The effects of contour hedges and reduced tillage with ridge furrow cultivation on nitrogen and phosphorus losses from sloping arable land

Agricultural nonpoint sources of nitrogen and phosphorus pollution are thought to pose great threats to the regional water quality in the Three Gorges area (TGA) of China. To explore the effects of protective methods on soil and nutrient losses from sloping arable land, rainfall runoff plot experiment was conducted from May 2010 to May 2011. For a rotation of wheat and maize, four treatments with three replicates were set up: H1, planting Vetiveria zizanioides contour hedgerows; H2, planting alfalfa contour hedgerows; H3, wheat intercropped with horsebean and maize intercropped with soybean, reduced tillage, and ridge furrow cultivation; and H4, conventional management. Nitrogen and phosphorus losses via surface and subsurface runoff were analyzed. When compared with that in H4, sediment phosphorus losses from plots of H1, H2, and H3 were significantly reduced by 46.61, 30.51, and 37.29%, respectively, while surface runoff total phosphorus loss was reduced by 45.38, 28.46, and 34.62%, respectively. Sediment nitrogen and surface runoff total nitrogen losses were not reduced significantly. Sediments were highly enriched with organic matter and nutrients, and decaying organic matter from plant residuals contributed to sediment nitrogen and phosphorus losses. In sandy loam sloping arable land, contour hedgerows and ridge furrow cultivation were effective in reducing phosphorus loss via surface runoff. However, subsurface runoff is the primary path for nutrient losses, especially for nitrogen loss. Accordingly, attention should be given to improve the management of fertilizer nutrients, soil water, and plant residuals in sandy loam slope land.