Optimum ridge width and suitable mulching material for sainfoin production with ridge–furrow rainwater harvesting in semiarid regions of China

Abstract

Ridge-furrow rainwater harvesting (RFRH) with mulch offers farmers means to address drought, water loss, and soil erosion in arid and semiarid regions. Plastic film is widely used as a mulching material for RFRH; however, contamination of arable lands by its residual is a serious concern. We compared various mulches, including a biodegradable film for RFRH planted with sainfoin (Onobrychis viciifolia). A field study was conducted to (1) estimate runoff efficiency from three ridge widths using three different mulching materials; and (2) assess the effects of ridge widths and mulching materials on topsoil temperature, soil water storage, fodder yield, fodder nutrition, and water use efficiency (WUE) of RFRH planted with sainfoin, during 2015 and 2016. The predicted runoff efficiency for MCS30, MCS45, MCS60, BF30, BF45, BF60, PF30, PF45, and PF60 [MCS, BF, and PF are abbreviations for ridges with manually compacted soil, mulched with biodegradable film and with plastic film, respectively, subscripts 30, 45, and 60 refer to ridge widths (cm) all with 60 cm furrow width] was 9.9%, 22.2%, 24.7%, 85.3%, 88.8%, 92.7%, 85.9%, 89.7%, and 93.3%, respectively. The practice of RFRH, especially BF and PF, resulted in increased topsoil temperature at ridge tops and increased soil water content at furrow bottoms but decreased topsoil temperature at furrow bottoms. MCS decreased actual fodder yield, but BF and PF increased actual fodder yield. Compared to flat planting (FP), the decrease of actual fodder yield for MCS30, MCS45, and MCS60 was 7%, 15%, and 18%, respectively, for 2015 and 2016, but the increase of actual fodder yield for BF30, BF45, BF60, PF30, PF45, and PF60 was 10%, 8%, 6%, 15%, 13%, and 8%, respectively. Mean WUE for MCS, BF, and PF was 1.58, 1.64, and 1.70 times greater than that for FP, respectively. High soil water content and high soil temperature in RFRH, especially for BF and PF, resulted in increased crude protein and phosphorus content of the fodder produced but resulted in decreased acid detergent fiber and neutral detergent fiber content of fodder. Mean crude protein content for BF and PF was 1.25 and 1.30 times greater than that for FP, respectively, whereas phosphorus content for BF and PF was 1.37 and 1.32 times greater than that for FP. The optimum ridge width for BF was 35–36 cm, whereas for PF, it was 36–42 cm. The RFRH design should conserve water and improve fodder yields and quality.