Optimization of fertilizer and drip irrigation levels for efficient potato production based on entropy weight method and TOPSIS

Objective The effects of drip irrigation and fertilizer levels on the growth, yield, quality, water and fertilizer utilization efficiency and economic benefits of potato were studied under fertigation system.

Methods The orthogonal test design method was adopted and total of 10 treatments were setup, including three drip irrigation levels of crop evapotranspiration (ET_C) of 100% (W1), 80% (W2), and 60% (W3); three fertilizer (N-P₂O₅-K₂O) levels of 240-120-300 kg/hm² (F1), 180-90-225 kg/hm² (F2), and 120-60-150 kg/hm² (F3); three potato cultivars of Feiurita (V1), Longshu 7 (V2) and Qingshu 9 (V3); and a no fertilizer control (W3F0V1). The chlorophyll content, net photosynthetic rate and water consumption of potato were measured during growing stage, and the dry matter accumulation, yield, yield components, and quality of potato were determined at harvest. The water use efficiency (WUE), fertilizer partial productivity (PFP), and economic benefits were analyzed and calculated.

Results Irrigation and fertilizer levels affected potato yield components, starch content, vitamin C content, crude protein content, PFP, and net income significantly. F2 treatment had the highest yield, dry matter accumulation, starch content, vitamin C content, crude protein content, and net income, which were 19.28%, 1.13%, 1.62%, 3.79%, 8.79%, 34.64% higher than F1, and 21.48%, 3.07%, 6.27%, 6.08%, 11.18%, 27.94% higher than F3 treatment, respectively. All the above indexes increased with increasing irrigation levels, but the reducing sugar content was the highest under W2. Cultivar Qingshu 9 had higher leaf chlorophyll, starch, crude protein, and vitamin C content, and higher WUE and PFP than the other two cultivars. According to entropy weight method and TOPSIS analysis, the optimum treatment combinations were F2W2V3, F1W1V1 and F3W2V1. Treatment F2W2F3 had the highest yield, tuber weight, commodity potato yield, maximum single tube weight, crude protein content, WUE and net income, which were 49.22 t/hm², 1096.7 g/plant, 794.3 g/plant, 433.9 g, 0.214 mg/g, 20.21 kg/m³ and 44832 yuan/hm², respectively. Treatment F1W1V1 and F3W2V1 ranked the second and the third with the yield 41.79 and 37.67 t/hm², tuber weight 906.5 and 836.7 g, commodity potato yield 711.4 and 607.3 g/plant, maximum tube weight 395.6 and 357.1 g/tube, and net income 34584 and 32023 yuan/hm².

Conclusion The optimum combination of high yield, high quality, high water and fertilizer utilization efficiency and high economic benefits is 80% ET_C and N-P₂O₅-K₂O 180-90-225 kg/hm². Under this water and fertilizer combination, cultivar Qingshu 9 produces higher index values than the other two cultivars in northwest Shaanxi.