Effects of planting patterns on yield, quality, and defoliation in machine-harvested cotton

The aim of this study was to elucidate the effects of different machine-harvested cotton-planting patterns on defoliation, yield, and fiber quality in cotton and to provide support for improving the quality of machine-harvested cotton. In the 2015 and 2016 growing seasons, the Xinluzao 45(XLZ45) and Xinluzao 62(XLZ62) cultivars, which are primarily cultivated in northern Xinjiang, were used as study materials. Conventional wide-narrow row(WNR), wide and ultra-narrow row(UNR), wide-row spacing with high density(HWR), and wide-row spacing with low density(LWR) planting patterns were used to assess the effects of planting patterns on defoliation, yield, and fiber quality. Compared with WNR, the seed cotton yields were significantly decreased by 2.06–5.48% for UNR and by 2.50–6.99% for LWR, respectively. The main cause of reduced yield was a reduction in bolls per unit area. The variation in HWR yield was –1.07–1.07% with reduced bolls per unit area and increased boll weight, thus demonstrating stable production. In terms of fiber quality indicators, the planting patterns only showed significant effects on the micronaire value, with wide-row spacing patterns showing an increase in the micronaire values. The defoliation and boll-opening results showed that the number of leaves and dried leaves in HWR was the lowest among the four planting patterns. Prior to the application of defoliating agent and before machine-harvesting, the numbers of leaves per individual plant in HWR were decreased by 14.45 and 25.00% on average, respectively, compared with WNR, while the number of leaves per unit area was decreased by 27.44 and 36.21% on average, respectively. The rates of boll-opening and defoliation in HWR were the highest. Specifically, the boll-opening rate before defoliation and machine-harvesting in HWR was 44.54 and 5.94% higher on average than in WNR, while the defoliation rate prior to machine-harvesting was 3.45% higher on average than in WNR. The numbers of ineffective defoliated leaves and leaf trash in HWR were the lowest, decreased by 33.40 and 32.43%, respectively, compared with WNR. In conclusion, the HWR planting pattern is associated with a high and stable yield, does not affect fiber quality, promotes early maturation, and can effectively decrease the amount of leaf trash in machine-picked seed cotton, and thus its use is able to improve the quality of machine-harvested cotton.