The plasticity of root distribution and nitrogen uptake contributes to recovery of maize growth at late growth stages in wheat/maize intercropping

Abstract

Previous studies showed that the competition-recovery principle is one of the mechanisms underpinning overyielding in wheat/maize intercropping. However, few studies have focused on the effects of root morphological and physiological changes during the recovery growth of late-maturing species. The present study aimed to determine the mechanism underlying the recovery growth in terms of root distribution and nitrogen (N) uptake in response to different N supplies. The roots of maize were sampled three times by auger after wheat harvest in the intercropping system with six levels of N application and sole crops at one N-application rate under field condition. Intercropped maize adjusted its root length density (RLD) and root distribution and enhanced its N absorption per unit root length with increasing soil N concentration. Soil inorganic N concentration had a direct influence on RLD of intercropped maize which was related to shoot N concentration. In addition, maize took up 93% more N per unit root length when intercropped with maize compared with sole cropping. Our findings show that the recovery growth of late-maturing species involves phenotypic plasticity of maize root architecture, and the enhanced N uptake resulted from extra soil N acquired from the area where wheat was growing before its harvest.