Polyacrylamide and Rill Flow Rate Effects on Erosion and Ammonium Nitrogen Losses

Abstract

Overland flow caused by rainfall is one of the critical factors influencing soil erosion and loss of soil nutrients. Therefore, the study on the mechanism and controlling measures of soil nutrient transport proposed is considered important. A simulation experiment was performed to investigate the effects of polyacrylamide application rates (0, 1, 2, 4, and 8 g/m²) and flow rates (400 ml/min, 600 ml/min, and 800 ml/min) on runoff, infiltration rate, soil losses, and the concentration of ammonium nitrogen (NH₄⁺) in runoff at loess slope (0.8 m (width) × 1.5 m (length) and 5°). As the results suggest runoff, sediment loss, and soil nutrient loss increased by increasing flow rate. Applicable amount of polyacrylamide (PAM) can effectively increase infiltration and reduce soil erosion, but excess amount of dissolved PAM would plug porosity of soil which could decrease the infiltration. The ammonia nitrogen loss amount was decreased with the increase of the PAM application rate. The ammonia nitrogen loss amount respectively decreased by 40.0%, 57.0%, 59.1%, and 63.4% with the PAM application rate of 1, 2, 4, and 8 g/m². The best performance with the coefficient of determination (R²) showed that the ammonium transport with runoff can be well described by the proposed model in flow scour experiments of this study. Furthermore, the model parameter b has a significant positive exponential relation with the total amount of sediment.

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