Effects of irrigation and fertilization regimes on tuber yield, water-nutrient uptake and productivity of potato under drip fertigation in sandy regions of northern China

The knowledge of seasonal nutrient demand is necessary for maximizing potato yield and resources use efficiency under drip fertigation, and it also can effectively mitigate the risk of nutrient leaching caused by excessive fertilization. To explore the coupling effects of irrigation level and fertilization rate on drip-fertigated potato growth, nutrient accumulation and determine the multi-objective optimal irrigation and fertilization regimes, a two-year (2018 and 2019) field experiment was conducted in the sandy regions of northern China. The experiments included three irrigation levels (I60, 60% ETC; I80, 80% ETC and I100, 100% ETC, where ETc is the crop evapotranspiration) and five fertilization rates (N0P0K0, 0 kg ha-1; N1P1K1, 100-17.5-124.5 kg ha-1; N2P2K2, 150-26.2-186.7 kg ha-1; N3P3K3, 200-34.9-248.9 kg ha-1 and N4P4K4, 250-43.7-311.2 kg ha-1, where the ratio of N, P and K was 1:0.17:1.24). The results showed that N, P and K accumulated rapidly from 42th to 95th, 50th to 96th and 46th to 91th days after sowing, respectively. For producing 1000 kg tuber yield, the required amounts of N, P and K were 1.97-4.16 kg, 0.55-0.81 kg and 4.83-7.65 kg, respectively. The uptakes of N, P and K in 1000 kg tubers across all treatments were 1:0.18-0.34:1.61-2.59, with the average N:P:K ratio of 1:0.23:2.05. Besides, irrigation level, fertilization rate and their interaction had significant effects on potato leaf area index, biomass, N, P and K accumulation. Deficit irrigation reduced seasonal LAI, biomass, N, P and K accumulation, tuber yield and apparent fertilizer recovery (AFR), but increased water productivity. High fertilization rate was conducive to promoting nutrient absorption, plant growth and improving tuber yield, while it reduced the unit nutrient productivity. The AFR increased first and then decreased with the increase of fertilization rate. To simultaneously achieve high potato yield and resources use efficiency, a multi-objective optimization model was established using the binary quadratic regression analysis between tuber yield, net income, water productivity, AFR and water-fertilizer regimes, which showed that tuber yield, net income, water productivity, and AFR could obtained & GE; 90% of their maximum values simultaneously when the irrigation interval was 204-262 mm and fertilization (N-P-K) interval ranged from 200-24-248 to 247-42-306 kg ha-1. The findings can provide useful information for optimizing irrigation and fertilization regimes in sandy regions of northern China.