Soil quality responses to alfalfa watered with a field micro-catchment technique in the Loess Plateau of China

Abstract

This paper explores the soil responses to alfalfa that is established using a field micro-catchment technique to harvest water under semiarid conditions. The field micro-catchment technique involved setting up ridges and furrows alternately on the flat land. The ridges served as the rainfall harvesting zone and the furrows as the planting zone. Five treatments were set up in this study: (1) conventional cultivation in a flat plot without mulch (CK), (2) plastic mulched ridge with 30 cm width of ridge and furrow (M30), (3) plastic mulched ridge with 60 cm width of ridge and furrow (M60), (4) bare ridge with 30 cm width of ridge and furrow (B30), (5) bare ridge with 60 cm width of ridge and furrow (B60). The mulching treatments increased the productivity of seeded alfalfa and significantly ( p < 0.05) increased water use efficiency, causing the soil organic carbon (SOC), total soil nitrogen (TSN) and C/N ratio to increase. We also found that the alfalfa root system was very good at breaking up the plowing pan created by many years of tillage. In the M30 and M60 treatments, the total forage yield during the 3 years was higher than in CK by 10.7% and 40.3% respectively, whereas the total forage yield over the 3 years in the B30 and B60 treatments were lower than in the CK treatment by 14.2% and 28.3%, respectively. The water use efficiency in the mulching treatment was significantly higher than in the other treatments. After 3 years (2001–2003), the SOC content in ridge and furrow treatments (M30, M60, B30 and B60) was increased by 7.4%, 14.2%, 4.5% and 1.8%, respectively, contrasting with a decrease of 3.5% in the CK treatment. The increase in SOC positively correlated ( R 2 = 0.6257) with the forage yield of alfalfa in the ridge and furrow treatments. The TSN for CK, M30, M60, B30 and B60 increased by 0.35%, 1.70%, 2.30%, 0.75% and 0.64%, respectively by the end of the 3 years. However, we found that the available phosphorus (P) in the mulch treatments during the 3-year period decreased rapidly indicating that it is necessary to apply P fertilizer to alfalfa-cultivated land under these management conditions. In conclusion, the ridge and furrow with mulch treatments, especially M60 treatments, proved to be a better pattern for alfalfa establishment, soil quality and nutrient cycling under semiarid conditions.