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Experiment Study on Nitrate Transport Characteristics and NO3--N Distribution in Groundwater under Intermittent Infiltration of Surge Irrigation

Author: YinJuan
Tutor: FeiLiangJun
School: Xi'an University of Technology
Course: Hydrology and Water Resources
Keywords: surge irrigation intermittent infiltration technique factors NO3--N transport fertilization applying manner water and fertilization coupling groundwater
CLC: S274
Type: PhD thesis
Year: 2008
Downloads: 200
Quote: 1
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Abstract


On the basis of literature review on surge irrigation,nitrogen fertilizer transport and transformation in soils worldwides,considering irrigation and fertilization practice in China, this research involves laboratory studies and theoretical analyses.This dissertation covers researches on soil water and nitrogen transport characteristics,water and fertilizer coupling characteristics,the concentration of NO3--N in the ground water under surge infiltration with fertilization.Such research should provide the theoretical backgrounds for NO3--N pollution control of groundwater and improvement of nitrogen use efficiency.The main findings are as follows:(1)The capillary water ascending characteristics under in the uniform soil with different groundwater table are researched.The ascending rate of capillary water augments with the initial soil moisture;the height of the capillary water rise increases with time,the capillary water rise velocity decreases with time increasing;the more the initial soil moisture is,the less the time that capillary water reach to the same height is;the relationship between the height of the capillary and the time needed can be simulated by power functions.The little the initial soil moisture is,the more the underwater supply volume when soil water reach balance is and the longer the balance time is;there are power function relationship between the capillary water supply and time,and linear power function relationship between the capillary water rise velocity and the height of the capillary water rise.(2)The infiltration capacity,wetting front transport,soil water content distribution, NO3--N transport characteristics and the NO3--N concentration distribution of round water under intermittent and continuous infiltration with fertilizer solution are researched.Comparing with continuous infiltration,intermittent infiltration can decrease infiltration capacity and the reduction effects were more significant in the second cycle.Wetting front of the under intermittent infiltration with fertilizer solution moves slower than under continuous infiltration and the speed decreases with cycle number.Model for calculating transport distance of the wetting front under intermittent infiltration based on continuous infiltration data is proposed.The soil water content is more evenly distributed under intermittent infiltration than continuous infiltration.Soil NO3--N front under intermittent infiltration moves slowly than under continuous infiltration,which favors NO3--N conservation in shallow soil layer.The relationship curve between concentration NO3--N and soil water content is a "L" shape under intermittent and continuous infiltration effected by underwater.Comparing with continuous infiltration,the relationship curve is steeper under intermittent infiltration,and the NO3--N increment in the ground water is more under continuous infiltration.(3)The influences of technique factors on the infiltration capacity,wetting front transport, soil water content distribution,NO3--N transport characteristics and the NO3--N concentration under intermittent infiltration are researched.The infiltration quantity and wetting front transport models containing different affecting factors under intermittent infiltration with solution are established.In this experiment,the optimal cycle rate is 1/3,which leads to NO3--N being more easily stored in shallow soil layer and weakens the trend of NO3--N leaching and lightens groundwater NO3--N pollution;The infiltration rate,the concentration front transport distance of NO3--N and the increment of concentration of NO3--N in groundwater are least when the cycle number is 3.The wetting front and the concentration front transport distance and the NO3--N concentration increment in the groundwater increase with the irrigation water quota increasing.There is power function relationship between the increment of NO3--N concentration in the groundwater and the groundwater depth.(4)Coupled movement characteristics of soil water and nitrogen under intermittent infiltration with different fertilization concentration are researched.The infiltration capacity,the transport distance of NO3--N concentration front and the value of NO3--N front increases with the fertilizer solution concentration.After intermittent infiltration with fertilizer solution,the relationship curve between concentration NO3--N and soil water content is a "V" shape,in 0~72cm soil layer,NO3--N concentration and the soil water content are large.The NO3--N concentration decreases with soil water content decreasing.The more fertilization solution concentration is,the little the influence of soil water content on NO3--N concentration.The NO3--N concentration is close to initial value in 72cm~150cm,the "V" curve becomes more slipperier and the distribution of NO3--N concentration and soil water content are uniform. The NO3--N concentration decreases with soil water content increasing.In 0~76cm, NO3--N concentration increases more than after infiltration,the more solution concentration is,the more soil water content effect NO3--N concentration;NO3--N in underwater from irrigation water mainly distribute in the shallow groundwater,the more solution concentration is,the more NO3--N enters groundwater and the more seriously NO3--N pollutes,NO3--N entering groundwater is most after irrigation with different fertilization concentration and decreases gradually with redistribution time.The exponent function exists between the NO3--N increment of different concentration solution and groundwater depth.(5)The effect of fertilization applying manner on soil water content,nitrogen transport characteristic and NO3--N concentration in the groundwater are researched.The infiltration capacity of surface applying fertilization is more than chemigation and deep applying fertilization; in the same infiltration time,the order of wetting depth is surface applying fertilization>deep applying fertilization>chemigation>no applying fertilization;the infiltration volume under intermittent infiltration with different fertilization applying manner is developed;in the same wetting depth,the order of soil water content is surface applying fertilization>chemigation>deep applying fertilization after redistribution for 1 day;the fertilization applying manner has great influence on NO3--N transport and distribution under intermittent infiltration.NO3--N in the wetting scope under chemigation infiltration distributes uniformly,while the NO3--N under surface applying fertilization and deep applying fertilization mainly distributes in the some depth and transports gradually to deeper soil with time;the NO3--N transports most fast with water under surface applying fertilization,comparing with surface applying fertilization and deep applying fertilization,intermittent infiltration with fertilizer solution favors the NO3--N conservation in shallow soil,and decreases effectively soil water and deep seepage of NO3--N; NO3--N concentration in the groundwater under intermittent infiltration with different fertilization applying manner increases with the underwater depth and infiltration time;the increase ration(the present of NO3--N concentration increase absolute value under different infiltration time to NO3--N increase gross under total infiltration time)of NO3--N concentration groundwater decreases with infiltration time,the increase ratio of NO3--N concentration is most after infiltration and least after redistribution for 5 days,the exponent function exists between the NO3--N concentration increment and groundwater depth under different fertilization applying manner,chemigation favors the improvement of the nitrogen use efficiency and mitigate the nitrogen pollution in groundwater.

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CLC: > Agricultural Sciences > Agricultural Engineering > Irrigation and water conservancy > Irrigation system and management
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