Nitrogen is the major nutrient limiting plant growth in terrestrial ecosystems. The transformation of inert nitrogen to forms that can be assimilated by plants is mediated by soil microorganisms. However, global cycling of nitrogen has transgressed a critical threshold: the amount of atmospheric N2 industrially converted into ammonia to produce fertilizers now exceeds that produced from all of the Earth’s terrestrial biological processes. This excess reactive N from fertilizer use poses a threat to soil, water, and air quality due to nitrate leaching and emission of N2O, a potent greenhouse gas. The last decade has witnessed significant advances in understanding of plant-microbe interactions and in this talk, I will illustrates the various routes by which plants actively influence the availability of nitrogen forms in soil through an array of interactions with most nitrogen-cycling microbial guilds. This knowledge is invaluable for improving plant nitrogen acquisition, while minimizing nitrogen inputs and losses in sustainable agricultural systems.