Localized nutrient supply promotes maize growth and nutrient acquisition by shaping root morphology and physiology and mycorrhizal symbiosis

Localized nutrient supply can induce maize ( Zea mays L.) root proliferation, and then promote nutrient uptake. Yet, how maize plants adjust root morphology, physiology and mycorrhizal symbiosis to efficiently capture nutrients in different heterogeneous environments remains largely unknown. A 2-year field experiment with maize was conducted with localized application of ammonium (N, nitrogen) and phosphorus (P) (LNP); N and P mixed with controlled-release fertilizer (LCF); N and P mixed with organic fertilizer (LOF); diammonium phosphate (LADP) or broadcast N and P application. Our results showed that root length density was 230–584 % larger, root respiration rate was 97–115 % greater, pH value was decreased by 1.61–1.99 units, activity of acid phosphatase activity was 21–36 % higher, mycorrhizal colonization was 19–35 % lower and hyphal length density was 39–69 % lower in localized compared with broadcast nutrient supply. The root morphological and physiological and mycorrhizal fungi responses were tightly associated with improved maize shoot growth and nutrition accumulation. In addition, localized nutrient application at high nutrient rate (e.g. LCP and LOF treatment) had a more strongly positive effect on root proliferation, shoot growth and/or nutrient accumulation compared with broadcast application, especially at later growth stages of maize. Our findings indicate that localized nutrient application can improve nutrient-use efficiency via strengthening positive cooperativity between root morphological and physiological traits, and shaping trade-off between root growth and mycorrhizal symbioses. • Localized application N and P has a positive effect on plant growth and grain yield. • Heterogeneous nutrient supply can enhance fine root growth and rhizosphere process. • Localized application of N and P reduces mycorrhizal colonization and hyphal length. • The intensity and composition of nutrient patch determines the positive effect.