Terrestrial environment

Spatial and temporal variation of nitrogen exported by runo fromsandy agricultural soils

ZHANG Ming-kui , WANG Li-ping , HE Zhen-li


Received November 03, 2006,Revised April 26, 2007, Accepted , Available online

Volume 19,2007,Pages 1086-1092

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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 runo discharge and various forms of N in surface runo in sandy agricultural soils. Factors influencing the variation of runo discharge and various forms of N in surface runo were analyzed. Variation of annual rainfall was small among 11 sites, especially between 2001 and 2002. However, variation of annual discharge was significant among the sites. The results suggest that rainfall patterns and land use had significant e ect on discharge. The concentrations of total N, total kjeldahl N (TKN), organic matter-associated N (OM-N), NO3--N, and NH4+-N in the runo 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 runo discharge were noted among the di erent sites. Annual loads of N in the runo varied widely among monitoring sites and depend mainly on runo discharge. High loads of total N, OM-N, NO3--N, and NH4+-N in the runo 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 runo was related to rainfall intensity, soil N level, and fertilizer use.

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