Regulation Of Both Nitrogen And DPC On The Yield And Agronomic Triats For Direct Seeding Cotton After Wheat Harvest

In order to explore the interaction effect of both nitrogen and DPC(Dimethyl piperidiniumchloride)on yield composition,nitrogen absorption and utilization,plant type,and physiological characteristics for direct seeding cotton after wheat harvest,the study was conducted at cotton growing seasons of Yangzhou University Experimental Farm in 2019-2020.The main results were as follows:Under high-density planting,112.5kg/hm2 N combined with 180g/hm2 DPC was beneficial to the yield formation and concentrated boll setting for direct seeding cotton after wheat harvest.The seed cotton yields were at 4635.7 to 5329.2 kg/hm2;the lint yields were at 1684.7 to 2098.6 kg/hm2.Yield composition parameters further indicated that the increased yield was a result of increased both boll number and boll weight.Both the square and boll setting rates were also high,the values were 11.43 to 11.48 ten thousand hm-2d-1,and 2.48 to 3.27 ten thousand hm-2d-1,respectively.The dly matter accumulation of the reproductive organ was also high,which was at 4248.8 to 5980.8 kg/hm2;Population fruiting nodes nuumber was at 361.5-435.6 ten thousand hm-2.Therefore,the coordinated application of both optimum nitrogen and DPC would contribute to high yield and concentrated boll setting for direct seeding cotton after wheat harvest.Under high-density planting,the 112.5kg/hm2N combined with 180g/hm2 DPC resulted in high nitrogen accumulation in reproductive organs,which reached 1000.47 to 105.5kg/hm2,the nitrogen agricultural recovery efficiency(NARE)was at 54.26 to58.33%,the nitrogen partial factor productivity(PFP)was at 45.41 kg/kgN.the nitrogen agronomic efficiency(NAE)and the physiological efficiency(PE)utilization rate were also high.The enhanced nitrogen above 112.5kg/hm2 not only decreased the yield,but also decreased NARE,PFP,NAE and PE.Regression analysis further showed that t downward parabolic relationships were detected between the accumulation of nitrogen of vegetative organs and seed cotton yield,boll setting rate respectively;significant linear positive correlation were observed between nitrogen accumulation of reproductive organs and NAE,PE respectively.Therefore,the optimum application of both nitrogen and DPC under high-density planting promoted the nitrogen absorption and utilization for direct seeding cotton after wheat harvest,which provided the theory and practical basis for high yield,high efficiency,and reduced nitrogen application.the nitrogen application rate of 112.5kg/hm2 combined with 180g/hm2 DPC under high-density planting benefited to construct a high-photosynthetic-efficiency plant type,which were at 64.4 to 77.67 cm for plant heights;at 14.35 to19.7 cm,12.55 to14.32 cm,2.01-3.78 cm for fruiting branch lengths of the lower,middle and upper respectively;were,at 2.4 to2.98 for the ratio of fruiting nodes to fruiting branches;at 4.53-4.58 cm,3.72-4.33 cm and 2.23-2.29 cm for the main stem internode length of lower,middle and upper respectively;at 4.25-4,88 cm,3.00-4.25 cm and 1.99-2.41cm for the fruiting node internode length of lower,middle and upper respectively;at the7.8-8.38 mm,5.75-6.33 mm and 4.21-4.30 mm for main stem diameter of the lower,middle and upper respectively;at 36.4 to 54.8 for fruit branch direction value.Regression analysis showed that downward parabolic relationships were detected between these the plant type parameters mentioned above and seed cotton yield,boll setting rate respectively.Therefore,the reasonable application of both nitrogen and DPC under high-density planting could built the high-efficiency plant types for direct seeding cotton after wheat harvest,which provided basis for the formation of high photosynthetic efficiency population.112.5kg/hm2 Nwith180g/hm2 DPC under high-density planting benefited to enhance the root activity,bleeding sap,and the content of ZR and IAA in the bleeding.chlorophyll content,the primary conversion efficiency of light energy,soluble sugar content,the free ammno acids and soluble protein content,GPT and GOT activities.Correlation analysis further indicated that significant linear positive correlations were detected between TTC reduction intensity and seed cotton yield,boll setting rate respectively;linear positive correlations above significance were also detected between the chlorophyll content,the primary conversion efficiency of light energy,soluble sugar content,free amino acid content,soluble protein content,GPT and GOT activity and seed cotton yield,boll setting rate respectively.Therefore,the reasonable application of both nitrogen and DPC improved root activity and the intensity of carbon and nitrogen metabolism for the cotton plants,which benefited to enhance the yield and achieve concentrated boll setting.