Controlled-release urea combined with fulvic acid enhanced carbon/nitrogen metabolic processes and maize growth

BACKGROUND Controlled-release urea (CRU) or fulvic acid (FA), when applied, have been shown to increase nitrogen (N) use efficiency (NUE) or to stimulate plant growth, yet their interactive effects are not well explored. The objective of this study was to investigate the synergistic mechanisms of CRU combined with FA (CRU + FA) on maize (Zea mays L.) growth. Through the experimental design with five treatments, the N metabolism through the transcriptomic analysis of maize leaf, endogenous hormones, photosynthesis enzymes in maize leaf and root, and maize yield and NUE were evaluated. RESULTS Compared with CRU treatment, CRU + FA treatment significantly increased auxin, nitrate reductase, and glutamate dehydrogenase in leaf by 35.4%, 43.9%, 40.8% and 19.5%, respectively, as well as, the relative content of the leaf chlorophyll and photosynthetic rate by 14.8% and 45.6%, respectively, at 12-leaf collar stage; the carbon/nitrogen (C/N) metabolic process was significantly enriched in CRU + FA treatment by 312 and 418 genes, according to transcriptome profiles of C/N metabolic in leaves from various fertilizer treated maize; maize yield and NUE of CRU + FA treatment were increased by 6.3% and 38.4%, respectively. CONCLUSIONS These results demonstrated that CRU + FA is a viable fertilization scheme that can enhance maize growth, yield and NUE through their synergies in improving N uptake, promoting photosynthesis, increasing C/N metabolic processes, and enhancing enzyme activities. (c) 2021 Society of Chemical Industry.

Automated summary

The combination of CRU and FA significantly increased auxin, nitrate reductase, and glutamate dehydrogenase in leaves, as well as the relative content of leaf chlorophyll and photosynthetic rate. The C/N metabolic process was enriched in CRU + FA treatment, and maize yield and NUE were also increased. These results demonstrate that CRU + FA can enhance maize growth, yield, and NUE through improving N uptake, promoting photosynthesis, and enhancing enzyme activities.