Experimental study and multi–objective optimization for drip irrigation of grapes in arid areas of northwest China

Grapes are the most important cash crop in Xinjiang. However, the effective utilization of agricultural water and fertilizer in this area is relatively low, which is very unfavourable for the development of Xinjiang grape industry. At present, there is a lack of research based on multi-objective water and fertilizer optimization to guide grape production. Field experiments were thus conducted over three consecutive years (2015–2017) to study the effects of water and fertilizer coupling on the yield, fruit quality, water use efficiency (WUE), fertilizer partial productivity (PFP), and net profits of Vitis vinifera cv. “Frey” grapes in northern Xinjiang. The optimum input range of water and fertilizer for multi-objective optimization were determined by using multiple regression and spatial analysis. Five levels of N–P₂O₅–K₂O (180–225–495, 240–300–660, 300–375–825, 360–450–990, 420–525–1155 kg ha⁻¹) were set up in the experiment, designated F₆₀ %, F₈₀ %, F₁₀₀ %, F₁₂₀ %, and F₁₄₀ %, respectively. Three drip irrigation levels were designated W₆₀ %, W₈₀ %, W₁₀₀ %, accounting for 60 %, 80 %, and 100 % of the ETc (where ETc denotes evapotranspiration under sufficient water supply for crops). The results show that at the same fertilization level, the leaf area index (LAI), vitamin C content, titratable acid, soluble solids content, dry matter yield, grape yield, PFP, and net profit increased with an increase in irrigation. They reached their maximum under full irrigation (W₁₀₀ %). Compared to W₈₀ % and W₆₀ % irrigation levels, the WUE at a full (W₁₀₀ %) irrigation was lower, but the PFP was the highest. The maximum grape bunch weight over three years was 407, 383, and 378 g, respectively. The highest harvest index (HI) was 0.460, 0.425, and 0.416, respectively. When the irrigation range was 334–348 mm and the N–P₂O₅–K₂O fertilization range was 320–400–880∼392–490–1077 kg ha⁻¹, the grape yield, net profit, WUE, vitamin C content, titratable acid content, and soluble solids content of the fruits reached more than 90 % of their maximum values simultaneously. The results of this research provide a scientific reference for water and fertilizer management of drip irrigation in Xinjiang vineyards.