Effect Of Reduced Nitrogen Fertilizer And Intercropping Green Manureon Ramie Yield

Ramie?Boehmeria nivea L.Gaudich.?is an environmental friendly cash crop in China,which has been dominated in international bast fiber market for a long time.Excessive nitrogen application is common in ramie cultivation in China.Nitrogen use efficiency is decreasing year by year,and the ecological environment is gradually deteriorating,which is not conducive to the sustainable development of ramie.Therefore,reducing nitrogen fertilizer and increasing efficiency is an important direction of future research.Planting green crops in the winter fallow field,then their harvesting and mixing as green manure into the soil in next spring is an effective approach to improve the fertility of agricultural lands.However,there is still a lack of systematic research on how many N fertilizer inputs can be reduced in actual production,and how to reduce the effect of N fertilizer on ramie production,and whether it can compensate for the loss of production by turning over Chinese milk vetch?In present study,ramie for fiber cv.“Huazhu No.5”was planted.The nitrogen fertilizer was applied at different rates viz.,100%,85%,70%,and 55%,and no nitrogen as control.Nitrogen fertilizer test was carried out under direct reduction of nitrogen fertilizers(denoted as N₁₀₀?N₈₅?N₇₀?N₅₅ and CK₁)and in the case of Chinese Milk Vetch(referred to as AN₁₀₀?AN₈₅?AN₇₀?AN₅₅ and CK₂).The effects of two methods of reducing N application on ramie yield,dry matter accumulation,nitrogen uptake and utilization,and soil fertility were studied.The main results are as follows:1.Effect of reduced nitrogen application on yield of ramieThe total yield of ramie first crop was increased and then decreased with the decrease in N application.However,the yield of ramie second and third crop was decreased with the decrease in N application,85%N fertilizer treatment showed highest yield.Compared with 100%N fertilizer treatment,85%N increased the plant height of the first and third crop and the effective plant efficiency of the third crop,thus increasing the total yield of Ramie by 1.33%.The dry matter accumulation of ramie was increased during first crop and then decreased with the decrease of N application.The dry matter accumulation of ramie at85%N was increased by 9.90%compared with that in 100%N fertilizer treatment.In addition 85%N also promoted dry matter accumulation in the above ground part of ramie.The accumulation of nitrogen in ramie increased during first crop and then decreased with the decrease in N application rate,and the total N accumulation at 85%N was the highest.85%N increased the N accumulation in the first and second crop by10.95%and 10.04%as compared to 100%N fertilizer treatment,While,70%N increased the nitrogen accumulation in the third crop by 31.94%that of 100%N fertilizer treatment.Compared with 100%N,70 and 85%N fertilizer treatment had higher N fertilizer use efficiency,N fertilizer agronomic use efficiency as well as partial N fertilizer productivity and N harvest index.Compared with control,the application of N fertilizer reduced the soil pH and increased the contents of available potassium,total nitrogen and organic matter.In comparison of 100%N fertilizer,reducing N application reduced the content of soil organic matter,available potassium and available phosphorus during first and second crop.However,the decrease of soil available phosphorus,total nitrogen,available potassium and organic matter at 85%N fertilizer treatment did not reach significant level.2.Effects of Chinese milk vetch application and reduced nitrogen fertilizer on ramie yieldWith Chinese milk vetch application,the yield of ramie was increased and then decreased with the decrease in N application.70 and 85%N fertilizer treatments increased the total yield of ramie.Compared with 100%N fertilizer treatment,the yield at 70 and 80%N fertilizer treatment were increased by 10.32%and 14.31%.The plant height of ramie was increased during first crop and then decreased with the decrease of nitrogen application.The effective plant rate during first crop at all levels of N fertilizer viz.,100%,85%,70%,55%was decreased with the decrease of N application,while during second and third crop it was increased initially,and then declined.With the application of Chinese milk vetch,the dry matter accumulation of ramie was increased during the first crop and then declined with the reduction of N application.Compared with 100%N,the dry matter accumulation of first,third and the whole year crop was increased by 85 and 70%N fertilizer treatments however during second crop it was increased by 85%N fertilizer treatment only.With Chinese milk vetch application,the dry matter accumulation at 70%N was 23.25%higher than that of 100%N fertilizer treatment.With Chinese milk vetch application,reducing N fertilizer application reduced the nitrogen accumulation during second crop,but the nitrogen accumulation during first and third crops showed a parabola trend.Compared with 100%N,the total nitrogen accumulation of ramie was increased by 5.20%¹5.11%by reducing 15%³0%nitrogen fertilizers,respectively.70%N significantly improved the nitrogen use efficiency,agronomic use efficiency,partial productivity of nitrogen fertilizer and nitrogen harvest index as compared to 100%N fertilizer treatment.With Chinese milk vetch application,compared with the control,the application of N fertilizer decreased the soil pH and increased the contents of organic matter,available phosphorus and available potassium.Nitrogen fertilizer treatments had different effects on soil nutrients at different growth stages.With the decrease in N application,the contents of soil available phosphorus and potassium during first crop were decreased gradually,while the contents of available phosphorus in the second and third crops were increased first and then decreased.The content of soil available phosphorus,total nitrogen,available potassium and organic matter did not decrease significantly by 15%³0%nitrogen reductions.In summary,application of N fertilizer and Chinese milk vetch can alleviate soil acidification.Highest ramie yield?1643.16 kg/hm²?and economic benefits?22529.8yuan/hm²?were obtained at 70%N fertilizer treatment.It improved the utilization rate of N fertilizer and was beneficial towards sustainable development of ramie.In the model of direct reduction of N fertilizer application,85%N fertilizer treatment improved the utilization rate of N fertilizer,and its yield and economic benefits were the best,1673.94kg/hm² and 23354.3 yuan/hm²,respectively,which could provide reference for rational fertilization of ramie.