Effects of rainwater harvesting system on soil moisture in rain-fed orchards on the Chinese Loess Plateau

Abstract

Rainwater is a primary water source for the hilly and gully region of the Loess Plateau where an improved efficiency of rainwater utilization is crucial for sustainable agricultural development. A new system, comprised of rainwater harvesting, concentrating infiltration with multi-holed pipe and mulching (RIM), was designed to sustain soil moisture at a proper level in rain-fed orchards in the hilly and gully loess region of China. This study monitored changes in soil moisture and distribution over soil profiles using four treatments: (a) RIM1 with two rainwater harvesting areas, two infiltration pipes and film mulching, (b) RIM2 with one rainwater harvesting area, one infiltration pipe and film mulching, (c) film mulching (FM) only and (d) traditional apple orchard as a control treatment (CK) as a baseline in this experiment. The results showed that mean soil moisture content (SMC) in a range of soil layer between 0 cm and 300 cm for RIM1 and RIM2 treatments increased by 43.01% and 34.78% in 2018 and 30.55% and 26.41% in 2019, respectively. Dividing the soil vertical profile into three layers, i.e., an easy-changing layer (0−60 cm), an increasing or decreasing layer (60−180 cm), and a relatively steady layer (180−300 cm), this study examined the vertical changes of soil moisture. The RIM1 and RIM2 treatments induced a large increase in the size and depth of wetted areas over the whole soil layers. The soil moisture was replenished to a horizontal distance of 1.5 m and 2.5 m apart from the trunk within the soil layer between 60 cm and 300 cm under the RIM1 treatment while only the horizontal distance of 1.5 m apart from the trunk under the RIM2 treatment. While the seasonal variation of SMC in the easy-changing soil layer (0−60 cm) corresponded to precipitation consistently, the SMC in the deep soil layers (60−300 cm) was not sensitive to precipitation. As a result, the treatments of RIM1, RIM2 and FM improved apple yield and crop water productivity compared with those under the control treatment. In particular, the RIM1 treatment performed the best among the treatments investigated in this study. The results highlighted the efficiency of the RIM system in enhancing the soil moisture, which may be useful to improve an orchard production for rain-fed orchards in the loess hilly and gully region of China.