Taking 7-year-old apple trees (Hanfu) as the test material, an experiment with three irrigation levels including high water (W1, 85%-100%θf, θf was the field water holding capacity), medium water (W2, 70%-85%θf) and low water (W3, 55%-70%θf), and three nitrogen application levels, high (N1, 600 kg·hm-2), medium (N2, 400 kg·hm-2) and low (N3, 200 kg·hm-2), was conducted to investigate the effects of water and nitrogen coupling on photosynthetic characteristics, yield and water and nitrogen utilization of apple trees in mountainous areas under surge-root irrigation (SRI). The results showed that the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs), intercellular CO2 concentration (Ci), leaf instantaneous water use efficiency (WUEi) of apple trees leaves decreased with decreasing nitrogen application rates under the same irrigation amount, but Ci increased. Under the same nitrogen application rate, foliar Pn, Tr, gs and WUEi decreased with decreasing irrigation amount, but Ci increased. The daily average values of Pn and Tr under W1N1 treatment were the largest, while W2N2 treatment had the largest WUEi. Apple yield, irrigation water use efficiency (IWUE) and nitrogen partial productivity (NPFP) were significantly affected by irrigation and nitrogen application. The W2N2 treatment had the highest yield (26761 kg·hm-2). IWUE increased significantly with the decreasing irrigation and the increasing nitrogen application, while NPFP increased significantly with the increases of irrigation and the decreases of nitrogen application. Results of the regression analysis showed that the combination of irrigation and nitrogen application was closest to W2N2 treatment when yield and IWUE got the optimal solution. Therefore, W2N2 treatment was the best combination mode of water and nitrogen application for apple under SRI in Northern Shaanxi mountain area.
以陕北山地7年生‘寒富’苹果树为试验材料,设置3个灌水水平[高水(W1,85%～100%θf,θf为田间持水量)、中水(W2,70%～85%θf)、低水(W3,55%～70%θf)]和3个施氮水平[高氮(N1,600 kg·hm-2)、中氮(N2,400 kg·hm-2)、低氮(N3,200 kg·hm-2)],研究涌泉根灌条件下水氮耦合对山地苹果树光合特性、产量和水氮利用的影响。结果表明: 相同灌水条件下,随着施氮量的减少,苹果树叶片的净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(gs)和瞬时水分利用效率(WUEi)降低,但胞间CO2浓度(Ci)增加;相同施氮条件下,随着灌水量的减少,叶片Pn、Tr、gs和WUEi降低,而Ci增加。W1N1处理的Pn、Tr日均值最大,但与W1N1处理相比,W2N2处理的WUEi最大。苹果产量、灌溉水利用效率(IWUE)和氮肥偏生产力(NPFP)受灌水和施氮量的显著影响,W2N2处理的产量最高(26761 kg·hm-2),减小灌水量和增大施氮量使IWUE显著提高,而增大灌水量和降低施氮量使NPFP显著增加。回归分析表明,产量和IWUE同时获得最优解时,灌水量和施氮量组合最接近W2N2处理。因此,W2N2处理为涌泉根灌条件下陕北山地苹果最佳的水氮组合模式。.
Keywords: mountain apple; photosynthetic characteristics; surge-root irrigation; water and nitrogen use efficiency; water-nitrogen coupling; yield.