Contrasting rhizosphere nitrogen dynamics in Andropogoneae grasses

Abstract

Nitrogen (N) fertilization in crop production significantly impacts ecosystems, often disrupting natural plant–microbe–soil interactions and causing environmental pollution. This study tested the hypothesis that diverse species adapting independently to various environments might exhibit a wide range of rhizosphere nutrient management strategies, and some of them may be conducive to an efficient N economy for crops. We analyzed the N cycle in the rhizospheres of 36 Andropogoneae grass species related to maize and sorghum and observed significant phylogenetic variation among their impacts on N availability and losses. All three annual species examined, including sorghum and maize, function as N ‘Conservationists’, reducing soil nitrification potential and conserving NH₄⁺. In contrast, seven of the assayed perennial species enhance nitrification and leaching (‘Leachers’). Four other species exhibit similar nitrification stimulation effects but limited NO₃⁻ losses (‘Nitrate Keepers’). We complemented the controlled phenotypic evaluation with an evolutionary-ecological analysis of the same species. We identified several soil characteristics associated with the phylogenetic variation in rhizosphere N dynamics across grasses and highlighted the crucial roles of a few transporter genes in soil N management and utilization. In addition to the ecological and genetic insights, these findings offer valuable guidelines for future maize breeding efforts to enhance agricultural N efficiency and sustainability.