Abstract
Crop coefficients are critical to developing irrigation scheduling and improving agricultural water management in farmland ecosystems. Interest in dwarf cultivation with high density (DCHD) for apple production increases in Aksu oasis, southern Xinjiang. The lack of micro-irrigation scheduling limits apple yield and water productivity of the DCHD-cultivated orchard. A two-year experiment with the DCHD-cultivated apple (Malus × domestica ‘Royal Gala’) orchard was conducted to determine crop coefficients and evapotranspiration (ETa) with the SIMDualKc model, and to investigate apple yield and water productivity (WP) in response to different irrigation scheduling. The five levels of irrigation rate were designed as W1 of 13.5 mm, W2 of 18.0 mm, W3 of 22.5 mm, W4 of 27.0 mm, and W5 of 31.5 mm. The mean value of basal crop coefficient (Kcb) at the initial-, mid-, and late-season was 1.00, 1.30, and 0.89, respectively. The Kc-local (ETa/ET0) range for apple orchard with DCHD was 1.11–1.20, 1.33–1.43, and 1.09–1.22 at the initial, middle, and late season, respectively. ETa of apple orchard in this study ranged between 415.55–989.71 mm, and soil evaporation accounted for 13.85–29.97% of ETa. Relationships between total irrigation amount and apple yield and WP were developed, and W3 was suggested as an optimum irrigation schedule with an average apple yield of 30,540.8 kg/ha and WP of 4.45 kg/m3 in 2019–2020. The results have implications in developing irrigation schedules and improving water management for apple production in arid regions.
Highlights
Model performance was evaluated by the root mean square error (RMSE), the average absolute error (AAE), and the Nash–Sutcliffe efficiency index (NSE)
The results indicated that an appropriate irrigation schedule was a benefit to improve water productivity
Evapotranspiration (ETa), yield, and water productivity (WP) of the dwarf cultivation with high density (DCHD)-cultivated apple orchard were investigated with a two-year field experiment
Summary
Field experiments were conducted at a 600-ha apple orchard (40◦ 390 N, 81◦ 160 E, altitude 1011 m.a.s.l) with dwarf stocks and dense planting, located in Alar City, 1st Division of the Xinjiang Production and Construction Corps (Figure 1a), from April to August in 2019 and 2020. The soil type is sandy loam with an average bulk density of 1.51 g/cm and field capacity of 0.185 cm3 /cm at 0–120 cm soil depth. The bulk density was measured by the core method with a solid ring, the field capacity was obtained by the plot irrigation method, and the wilting point was obtained by measuring the soil moisture content under 15 bar by using the pressure membrane meter method. On average of the two growing seasons, soil available N, P, and K contents of the cultivated horizon (0–30 cm) were 10.0, 3.2, and. Groundwater is located at >3.0 m below the soil surface
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