Effects Of Density And DPC On Cotton Growth And Yield Under The Planting Mode Of One Film With Three Rows In Southern Xinjiang

Planting density and 1,1-dimethyl piperidinium chloride（DPC）dosage are the most importantcotton growing practices which play a vital role in cotton production.To explore the optimalcombination of planting density and DPC dosage of cotton,the current research investigated the effects of planting density,DPC dosage and planting density by DPC dosage interaction onagronomic traits,biomass and seed cotton yield under a condition of growing three rows on one plastic mulch.The experiment was conducted at Xinjiang Alaer Trial Station of Institute of Cotton Research institute of Chinese Academy of Agricultural Sciences in 2018-2019.The test material is zhongmiansuo 49,with split-plot experiment design,and the planting density was mainly treated with three levels,namely,94,000,141,000 and 188,000 plants per hm².The dosage of DPC was set as a secondary treatment with three levels of 90 g·hm^-2,180g·hm^-2 and 270g·hm^-2.Agronomic traits,biomass and seed cotton yield were assessed under all treatment levels.The results were as follows:1.Effects of planting density and amount of amine on agronomic characters of cottonPlanting density by DPC dosage interaction significantly affected plant height,stem diameter and internode length,while had small effect on growth period,fruit branch number and first fruitbranch position.After the flowering period,the differences among the treatments were gradually significant.Under the same density level,plant height and inter-node length decreased while stem diameter increased as the dosage of DCP was increased.Under the same DCP level,plantingdensity was positively correlated with plant height and negatively correlated with stem thickness,and inter-node length increased in early growth stage and then decreased with the increasing of density.Under 188,000 plants per hm² density and 90g·hm^-22 DPC dosage,the plant height ofcotton was the highest with a value of 82.9 cm and 76.4 cm in 2018 and 2019,respectively.The stem thickness showed the maximum value Under 94,000 plants per hm² density and 270g·hm^-2DPC dosage,which were 12.9 mm and 14.8 mm in 2018 and 2019,respectively.2.Effects of planting density and high DPC dosage on cotton biomass accumulation and photosynthetic traitsThe proportion of vegetative organs（roots,stem and leaves）in the whole plant decreased while the proportion of reproductive organs（buds,flowers and bolls）increased with the advancement of the growth process.At the later growth stage there was no significant biomass accumulationdifference in the reproductive organs between treatments,and the biomass accumulation reached the highest at the density of 94,000 plants per hm² with a DPC dosage of 180 g·hm^-2,3764.27kg·hm^-22 and 4055.16 kg·hm^-2 in 2018 and 2019,respectively.Leaf area index（LAI）of cotton is a comprehensive index of light utilization efficiency and canopy structure of cotton plants.Two-way ANOVA showed that planting density and DPC dosage hadsignificant effects on LAI of cotton,and the interaction effect between the two factors existed.At the squaring stage,LAI decreased with the increase of DPC concentration.planting density while LAI increased with the increasing of planting density under the same DPC level.As growthproceeded,LAI continued to increase under low planting density condition,while medium and high density LAI decreased after reaching the peak in the flowering period.LAI value was the highest when the density was 141,000 plants per hm² with a DPC dosage of 180 g·hm^-2.Planting density had no significant effect on SPAD in cotton,while the concentration of chlorophyllincreased with the increasing of DPC dosage.Planting density had a significant effect on the photosynthesis,while the effect of DPC dosage was small with non-significant effect between treatments.3.Effects of planting density and high DPC dosage on seed cotton yield and qualitySeed cotton yield formation is closely related to the regulation of planting density and DPC dosage.Two-way ANOVA results indicated that planting density and DPC dosage and the interaction between them had significant effects on seed cotton yield.Under the same planting density or DPC dosage level,seed cotton yield showed a trend of rising first and falling later as treating level increased.Seed cotton yield was the highest when the density was 141,000 plants、per hm² with a DPC dosage of 180 g·hm^-2,reaching 6135 kg·hm^-2 and 5184 kg·hm^-2 in 2018 and2019,respectively.No significant effect on the quality of cotton fiber was detected.