ABSTRACT
A two-year field and micro-plot 15N-labelled experiment was conducted under two levels of N application rate (240 and 180 kg N ha–1) with three basal N application stages [seeding (L0), four-leaf stage (L4), and six-leaf stage (L6)] to investigate the effects of reducing basal N application amount and postponing basal N fertilization period on wheat growth and N use efficiency (NUE). No significant differences were observed in grain yield, root growth and root morphology between the N180L4 and N240L0 treatments, while the root-shoot ratio of N180L4 was significantly improved. Postponing basal N application period increased the residual basal 15N in soil and reduced basal 15N loss, and N180L4 treatment favored the highest 15N recovery efficiency (NRE), mainly due to reduced 15N loss. Grain yield and basal NRE were significantly positively correlated with root dry weight in deeper soil layers (40–60 cm), and the contribution of root growth to improved grain yield and NRE increased with the downward distribution of the roots. Therefore, postponing the basal N fertilization period under N deficiency promotes deeper root growth during the post-jointing period and increases basal N uptake, as well as reducing basal N loss and increasing grain yield and NUE.
Acknowledgements
We acknowledge the support from the Jiangsu Collaborative Innovation Center for Modern Crop Production (JCIC-MCP).
Disclosure statement
No potential conflict of interest was reported by the authors.