The effects of cocksfoot cover crop on soil water balance, evapotranspiration partitioning, and system production in an apple orchard on the Loess Plateau of China

Abstract

Cover cropping in orchards has been advocated on the Loess Plateau of China to prevent soil erosion and provide additional forage production; however, the effects of cover crops on water use processes in orchards have not been fully investigated and soil water sustainability in the system is still unclear. This study was conducted to investigate the effects of intercropping cocksfoot (Dactylis glomerataL.) and cocksfoot cutting management on soil water balance, evapotranspiration (ET) and its partitioning, and production in an apple orchard (Malus pumila M.). Field experiments were conducted at Qingyang experiment station in 2016-2018. The apple trees were at a spacing of 4 m × 4 m, and three soil management patterns were applied: clean tillage (CT), 2.4 m-wide cocksfoot strips set up between tree rows that were harvested with a high frequency (HF), and cocksfoot strips harvested with a low frequency (LF). The results showed that decline in soil water content in the dry season was promoted in the cover crop treatments. In tree interrow positions the soil water depletion was increased only in the 0–100 cm soil layer while in tree row positions the depletion in both the 0–100 and 100–200 cm soil layers was significantly increased (P < 0.05). Soil water replenishment in the 200–300 cm soil layer in the rainy season was reduced in the cover crop treatments. Increasing the harvesting frequency of cocksfoot could reduce its negative effects on soil water content in dry periods. The total system ET in LF was 477.7, 441.0 and 540.5 mm in 2016, 2017 and 2018, respectively, which was significantly greater than that in HF and CT in the dry year of 2016 and was comparable with two other treatments in 2017 and 2018. ET under the tree canopy was increased after sowing cocksfoot, but large amounts of water were saved by converting soil evaporation to cocksfoot transpiration. Sowing cocksfoot did not exert a significant negative effect on apple production in any of the three years (P > 0.05), and 2.07–6.32 t ha-1 additional forage biomass was produced. Cocksfoot with greater harvesting frequency is suggested to be applied to conserve soil and water in apple orchards in our study area.