[Soil nitrogen and organic matter losses under water erosion]

The results of artificial water-scoured experiment show that with the increase of water-scoured intensity, the losses of nitrate and ammonium in runoff, and those of organic matter and total N in sediment increased greatly, while the enrichment ratios of organic matter and total N in sediment reduced correspondingly. When the soils in gully-hilly loess region were fertilized with same amount of NH4NO3, the ammonium and nitrate loss in runoff was respectively 0.9-3.5% and 8.2-19.7% of the application amount. Nitrate mainly lossed in runoff, not in sediment. The correlation coefficient of soil erosion module, organic matter and total N loss with > 20 microns soil aggregates was -0.8935, -0.7928 and -0.8151, respectively. The content of > 20 microns soil aggregates could be used as an index to differentiate the soil organic matter and total N loss.