Effects of different nitrogen rates on potato yield and nitrogen use efficiency in a typical black soil

Objectives The situation of unbalanced nutrient application in potato production in China is serious, and excessive nitrogen application is disadvantagous to agricultural sustainable utilization and ecological environment protection. In this study, the effects of different nitrogen application rates on potato yield, nutrients uptake and nitrogen use efficiency were studied to provide a scientific support for rational fertilization of potatoes based on Nutrient Expert (NE) system.

Methods In this study, two field trials were conducted in different plots in Keshan, Heilongjiang Province during 2017–2018, respectively. Six different nitrogen rates were set up based on the NE system, including no nitrogen fertilizer (N₀), N rate based on NE system decreased by 50% N rate (N₉₀) and 25% N rate (N₁₃₅), NE-recommended N rate (N₁₈₀), N rate based on NE system increased by 25% N rate (N₂₂₅) and 50% N rate (N₂₇₀) . Potato yield, nutrient uptake, and fertilizer utilization efficiencies were measured.

Results In both 2017 and 2018, the potato yield was highest in N₁₈₀ treatment recommended by NE, with an average increase of 40.4% compared with that in N₀ treatment for two years. When N rate was ≤ 180 kg/hm², the potato yield increased with the nitrogen rate increased; when nitrogen rate was > 180 kg/hm², potato yield didn't continue increasing with N rate increased. Compared with N₀ treatment, the averaged increase of nitrogen uptake by tuber, straw and whole plants in N₁₈₀ treatment during 2017–2018 were 49.8%, 58.2% and 52.0%, respectively; correspondingly, the averaged increase of the phosphorus uptake were 36.3%, 52.2% and 39.8%, as well as those of the potassium uptake were 26.4%, 46.8% and 31.3%, respectively. The demand of N, P and K was 4.6, 1.1 and 5.8 kg per ton potato fresh weight, respectively. The potato yield and uptake of N, P and K in N₁₈₀ treatment were the highest. And the N agronomic efficiency and recovery efficiency in N₁₈₀ treatment were not significantly different from those in N₉₀ and N₁₃₅ treatments.

Conclusions Rational application of nitrogen fertilizer can significantly increase potato yield and nitrogen uptake, and increase nitrogen use efficiency when N rate does not exceed N demand in potato. NE system can recommended N rate scientificly, ensure potato yield and improve N fertilizer efficiencies.