Study On The Soil Nitrogen Transformation Processes And Influencing Factors In Arid Area

Arid area and its ecological system is vulnerable, lack of soil mineral elements,nitrogen content is low, nitrogen is considered to be second only to moisture influencefactors of plant growth, and due to the influence and control of various environmentaland climatic conditions, the distribution and transformation process of nitrogen ismore special. Therefore, the research of soil nitrogen transformation process and theenvironmental effects in arid area, is essentially significant to reveal the distributionfeatures of the arid soil nitrogen, land desertification, vegetation distribution,biodiversity decrease, ecological system evolution tendency and the nature of nitrogencycle. The arid soil nitrogen conversion rate and its environmental impact factor weremeasured to analyze arid soil nitrogen distribution, the characteristics of the nitrogenconversion, different nitrogen of the interaction between the transformation process,and explored the main environmental factors of influence and control inarid soil nitrogen transformation process.The main results are as follows:(1) Nitrogen distribution has certain regularity in different soil types of soil.There was no statistical difference between nitrate, nitrite and availablenitrogen in different soil types on the distribution. The overall performance is calciumsoil > desert soil, ammonium nitrogen in different soil types on expression isextremely significant difference, they embodied mainly in: sierozem > brown desertsoil > grey desert soil > bog soil > meadow soil. Nitrate and available nitrogencontent in different soil types with the deepening of the soil depth decreased, andnitrite and ammonium nitrogen between layers of the distribution is not obvious.(2) There was no significant difference in the soil nitrogen content amongdifferent types of vegetation. On the whole, tree forest had the highest amount ofnitrate and available nitrogen, the content of cotton field is second, bare land has thelowest content. Soil nitrate vertical distribution in different vegetation types is not identical also, soil available nitrogen content with soil depth decreased; Nitratenitrogen in the horizontal and vertical distribution of different vegetation types of soil,the different is not great; the distribution law of soil ammonium nitrogen inthe various vegetation types is not obvious.（3）With increasing years of continuous cropping, cotton fields showed certainchanges in trends and patterns. While increased and then followed by a decrease withincreasing amounts of soil nitrate and nitrite and available nitrogen with increase ofthe number of years. Ammonium soil nitrogen distribution rule is not so obvious, andoverall performance is first increased and then decreased again of the "N"-shapetrend.(4) The correlation analysis of different forms of nitrogen in the study of nitrogenin arid soil showed that, in addition to the negative correlation between nitrate andammonium nitrogen was not significant, the rest of nitrogen showed a significant andhighly significant relationship, which showed that the mutual influence amongdifferent forms of nitrogen is obvious.(5) As a whole, there is a large differences in the net nitrification rate in thedifferent soil types, the rate of soil from the big net nitrification to small is bog soil >meadow soil >brown desert soil > grey desert soil > sierozem. The vertical directionof net nitration rate was decreased with soil depth of the size of the deepening.Leguminous herb had the highest amount of net nitration rate, the content of treeforest is second, bare land has the lowest content. There was no significant differencein the net nitration rate among different types of vegetation. The vertical distributionhas certain law, in addition to the cotton fields for the A> C>B，the overallperformance is the A> B> C. There was no significant difference in the net nitrationrate with different increasing years of continuous cropping, but its value wasincreased with the increasing years of continuous cropping.(6) Gross nitrification rate was significantly greater than the net nitration rate in arid soil, the highest rate was 22 times of net nitrification. Grey desert soil outside, therest of the soil type net nitrification and gross nitrification distribution had the samerule. There was no significant difference in the denitrification among different typesof soil. The rate of soil from the big denitrification to small is bog soil > sierozem>meadow soil >brown desert soil > grey desert soil. There was a significantdifference in the gross nitrification between trees, shrubs, cotton field and herb, bareland. There were some differences of denitrification in the different vegetation types.With increasing years of continuous cropping, soil gross nitrification rate was the“N”-shaped distribution and denitrification generally was“M”-shaped distribution.(7) Soil mineralization distribution trend and soil net nitrification distributiontrend is roughly same, and soil net mineralization rate of cotton field was lower thanthe similar soil natural sample. The rate of soil from the big ammonification to smallis bog soil>meadow soil > grey desert soil >sierozem >brown desert soil. Netammonification of sierozem was almost zero, and brown desert soil waseven negative.(8) The correlation analysis of different transformation of nitrogen in the study ofnitrogen in arid soil showed that: Among them, the gross nitrification rates and netnitrification, mineralization rate expressed as a highly signification positivecorrelation (P <0.01), and the gross nitrification rates had a signification positivecorrelation with ammoniation (P < 0.05). There was a highly signification positivecorrelation between net nitrification and mineralization rate (P <0.01). The correlationbetween the remaining variables was not significant.(9) In the study of soil physical and chemical properties, soil organic matter, totalnitrogen, total phosphorus of nutrition index the most influenced soil nitrogentransformation process, soil bulk density and porosity were the second, and the soilpH of soil nitrogen conversion rate had no notable effect. In different forms of soilnitrogen, soil available nitrogen and nitrite nitrogen showed a significant or very significant level of positive correlation with soil nitrogen transformation process, soilnitrite nitrogen showed a very significant level of positive correlation with soil netnitrification rate and denitrification rate. Soil ammonium nitrogen andsoil net nitrification rates were highly significant negative correlation. Path analysisresults showed that the order of the soil environment factors which directly influencedthe soil nitrification is the organic matter> porosity> bulk density> nitrate>pH>moisture> P> Conductivity>ammonium nitrogen> nitrite nitrogen>availablenitrogen.