Spatial and temporal variation of nitrogen exported by runo from
sandy agricultural soils |
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Authors: | ZHANG Ming-kui WANG Li-ping and HE Zhen-li |
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Institution: | 1. College of Natural Resources and Environmental Sciences,Zhejiang University,Hangzhou 310029,China 2. University of Florida,Institute of Food and Agricultural Sciences,Indian River Research and Education Center, 2199 South Rock Road,Fort Pierce,FL 34945,USA |
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Abstract: | The eutrophication problem has drawn attention to nutrient leaching from agricultural soils.and an understanding of spatial and temporal variability is needed to develop decision-making tools.Thus,eleven sites were selected to monitor,over a two-year period,spatial and temporal variation of runoff discharge and various forms of N in surface runoff in sandy agricultural soils.Factors influencing the variation of runoff discharge and various forms of N in surface runoff were analyzed.Variation of annual rainfall was small among 11 situs.especially between 2001 and 2002.However,variation of annual discharge was significant among the sites.The results suggest that rainfall patterns and land usc had significant effect on discharge.The concentrations of total N,total kjeldahl N (TKN),organic matter-associated N (OM-N),NO3--N,and NH4 -N in the runoff ranged widely from 0.25 to 54.1,0.15 to 20.3,0.00 to 14.6,0.00 to 45.3,and 0.00 to 19.7 mg/L,respectively.Spatial and temporal variations in the N concentration and runoff discharge were noted among the different sites.Annual loads of N in the runoff varied widely among monitoring sites and depend mainly on runoff discharge.High loads of total N,OM-N,NO3--N,and NH4 -N in the runoff either in citrus groves or on vegetable farms occurred from June to October for each year,which coincided with the rainy season in the region.This study found that N in surface runoff was related to rainfall intensity,soil N level,and fertilizer use. |
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Keywords: | citrus grove nitrogen rainfall runoff sandy agricultural soils spatial and temporal variation vegetable farms agricultural soils runoff nitrogen variations temporal fertilizer use N level study related rainfall intensity rainy season region citrus vegetable year High monitoring concentrations different widely |
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