Abstract: In this research two experiments were conducted to investigate the effects of slope and cultivation system on soil erosion control. In Experiment 1, a completely random design was used to study the runoff efficiency and the rainfall threshold to produce runoff for ridges along different slopes (0°, 5° and 10°). In Experiment 2, a split-plot design with slope (5° and 10°) as the main plot factor and tillage method (traditional planting, open ridging and tied-ridging) as the split-plot treatment was adopted to study the effect of tied-ridging rainwater harvesting on soil moisture, runoff, sediment yield, nutrient loss, alfalfa fodder yield and water use efficiency (WUE). The mean runoff efficiencies for ridges along slopes of 0°, 5° and 10° were 88.2%, 91.1% and 92.7%, respectively. The threshold precipitation to produce runoff for the respective treatments was 1.55, 1.33 and 1.00 mm, respectively. Compared with traditional planting, the decreases in runoff, runoff efficiency, sediment yield, total nitrogen loss, total phosphorus loss and organic matter loss for open ridging were 62.3%-67.9%, 51.0%-54.5%, 95.6%-96.4%, 95.3%-96.2%, 95.3%-96.1% and 94.1%-95.6%, respectively, whereas the corresponding decreases for tied-ridging were 76.4%-79.9%, 67.8%-68.2%, 98.4%, 98.1%-98.2%, 98.2% and 97.8%-97.9%, respectively. The open ridging and tied-ridging increased shallow-layer (0-60 cm) soil moisture. The increase in alfalfa forage yield and WUE for open ridging were 40.3%-50.4% and 4.4-11.5 kg·ha^-1·mm^-1, respectively. The corresponding increases for tied-ridging were 16.0%-18.7% and 2.0-5.3 kg·ha^-1·mm^-1. The runoff, runoff efficiency, sediment yield, total nitrogen loss, total phosphorus loss and organic matter loss for the 10° slope were 1.44, 1.40, 2.34, 2.24, 2.39 and 1.97 times greater than those for the 5° slope. Lastly, average soil water storage, alfalfa fodder yield and WUE for the 5° slope were 1.05, 1.28, and 1.41 times greater than those for the 10° slope. Tied-ridging rainwater harvesting was particularly beneficial for reducing runoff, sediment yield and nutrient loss. Open-ridging was offered particular effects on increase of alfalfa fodder yield and WUE.

Key words: tied-ridging rainwater harvesting, runoff, sediment yield, nutrient, production pattern