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Characterization of dissolved nitrogen and phosphorus transportation in farmland runoff under heavy rain—take Laoshan Reservoir watershed as example |
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Abstract Runoff plots of five representative crops as corn, soybean, peanut, sweet potato, cucumber were established in watershed of Laoshan Reservoir. Dissolved nitrogen and phosphorus concentrations in the runoff were observed under heavy rain or rainstorm in 2009~2010, and the basic characteristics of rainfall and the information of various types of crops were recorded. The results showed that the event mean concentrations (EMC) of ammonia nitrogen (NH4+-H), nitrate nitrogen (NO3--N) and dissolved phosphorus (DP) were significantly different across the five runoff plots. Crop types and fertilization conditions explained most of the difference. The dissolved nitrogen and phosphorus concentrations in the runoff plots of corn and cucumber were significantly higher than that of other crops, due to the higher amount of fertilization and the smaller leaf area index (LAI) of these two crops. There existed significant negative correlation between dissolved nitrogen and phosphorus losses and crops LAI (P<0.05). The results of correlation analysis between rainfall characteristics and nitrogen and phosphorus transport in the runoff plots showed that the transport load was positively correlated with rainfall and maximum rainfall intensity (P<0.01).
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