Effects of nitrogen application rates on root recover growth of maize after waterlogging

Aims The growth and development of the root system are of critical significance for crop yield and nutrient utilization. Nitrogen fertilization is frequently utilized to modulate and augment plants' tolerance to abiotic stresses. This study aimed to investigate the effects of nitrogen fertilization on the recovery growth of maize (Zea mays L.) roots and their correlations with grain yield and nitrogen use efficiency after waterlogging stress. Methods A two-year experiment was conducted to examine effects of nitrogen fertilizer application rates (0, 90, 180, 270, and 360 kg N ha-1, designated as N1, N2, N3, N4 and N5, respectively) on root morphological and physiological characteristics under well-watered (W1) conditions across the maize grown season and waterlogging for 6 days at the sixth leaf (V6) growth stage (W2). Results In comparison to W1, W2 significantly decreased length, dry weight, surface area, volume, oxidation activity, zeatin + zeatin riboside, and indole-3-acetic acid contents in roots at the tasselling, filling, and maturity stages regardless of nitrogen rates. Furthermore, these parameters increased with the increase in nitrogen rates (up to N5) under W2, indicating that a high nitrogen rate (such as N5) could enhance the root recovery growth of maize after early(V6)-stage waterlogging. Moreover, the N5 led to a more developed root system, contributing to the improved nitrogen use efficiency under the W2 condition. Conclusion Collectively, a high nitrogen application rate (N5) promoted root recovery growth after waterlogging at the V6 stage, and thus obtained relatively high grain yield and nitrogen use efficiency in maize.