Stimulated fine root growth benefits maize nutrient uptake under optimized nitrogen management

Abstract

<span class="fontstyle0">Optimized nitrogen (N) management reduces total N application without sacrificing crop<br />yield. However, the underlining mechanisms have not been well investigated, especially lacking<br />the evidence from roots. Here we performed a two-year field experiment with maize grown<br />under zero-N, conventional N and optimized N applications and examined grain yield, N,<br />phosphorous (P) and potassium (K) uptake and root length in diverse diameter classes. Results<br />showed that both conventional N and optimized N managements significantly increased plant<br />nutrient contents and grain yield compared with zero-N treatment, but no obvious difference<br />was observed between the two N-fertilized treatments. Notably, the response of different<br />nutrients to N application was not synchronous temporally over the growth period, following<br />the order of N first, P second and K last. Though N application generally had minor impact on<br />total root length and root biomass, optimized N regime significantly increased fine root<br />(diameter ≤ 0.2 mm) length compared with conventional N at the eighth leaf emerged stage. The<br />stimulated fine root growth under optimized N management is beneficial for adequate N uptake<br />during the key growth stage, which determines subsequent PK acquisition and final crop yield.<br />Our findings highlight the importance of fine roots in maize NPK uptake and a better<br />understanding of the response of fine roots to changes in N availability may therefore be critical<br />for optimizing N input in maize farming system</span>