Nitrogen Management for Optimum Potato Yields and Low Environmental Impact in Northwest China

Understanding the changes in nitrate nitrogen (NO₃⁻-N) content in the rooting zone is crucial for reducing nitrate leaching and improving nitrogen (N) use efficiency. The main objective of this study was to investigate the effects of N management strategies on NO₃⁻-N dynamics in the main root zone (0–60 cm) at critical growth stages of drip-irrigated potatoes and to quantify the retention capacity of NO₃⁻-N at harvest in an intensive potato cropping system. Three field experiments with no N application (CK), optimized management (OM) based on a realistic yield goal and soil mineral N content (N_min) and farmer practice (FP) for three potato cultivars were conducted in Inner Mongolia of Northwest China from 2014 to 2016. A total of 52 farmers with over 3000 ha of potato fields were also investigated at harvest. The results showed that OM treatment improved N use efficiency and reduced the environmental risk of N loss while ensuring potato yields compared with FP treatment. Overusing N fertilizer in farmer fields was common, but these N fertilizers only caused a temporary accumulation of NO₃⁻-N during the growing season, then it was reduced to the same level as the optimal treatment at harvest. The NO₃⁻-N retention was about 70 kg ha⁻¹ at harvest in the drip-irrigated potatoes with higher yield, and the data from farmers’ fields confirmed the universality of the NO₃⁻-N retention content. Although retentional NO₃⁻-N content in the main root zone at harvest was similar between FP and OM, obvious accumulation of NO₃⁻-N content was observed during the growing season in FP treatments increasing N loss risk to the environment. The characteristics of soil NO₃⁻-N accumulation in the root zone of drip-irrigated potatoes help to improve management strategies to maximize potato yield while minimizing environmental risks due to N fertilization.