Effects of nitrogen fertilization on potato tuber yield, N uptake and soil NO3--N accumulation under plastic cover with drip irrigation

A field experiment was carried out to investigate the effects of different nitrogen levels（N0，90，180，270 and 360 kg/ha）on potato tuber yield, soil nitrate accumulation, nitrogen balance and use efficiency in potato under plastic cover with drip irrigation. The results show that the tuber yield of the N180 treatment is the highest, and the highest soil NO3--N contents are observed at 020 cm soil layers of each treatment at the harvest stage of potato, and the soil NO3--N contents are reduced with the increase of depth in soil profiles (0120cm). Soil NO3--N accumulation of each treatment(040cm) accounts for 47.75%53.17% of total accumulation (0120cm). Soil NO3--N accumulation and nitrogen apparent loss are positively correlated with the nitrogen application rates. Potato nitrogen uptakes，Soil NO3--N accumulation and nitrogen apparent loss accounts for 37.93 %, 45.99 % and 16.08 % of the total nitrogen input. N absorption of potato tubers and nitrogen harvest index are increased with the increase of the nitrogen application rate. The highest NRE，NAE and NPE are observed in the treatment of N90，about 67.97%、68.06 kg/kg and 154.92 kg/kg, respectively. The nitrogen application rates should be controlled by 90180 kg/ha under plastic cover with drip irrigation in potato production areas of northern Yinshan mountains in Inner Mongolia.