Effects Of DPC On Cotton Yield And Quality At Different Densities

Plant density and DPC are two important practices for field-grown cotton(Gossypium hirsutum L),which have great effects on seed cotton yield and fiber quality.Field experiments were carried out in in 2013 and 2014 in Dafeng Experimental Station in Dafeng(33°24'N and 120°34'E),Jiangsu Province,China.A split-plot design with three replications was used for this study.The main plot treatments were 135 g ha-1 of DPC and an untreated control,while plant densities of 1.35,2.55,3.75 and 4.95 plants m-2 were assigned to the subplot treatments,respectively.Two cotton cultivars,Siza 3 and Sikang 1 were used in the experiment.We investigated DPC on cotton yield,biomass accumulation,nutrient uptake and carbohydrate distribution at different densities.The main results were as follows:1.Effect of DPC on cotton yield,quality and biomass accumulation at different densitiesThere were significant interaction effects of variety,DPC and planting density on seed cotton yield,micronaire,fiber uniformity and cotton plant biomass.Increasing the planting density increased the number of bolls per unit area and the seed cotton yield,and reduced the boll weight.Compared to the untreated control,boll weight and seed cotton yield were increased by applying DPC.Increading plant density without DPC reduced fiber length,fiber strength and uniformity,and increading plant density with DPC improved fiber length,fiber strength and uniformity.DPC reduced plant biomass and improved the seed cotton harvest index.2.Effect of DPC on uptake and distribution of N,P and K at different densitiesUnder the conditions of plant density and DPC,the cumulative process of uptake of N,P and K in cotton plants met Logistic growth curve.Increasing plant density increased accumulation of N,P and K in cotton plants.The maximum of rate N,P accumulation increased with the increasing of plant density,and the maximum of rate K accumulation and theoretical K accumulation decreased when plant density were increased.Application of DPC extended the period of rapid N accumulation,reduced the maximum of rate N accumulation.The highest maximum of rate N accumulation and N theoretical accumulates of sikang 1 were obtained at 3.75 plants m-2,while siza 3 were obtained at 4.95 plnat m-2.3.Effect of DPC on cotton carbohydrate accumulation and distribution at different densitiesIncreasing plant density reduced soluble sugar,sucrose,starch content of stem and sucrose content of leaves.The content of soluble sugar and starch of leaves increased when plant density was increased.The accumulation and output capacity of carbohydrates decreased when plant density was increased.Increasing plant density without DPC decreased soluble sugar,sucrose,and starch content in bolls,while increasing plant density with DPC increased soluble sugar,sucrose content in bolls and decreased starch content in bolls.