Agronomic and Physiological Response of Potato ( Solanum tuberosum L.) to Nitrogen Fertilization Rate on a Loess Soil of Northwest China

The tuber yield of potato in China is relatively low compared to the average global yield, partly due to poor nitrogen (N) management. Moreover, excessive N fertilization reduces the nitrogen use efficiency ( NUE ) of potato and increases production costs, which reduces profit margins. Therefore, a 2-year field trial was conducted on an existing field with 5 years of different inorganic N fertilization rates in Dingxi to determine the effects of N fertilization rate on growth, tuber yield, net income and NUE of potato on a loess soil. The experiment included six N fertilization rates, namely 0 kg N ha −1 (N0), 75 kg N ha −1 (N1), 150 kg N ha −1 (N2), 225 kg N ha −1 (N3), 300 kg N ha −1 (N4) and 375 kg N ha −1 (N5). The treatments were laid out in a randomized complete block design and replicated four times. The results from the principal component analysis revealed that N fertilization has a strong effect on potato growth, tuber yield and NUE . Treatment N2 increased total tuber yield (29.0% and 33.1%) and net income (54.8% and 61.4%) of potato in 2018 and 2019 seasons, respectively, compared to the control. Excessive N fertilization (N5) reduced tuber yield, net income and NUE of potato in both seasons. To increase tuber yield, net income and NUE of potato (cultivar Qingshu 9) on a loess soil of Northwest China, N fertilization rate should not exceed 150 kg ha −1 .