EFFECT OF RIDGE AND FURROW MICRO-CATCHMENT ON SOIL WATER IN SEEDED MEDICAGO SATIVA GRASSLAND IN THE SEMIARID LOESS HILL AND GULLY REGION OF NORTHWESTERN CHINA

Abstract

Aims The semiarid loess hill and gully region of northwestern China is a pasture and agriculture transitional zone lacking water resources for irrigation. The agroecosystem in this region is very vulnerable. An effective method to improve the ecosystem is to combine agriculture with animal husbandry, in which productive grassland plays a key role. However, water is the main limitation on grassland production in this region. We studied the effect of alternating ridges and furrows (for harvesting rainfall) on alfalfa (Medicago sativa) forage yield and soil water. Methods Five treatments were compared: 1) conventional cultivation in a flat plot without mulch (CK), 2) plastic mulched ridges with 30 cm wide ridges and furrows (M30), 3) plastic mulched ridges with 60 cm wide ridges and furrows (M60), 4) bare ridges with 30 cm wide ridges and furrows (B30), and 5) bare ridges with 60 cm wide ridges and furrows (B60). We measured soil water consumption, forage yield of alfalfa and soil water profile in all treatments. Important findings The water use efficiency of M30 and M60 treatments was greater than that of CK by 13% and 41%, respectively. The total forage yield of alfalfa of M30 in four years was not significantly different from that of CK, but the total forage yield of M60 was significantly higher than that of CK by 41%. In both bare treatments, the total forage yield of alfalfa was lower than in CK. In the 3rd alfalfa growing season, the 150 cm soil layer was the balance point of water supplement and soil water consumption. Below 150 cm, soil water can not be supplied by rainfall. Water at 200-500 cm soil depth was close to the permanent wilting point after four years. This study indicates that the M60 treatment is the optimum model for alfalfa establishment in this region. However, after the alfalfa phase, the shallow-root crop must be planted to restore soil water content for subsequent conventional crops.