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Nitrogen and P in surface runoff and eroded sediment from cropland areas can contaminate streams and lakes. Runoff losses of N and P were determined in a small field plot (14.3×24.8 m) of peach orchard from March to November in 1999. Nitrogen and P were applied in the rate of 172 and 46 ㎏/㏊ using chemical fertilizer and mixed oil cake fertilizer. During the season, in 26 rainfall events, 421.5 ㎥/㏊ of runoff including 1,989 ㎏/㏊ of soil loss was collected. Concentrations of total-N, NO₃-N, NH₄-N, total-P and PO₄-P in runoff samples were in the range of 4.7∼171.0, 0.1∼188.0, 0.13∼3.36, 0.58∼4.99 and 0.05∼3.71 ㎎/ℓ, respectively. Total loss of N was 16.39 ㎏/㏊ and 75% of the loss was NO₃-N. Total loss of P was 1.04 ㎏/㏊, and PO₄-P and sediment bound P accounted for 47 and 27% of the total loss, respectively. The losses of N and P were about 9.5 and 2.3% of the applied N and P in the plot, respectively. Although the loss of N or P would be relatively small in agricultural aspect, considering the high concentrations of N and P in runoff, loss of N and P from croplands should be controlled to reduce the eutrophication problem of stream waters.
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