基于产量和品质的陕北苹果滴灌水量和追施氮量优化研究

通过2 a田间试验，研究陕北黄土高原沟壑区滴灌水量和追施氮量对苹果生长指标、产量和品质的影响，优化苹果灌水量和追施氮量，以达到节水、节肥和高产优质的目的。试验设置4个灌溉水平：高水（W₁：100%I，I为计算灌水量）、中水（W₂：80%I）、低水（W₃：60%I）和不灌水W₄，各处理追施氮量均为230 kg·hm^-2（N₂），探究最优灌水量；设置4个追施氮水平：高氮（N₁：施纯氮0.69 kg·棵^-1，约合345 kg·hm^-2）、中氮（N₂：施纯氮0.46 kg·棵^-1，约合230 kg·hm^-2）、低氮（N₃：施纯氮0.23 kg·棵^-1，约合115 kg·hm^-2）和不施氮N₄，各处理灌水量均为80%I（W₂），探究最优追施氮量。试验结果表明，灌水量和追施氮量对苹果生长、产量和品质影响显著。W₁N₂、W₂N₂和W₃N₂处理2 a平均叶片相对含水率比W₄N₂分别增加了7.5%、6.3%和2.5%，各追施氮处理的追施氮量对叶片相对含水率影响不显著。叶片SPAD值随生育期的变化呈现出先增加后减小的趋势，2 a的SPAD值均在W₁N₂处理取得最大值，平均为61.30。W₂N₂处理能显著增加横径70~80 mm和＞80 mm的苹果产量和苹果总产量，提高优果率。W₁N₂处理2 a的单果重均最大，平均为212.86 g，W₂N₂处理的单果重为210.20 g，与W₁N₂无显著差异。W₂N₂处理维生素C含量在2 a间均取得最大值，平均为5.6 mg·（100g）^-1，比W₁N₂增加2.7%，比W₂N₁增加11.6%。W₁N₂、W₂N₂和W₃N₂处理2 a平均可溶性固形物分别比W₄N₂处理减少11.3%、4.9%和2.5%，W₂N₁、W₂N₂、W₂N₃处理2 a平均可溶性固形物分别比W₂N₄处理减少11.7%、9.7%和4.8%。W₁N₂处理平均可溶性糖含量为11.53%，仅比W₂N₂增加2.4%。2年W₁N₂处理的可滴定酸均为最小，平均为0.35%，与W₂N₂处理不存在显著差异。全面考虑果树生长、产量、品质及节水节肥等因素，W₂N₂处理为该研究区较优的苹果灌水和追施氮策略。

Optimization of drip irrigation and topdressing nitrogen based on apple yield and quality in Northern Shaanxi

In order to explore the optimal scheme of drip irrigation (W) and nitrogen (N) application for apple, A two\|year (2017 and 2018) field experiment was conducted to evaluate the effects of different irrigation and N fertilization on growth, yield, and quality of apple. There were four irrigation levels (W₁: 100%I; W₂: 80%I; W₃: 60%I; and W₄: 0) and four N levels (N₁: 345 kg·hm^-2; N₂: 230 kg·hm^-2; N₃: 115 kg·hm^-2; and N₄: 0). The results showed that the irrigation and the topdressing nitrogen had significant effects on the growth, yield and quality of apple. Compared with W₄N₂, the average leaf relative moisture content of W₁N₂, W₂N₂, and W₃N₂ treatments increased by 7.5%, 6.3%, and 2.5%, respectively, and the effect of the amount of applied nitrogen on the relative moisture content of leaves in each treatment was not significant. SPAD value showed a trend of increasing firstly and then decreasing with the growth stages, the SPAD value of 2 years reached the maximum value in W₁N₂ treatment, with an average of 61.30. The W₂N₂ treatment significantly increased apple yield in transverse diameter of 70~80 mm and > 80 mm, total apple yield, and fruit quality. The average weight of single fruit was 212.86 g for 2 years by W₁N₂ treatment while that was 210.20 g by W₂N₂ treatment, showing no significant difference between the 2 treatments. In 2 years, vitamin C content reached the maximum value of 5.6 mg·100g^-1 in W₂N₂ treatment, which was 2.7% higher than that with W₁N₂ and by 11.6% than that with W₂N₁. Compared with W₄N₂ treatment, the average soluble solids of W₁N₂, W₂N₂, and W₃N₂ treatments decreased by 11.3%, 4.9%, and 2.5%, respectively, while that of W₂N₁, W₂N₂, and W₂N₃ treatments decreased by 11.7%,9.7%, and 4.8%, respectively. In 2 years, the average of soluble sugar content of W₁N₂ treatment was 11.53%, only 2.4% higher than that of W₂N₂ treatment. The titratable acids in the treatment with W₁N₂ in 2 years were the smallest, with an average value of 0.35%, which was not significantly different from that treated with W₂N₂. Considering the factors of fruit growth, yield, quality, water saving,and fertilizer, the W₂N₂ treatment was the best combination for apple irrigation and N application in the study area.