Multi-objective optimization of water and fertilizer management for potato production in sandy areas of northern China based on TOPSIS

Sandy areas in the northern China are the primary regions for potato production, but limited water resources and low water/fertilizer use efficiency limit the sustainable development of agriculture. Field experiments were conducted during 2016-2017 to investigate the effects of different drip irrigation frequencies, water amounts and fertilizer rates on the yield, quality, water and fertilizer productivity of potato in the sandy areas of northern China. The water and fertilizer treatments were evaluated using the TOPSIS method to obtain the optimal combination of irrigation frequency, water amount and fertilizer rate for multi-objective optimization. The irrigation frequency included once every 4 days (D-4), once every 8 days (D-8) and once every 10 days (D-10). The irrigation levels consisted of full irrigation (1.0 ETc, ETc is the crop evapotranspiration), medium irrigation (0.8 ETc) and low irrigation (0.6 ETc). The fertilizer (N-P2O5-K2O) levels included low fertilization (F-1, 100-40-150 kg ha(-1)), medium fertilization (F-2, 150-60-225 kg ha(-1)) and high fertilization (F-3, 200-80-300 kg ha(-1)). The results showed that there were significant effects of the irrigation frequency (IF), irrigation level (IL) and fertilization level (FL) on potato growth, yield, quality, water and fertilizer productivity. Using the same irrigation frequency and fertilization level, the highest tuber yield, starch content, vitamin C and partial factor productivity (PFP) were obtained under the full irrigation (1.0 ETc). However, the irrigation water use efficiency (IWUE) decreased as the water supply increased. In addition, these indicators under deficit irrigation increased with the increase in irrigation frequency at the same fertilization level, but the indicators of D-8 were the highest under the full irrigation. Under the same irrigation frequency and irrigation level, the tuber yield and IWUE increased as the fertilization rate increased. However, the PFP decreased as the fertilizer rate increased. The trends in plant height, LAI, dry matter accumulation, plant yield and commodity tubers were similar to that in tuber yield. The starch content and vitamin C under deficit irrigation increased with the amount of fertilizer applied, but they increased first and then decreased with the increase in fertilizer rate under the full irrigation. The change in the content of reducing sugars was opposite to that of the starch. Based on the TOPSIS method, the multi-target optimum scheduling of potato was attained with the irrigation frequency of once every 8 days (D-8), full irrigation(1.0 ETc and high fertilizer (N-P2O5-K2O) rate (F-3, 200-80-300 kg ha(-1)). The obtained optimum combination of water and fertilizers can provide a scientific basis for irrigation and fertilization optimization and management in the sandy areas of northern China and in other regions with similar environments.