Sediment control and fodder yield increase in alfalfa (Medicago sativa L) production with tied-ridge-furrow rainwater harvesting on sloping land

Drought, water loss and soil erosion are the main factors restricting grain production and economic development in the semiarid hill areas of Loess Plateau, China. A field experiment was conducted to determine the effects of different tillage systems (open-ridging and tied-ridging) on soil water moisture, runoff, sediment yield, fodder yield and water use efficiency (WUE) on 2 slopes (5° and 10°), using traditional planting (without ridges and furrows) as a control, during 2 consecutive alfalfa growing years: 2015 and 2016. Results indicated that the benefits of fodder yield and WUE increase from tillage system were more effective than the benefits from slope gradient on slight sloping land. Open-ridging and tied-ridging decreased runoff and sediment transport and increased soil moisture, fodder yield and WUE of alfalfa. The decrease of sediment for open-ridging and tied-ridging was 85.1% and 88.4%, respectively, for slopes of 5°, while it was 83.9% and 89.0% for slopes of 10°. Only 7–10% rainfall events produced runoff and 4–6% rainfall events produced sediment. The mean runoff efficiency for traditional planting, open-ridging and tied-ridging was 11.6%, 9.1% and 6.7%, respectively, for slopes of 5°, while it was 13.4%, 10.0% and 7.8% for slopes of 10°, over 2 years. Increase of fodder yields for open-ridging and tied-ridging was 34.6% and 19.8%, respectively, for slopes of 5°, while it was 32.7% and 20.6% for slopes of 10°, over 2 years. The average WUE for open-ridging and tied-ridging was respectively 1.96 and 1.85 times greater than that for traditional planting, for slopes of 5°, while it was 1.88 and 1.77 times greater than that for traditional planting, for slopes of 10°, over 2 years. The mean runoff and sediment for slopes of 10° was 1.14–1.16 and 1.19–1.57 times that for slopes of 5°, respectively. The differences of fodder yield and WUE between slopes of 5° and slopes of 10° were not significant. Tied-ridging rainwater harvesting offered particular effects on water and soil conservation, while open-ridging offered particular effects on fodder yields and WUE enhancement during the first and the second growing seasons.