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

Document Type: Research Paper

Authors

1 Institute of Protected Agriculture, Chinese Academy of Agricultural Engineering, Beijing 100125, China

2 Key Laboratory of Plant-Soil Interactions, MOE, Center for Resources, Environment and Food Security, College of Resources and Environmental Science, China Agricultural University, Beijing 100193, China.

Abstract

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

Keywords