Soil water and alfalfa yields as affected by alternating ridges and furrows in rainfall harvest in a semiarid environment

We studied the effect of alternation of ridge and furrow for harvesting rainfall on alfalfa (Medicago sativa L.) grassland performance in the 3 years of 2001–2003. Five treatments were designed in this study: (1) conventional cultivation in a flat plot without mulch (CK), (2) plastic-mulched ridge with both ridge and furrow 30 cm wide (M30), (3) plastic-mulched ridge with both ridge and furrow 60 cm wide (M60), (4) bare ridge with both ridge and furrow 30 cm wide (B30) and (5) bare ridge with both ridge and furrow 60 cm wide (B60). Treatments of mulching ridge/furrow improved water and temperature conditions in the topsoil (0–20 cm) in mid-April. Mulching ridge/furrow increased growth of the individual alfalfa plants, and decreased the plant density. Mulching ridge/furrow helped alfalfa absorb water from the deep soil. The total forage yield of alfalfa in M30 and M60 treatments in the 3 years was higher than in control (CK) by 10.7 and 40.3%, respectively. On the basis of the 0–500 cm soil layer, the water use efficiency (WUE) was 8.12 and 9.97 kg ha−1 mm−1 in M30 and M60, respectively, whereas it was only 7.20 kg ha−1 mm−1in CK. The total forage yield of alfalfa in B30 and B60 in the 3 years was lower than that in CK by 14.2 and 28.3%, respectively. The WUE was only 6.26 and 5.38 kg ha−1 mm−1 in B30 and B60, respectively, significantly lower than that in CK. It is concluded that mulching the 60 cm wide ridges with 60 cm wide furrows serve as a model for alfalfa establishment on large scale in the semiarid region.