC调控存在互作效应,以种植密度9.75万株·hm~(-2)、DPC用量52.5~105 g·hm~(-2)处理产量较高,且产量构成中以铃数对产量的直接效应最大。对冠层特征影响表明,下部果枝夹角和长度随种植密度增加而降低,而中、上部果枝的夹角和长度、叶面积指数均以种植密度9.75万株·hm~(-2)处理较高;不同部位果枝夹角和长度、叶面积指数均随DPC用量增加而降低,而透光率则相反。相关分析表明,下部果枝夹角大、中部果枝较长及上部果枝夹角小且叶面积指数和透光率较高,有利于提高产量和霜前花率。综上,该棉区麦后直播棉种植密度9.75万株·hm~(-2)、DPC用量52.5~105 g·hm~(-2)(蕾期、开花期和打顶后用量比例为1∶2∶4),有利于改善棉花冠层特征,实现早熟高产。

Effects of Planting Density and Growth Regulator Mepiquat Chloride on Yields and Canopy Architecture of Cotton Sown after Harvesting Barley

Using the early mature cotton (CCRI 50) as material, a field experiment was carried out to evaluate the effects of the plant growth regulator mepiquat chloride (DPC) on yield and canopy architecture of cotton sown after harvesting barley in Nanjing, Jiangsu Province, China, in 2013―2014. A split-plot design with three replicates was used for the study. The main plots comprised three planting densities (7.5 × 10⁴, 9.75 × 10⁴, and 12 × 10⁴ plant·hm^－2), while different DPC application rates (0, 52.5, and 105 g·hm^－2) constituted the subplots. The results showed that the lowest lint yields were found at the planting density of 12 × 10⁴ plant·hm^－2 and the DPC addition rate of 0 g·hm^－2, respectively. A significant interaction was detected between planting density and DPC on lint yield and as a result, the treatment of 9.75 × 10⁴ plant·hm^－2 with DPC of 52.5―105 g·hm^－2 achieved higher lint yield than other treatments. The boll number of yield component has the largest direct effect on lint yield. In terms of canopy architecture, the angles and length of low fruit branches decreased with planting density increase, while the larger angles, length, and leaf area index of middle and upper fruit branches were found at 9.75 × 10⁴ plant·hm^－2. The angles and length of fruit branches and the leaf area index decreased with the DPC application rate increase but the opposite was observed for the transmittance. The correlation analysis between the canopy characteristics and lint yield indicated that it was conducive to increase the yield and seed cotton rate before frost for plants with larger angles at the low fruit branch, longer length of the middle fruit branch, and smaller angles at the upper fruit branch with a higher leaf area index and transmittance. In summary, cottonsown after harvesting barley at a planting density of 9.75 × 10⁴ plant·hm^－2 with DPC of 52.5―105 g·hm^－2, which was applied at the ratio of 1∶2∶4 at the budding stage, flowering stage, and after topping, could improve canopy architectures, thus increasing earliness and yield of cotton in the lower reaches of the Yangtze River.