Contrasting rhizosphere nitrogen dynamics in Andropogoneae grasses

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.