Optimizing irrigation amount and fertilization rate of drip-fertigated spring maize in northwest China based on multi-level fuzzy comprehensive evaluation model

The arid and semi-arid region of northwest China is an important region for spring maize production in China, but improper water and fertilizer management has caused ecological problems in these regions. A two-year field experiment was conducted in 2015 and 2016 in the Gansu Province of China to investigate the effects of different irrigation amounts and fertilization rates on growth, grain yield, water and fertilizer use efficiency, and soil nutrient residue of drip-fertigated spring maize, and explore the optimal combination of irrigation amount and fertilization rate based on a multi-level fuzzy comprehensive evaluation (MFCE) model. The irrigation levels included I 60 (60% of crop evapotranspiration), I 75 , I 90 and I 105 in 2015 and I 60 , I 80 , I 100 and I 120 in 2016. The N-P 2 O 5 -K 2 O fertilization rates (kg ha −1 ) were F 60–30–30 , F 120–60–60 , F 180–90–90 and F 240–120–120 . The results showed that plant height, stem diameter and leaf area index were highest under F 240–120–120 . Maize yield, dry matter, water use efficiency (WUE) followed a upward opening parabola with irrigation amount and fertilization rate, and reached the maximum under I 90 F 180–90–90 in 2015 and under I 100 F 180–90–90 in 2016. With the simultaneous increase in irrigation amount and fertilization rate, nitrate nitrogen content in the 60–120 cm soil layer showed an increasing trend. Based on the MFCE model, the irrigation amount of 415–450 mm combined with the N-P 2 O 5 -K 2 O rate of 144–77–77 to 180–90–90 kg ha −1 obtained the optimal comprehensive benefit of maize growth, economic return, water and fertilizer utilization and environmental benefit. This work can provide a scientific basis for the optimization and management of spring maize irrigation and fertilization in northwest China. • Irrigation and fertilization coupling model was established based on multi-level fuzzy comprehensive evaluation. • Irrigation and fertilization significantly affected maize growth, yield, water use efficiency and soil nutrient residue. • Irrigation amount of nearly 100% ET c and N-P 2 O 5 -K 2 O rate of 180–90–90 kg ha −1 obtained the highest yield, water and fertilizer efficiency.