Effects of Contour Hedgerow Intercropping on Nutrient Losses from the Sloping Farmland in the Three Gorges Area, China

Eutrophication is recognized as one of the major environmental problems in the Three Gorges Reservoir. Contour hedgerows have been used as a major soil and water conservation measure in this area. Accordingly, a two-year study was conducted to investigate the effects of contour hedgerow intercropping on nutrient loss from sloping farmland in this area. Four treatments were applied: (1) Maize + Soybean, (2) Maize, (3) Maize + Alfalfa, and (4) Maize + Hemerocallis citrina Baroni. Results indicated that nutrient loss in the control treatment (Maize) was serious, especially the average loss flux of total nitrogen (2245.8 mg) and total phosphate (2434.2 mg) in a typical rainfall event. However, the nutrient losses by runoff in the other three treatments with contour hedgerow intercropping showed significant reduction. Compared with the control treatment, the total nitrogen loss in the Alfalfa and Hemerocallis citrina Baroni decreased by 80.9% and 85.0%, respectively, and the total phosphorus loss in the two treatments decreased by 91.2% and 92.5%, respectively. Therefore, it is concluded that nutrient losses could be reduced by using contour hedgerows in the Three Gorges Region. Reducing runoff volume and sediment loss was the main mechanisms of contour hedgerow intercropping to reduce nutrient loss.