Responses of soil water, nitrate and yield of apple orchard to integrated soil management in Loess Plateau, China

The managements of fertilization and surface mulching in apple orchards have both potential positive environmental and productive effects due to their benefits of water infiltration and soil nitrate movement in field ecosystem. However, the research to date had tended to focus on single measure rather than both together. The aims of this study were to determine how integrated management for apple orchards influenced spatial and temporal changes of soil water content (SWC) and soil water storage (SWS), illustrate the effects on reducing soil nitrate accumulation (SNA) and promoting N uptake, determine the impacts of water use efficiency (WUE) and apple yield. We applied three treatments for demonstration contrast experiments, traditional farming measure (chemical fertilizer, FM), existing management measure (chemical fertilizer plus manure, plastic film mulch in-row, EM) and optimized management measure (chemical fertilizer plus manure, plastic film mulch in-row and cover crop inter-row, OM). We found that the SWC in 3 m soil layers was influenced by the tree growth period, the clearly benefits of OM to invariably increase SWS in 3 m soil layer were observed in different period, especially in dry year. During the tree growth, the OM treatment significantly increased rainwater retention in deep soil (below 1 m) and received a maximum value of SWS in 3 m soil layers. Apple yield was significantly enhanced in OM, but the water consumption in each treatment had no obvious difference, and consequently WUE was elevated compared with EM and FM. The SNA after the apple harvest was significantly decreased under the OM, especially in 2−3 m soil depth. Meanwhile, total N in fruits and leaves in OM were significant higher than FM, indicating that the risk of N leaching was reduced, and the N was effectively used by trees. Regression relationships between SNA and SWS were significantly negative in the dry year, means that the OM would perform better in mitigating soil desiccation and soil nitrate leaching in dry climatic condition. This study highlights integrated soil management is a considerable practice for apple orchards in Loess Plateau and the rain-fed area around the world.