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Effect of Agricultural Practice on Reactive Nitrogen Pool in Soil and Environment

Author: TangYanLing
Tutor: ZhaoMingXian
School: Jilin Agricultural University
Course: Environmental Engineering
Keywords: Human agricultural activities Reactive nitrogen Nitrate Environmental Effects
CLC: S153
Type: Master's thesis
Year: 2005
Downloads: 272
Quote: 3
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Abstract

Human activities, especially agricultural production activities has greatly promoted the global nitrogen fixation and the nitrogen cycle, but also caused serious environmental problems. Reactive nitrogen as a natural biological direct use of nitrogen forms, to meet the food production required for the survival of mankind has universal significance, and therefore has been widely used in agricultural production, After this many environmental problems, however, also increasingly cause more people concerned about their environmental behavior. Input of reactive nitrogen in the soil in the agro-ecological system, mainly refers to nitrogen fertilizer, nitrogen fertilizer into the soil there are three basic whereabouts uptake by plants, residues in the soil, loss through a variety of channels. Which residual reactive nitrogen to nitrate-based, and the most serious environmental impact of this form of reactive nitrogen. Out to improve crop yield considerations with the development of agricultural production, excessive application of nitrogen fertilizer is widespread, which lead to a lot of residual nitrate in the soil profile after harvest. Part of these residual nitrate may be next season crop use, leaching to deep-rooted and shallow groundwater, part of denitrification occurs to N _{the the 2} O or N _{2 form of escape soil. Nitrate leaching is the main reason causing nitrate pollution of groundwater, the denitrification release N _{of 2} O is also one of the greenhouse gases that cause global warming. Intensive agro-ecosystems, forests and grasslands, and other natural ecosystems to maintain the natural state of production in the absence of direct disturbance by human activities. Previous studies rarely based on Cycle Conversion of nitrogen in the soil of natural ecosystems to explore the impact of human agricultural activity of reactive nitrogen in the soil of agricultural ecosystems library, to reveal its environmental effects. Therefore, we selected Northeast China natural ecosystems (forests and grasslands) soil as a reference, the human agricultural activities typical agro-ecosystems (farmland, greenhouses and long-term positioning experimental field) reactive nitrogen storage capacity of the soil profile and its several important component ^{(NH ₄ -N and NO ₃ ^{- -N mineralized N, microbial nitrogen and fixed ammonium) the degree of deviation from the natural causes and impact on the environment; typical ecosystems (forests, grasslands, farmland, greenhouses and long-term positioning experimental field) in the soil library of reactive nitrogen mineralization and nitrification potential research, evaluation different the nitrate supply capacity of the ecosystem, nitrogen conversion mechanism of human activity and environmental effects. The main findings are as follows: the intervention of human cultivation, fertilization, irrigation, and other agricultural management practices, its profiles of various types of soil for agricultural ecosystems NO _a ^{- -N the cumulative amount has reached a very high level. Greenhouse soil profile 0 ~ 200cm in NO ₃ ^{- -N accumulated the highest average of 717kg hm ^{-2 , the equivalent of ordinary farmland three times the annual application rate of soil nitrogen fertilizer. The NO in farmland black soil, chernozem and white bentonite ₃ ^{- -N cumulative amount reached 78.3kg hm ^{-2 , 124.6 kghm ^{-2 and 20.6 kg hm ^{-2 . This is relative to the natural state of the forest and grassland were 3.2kg hm ^{-2 and 13kg hm ^{-2 of the cumulative amount of already serious deviation from the natural state . For the NO ₃ ^{- -N further migration to the environment outside of the soil, leaving a hidden danger. Topsoil NO ₃ ^{- -N generation by mineralization and nitrification these two characteristics of the impact of a continuous process of role. Forest topsoil highest mineralization rate reached 10.7kg hm ^{-2 d ^{-1 , however, due to its nitrification rates mineralization rate only}}}}}}}}}}}}}}}}

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