Effects Of Carbon And Nitrogen Addition On Soil Organic Nitrogen Components And Availability In Dry Farmland

In order to investigate the effects of carbon and nitrogen addition on soil acidification organic nitrogen components in Dryland farmland of Longzhong Loess Plateau,this study relied on the carbon and nitrogen addition location experiment of Gansu Agricultural University in Lijiabao Town,Anding District,Dingxi City,in 2014.(9 treatments,no carbon+pure nitrogen 0 kg·hm^-2?CN0?,no carbon+pure nitrogen 50 kg·hm^-2?CN50?,no carbon+pure nitrogen 100 kg·hm^-2?CN100?;biochar 15 t·hm^-2+pure nitrogen 0 kg·hm^-2?BN0?,biochar 15t·hm^-2+pure nitrogen 50 kg·hm^-2?BN50?,biochar 15 t·hm^-2+pure nitrogen 100 kg·hm^-2?BN100?;straw 4.5 t·hm^-2+pure nitrogen 0 kg·hm^-2?SN0?,straw 4.5 t·hm^-2+pure nitrogen 50kg·hm^-2?SN50?,straw 4.5 t·hm^-2+pure nitrogen 100 kg·hm^-2?SN100?.Bremner classification method was used to determine and analyze the soil organic nitrogen components,soil total nitrogen,nitrogen accumulation in different organs of wheat plant and wheat yield after harvest in 2018.The purpose of this study was to explore the effects of carbon and nitrogen addition on soil organic nitrogen content,distribution characteristics and nitrogen supply potential,to provide rational fertilization methods for sustainable agricultural development,environmental friendliness and improvement of soil fertility and vitality,and to provide theoretical basis for nitrogen cycle,balance and restriction in Dryland farmland ecosystem.The results show that:1.Soil acidolysis total nitrogen,acidolysis ammonia nitrogen,acidolysis amino acid nitrogen,acidolysis unknown nitrogen and non-acidolysis nitrogen decreased with the deepening of soil layer,while the content of acidolysis amino sugar nitrogen increased with the deepening of soil layer.In 0-30 cm soil layer,the distribution of various forms of soil organic nitrogen showed non-acidolysis nitrogen>acidolysis amino acid nitrogen.>The trend of acidolysis of ammonia nitrogen>acidolysis of unknown nitrogen>acidolysis of aminosaccharide nitrogen.2.Nitrogen application?mean values of CN100,SN100 and BN100?,straw addition?mean values of SN0,SN50 and SN100?and biomass carbon addition?mean values of BN0,BN50and BN100?could significantly increase the contents of total organic nitrogen,acid hydrolyzed amino acid nitrogen,acid hydrolyzed ammonia nitrogen,acid hydrolyzed amino sugar nitrogen and their proportion in total nitrogen,among which nitrogen addition had the most significant effect on the increase of acid hydrolyzed amino acid nitrogen.The effect of biomass charcoal addition on the increase of acidolysis ammonia nitrogen was the most significant,and the effect of straw addition on the increase of acidolysis ammonia sugar nitrogen was the most significant.3.Straw addition?mean values of SN0,SN50 and SN100?could significantly reduce the content of acid-hydrolyzed unknown nitrogen and its proportion to total soil nitrogen,while nitrogen application?mean values of CN100,SN100 and BN100?had no significant effect on acid-hydrolyzed unknown nitrogen,while biomass carbon addition?mean values of BN0,BN50and BN100?had significant effect on acid-hydrolyzed unknown nitrogen only in 10-30 cm soil layer;nitrogen application and straw addition only in 10-30 cm soil layer.The content of non-acid-hydrolyzed nitrogen and the proportion of non-acid-hydrolyzed nitrogen increased,while the addition of biomass carbon only increased the content of non-acid-hydrolyzed nitrogen and the proportion of non-acid-hydrolyzed nitrogen in 0-10 cm soil layer.4.Except for the significant interaction between nitrogen and biomass carbon in 5-10 cm soil layer,there was no significant interaction between nitrogen and biomass carbon,nitrogen and straw in 0-30 cm soil layer.5.Under nitrogen application?mean values of CN100,SN100,BN100?and straw addition?mean values of SN0,SN50 and SN100?,the availability of soil acidolysis amino acid nitrogen and acidolysis ammonia nitrogen was higher,while that of soil acidolysis ammonia nitrogen and acidolysis amino sugar nitrogen was higher under biomass carbon addition?mean values of BN0,BN50,BN100?.In summary,carbon and nitrogen addition can generally increase the content of other organic nitrogen components and their proportion in total nitrogen except acidolysis unknown nitrogen,but does not change the relative content of each component and total nitrogen;the availability of soil organic nitrogen components has nothing to do with the content of nitrogen components;the availability of soil acidolysis amino acid nitrogen and acidolysis ammonia nitrogen is higher under nitrogen application and straw addition treatment,while biomass carbon addition is higher.Adding acidolysis ammonia nitrogen and acidolysis aminosaccharide nitrogen is more effective.