Regulation Effects Of Polyaspartic Acid(PASP)on Nitrogen Metabolism And Its Mechanism Of Nitrogen Saving Of Spring Maize In The Northeast China

Polyaspartic acid has the function of chelating and adsorbing positive and negative ions and can enrich nutrients.However,the one-time application of conventional nitrogen fertilizer will lead to surplus nitrogen in the early stage and defertilizer in the later stage,which is not conducive to the growth and development of crops and the efficient utilization of nitrogen.Randomized block field experiments were conducted using variety of Zhongdan 909 in the Institute of Crop Sciences,the Chinese Academy of Agricultural Sciences,Gongzhuling,Jilin province in 2017 and 2018 to explore the effects of PASP on spring maize plant morphological development,dry matter accumulation and distribution,yield and yield components,key nitrogen metabolism enzyme activity of leaf,nitrogen accumulation and changes of available nitrogen in soil by setting one-time application of no nitrogen?CK?treatment,different nitrogen application rates(75.0,112.5,150.0,225.0 kg ha^-1)of conventional fertilizer?CN?and PASP chelating nitrogen fertilizer?PN?treatments,which aims to study the regulation effects of PASP on nitrogen metabolism of spring maize in northeast China and the one-time application synergistic mechanism of PASP chelating nitrogen fertilizer from the point of morphological development and nitrogen metabolism.The research results are as follows:PASP chelating nitrogen treatments improved the morphological development,dry matter accumulation and distribution of maize plant,yield components and increased the yield.The research showed that both CN and PN treatments were able to increase grain yield,which was 57.8%⁸3.2%and63.6%⁸3.7%higher than CK,respectively;PN treatments increased yield by 3.3%⁶.8%on average compared to CN treatments.Curve simulation of nitrogen application rates and yields showed that the yield showed a trend of rising at first and then falling with the increase of nitrogen application rates.While the maximum yield was reached,the nitrogen application rates of PN treatment was lower than that of CN treatment,and when the N application rates was lower than 152.2 kg ha^-1,the nitrogen application rates of PN treatment was significantly lower than that of CN treatment with the same yield.Compared with CN,PN treatments could increase ear diameter,1000-grain weight,dry matter accumulation,and grain volume during grain filling period.As a consequence,PASP can promote the accumulation and partitioning of dry matter,thus increase the 1000-grain weight and the yield of maize.PASP chelating nitrogen treatments increased the activity of key enzymes of nitrogen metabolism and promoted the absorption and utilization of nitrogen.The research showed that CN and PN treatments were able to increase the activity of nitrogen-metabolization-related enzymes comparing to CK.Compared with CN treatments,PN treatments were capable to increase NR,GPT and protease activity,soluble protein and free amino acid content.PASP could promote nitrogen absorption,partitioning and utilization.Compared with CK,CN and PN treatments could increase the contents of NH₄⁺-N and NO₃^--N in the wound fluid.Compared with CN,PN treatments could increase NO₃^--N content and thus promote nitrogen absorption and utilization.PASP chelating nitrogen treatments increased the available nitrogen content in surface soil and promoted the uptake and utilization of nitrogen by plants.The research showed that CN and PN treatments were able to increase the contents of NO₃^--N and NH₄⁺-N in soil.Compared with CK,CN and PN treatments could increase the contents of NO₃^--N of soil layer of 0⁶0 cm in V6,VT and R6,and the contents of NH₄⁺-N in soil layer of 0⁶0 cm in VT and VT+30.Compared with CN,PN treatments were capable to increase the contents of NO₃^--N and NH₄⁺-N in soil layer of 0⁶0 cm,improve the soil nitrogen effectiveness of 0⁶0 cm,and promote the utilization of available nitrogen.PASP chelating nitrogen treatments increased nitrogen utilization efficiency.The research showed that CN and PN treatments were able to increase nitrogen accumulation and nitrogen utilization efficiency in plants.PN treatments improved the nitrogen accumulation of plants,the apparent N utilization rate,agronomic efficiency and partial N productivity comparing to CN treatments.PASP chelating nitrogen treatments had the effects of reducing nitrogen application rates and stabilizing yield.The research showed that compared with CN treatments,PN treatments reducing nitrogen by 1/3 could increase the dry matter accumulation after anthesis,which can maintain and even increase the yield of maize,in the meanwhile improve the agronomic N efficiency,partial N productivity and apparent N utilization rate.PASP chelating nitrogen fertilizer is capable to be applied in the spring corn area of northeast China with reducing nitrogen by 1/3.