There is a global need to increase yields in agroecosystems while minimizing environmental impacts such as trace gas emissions and nitrogen pollution. One of the hurdles we face in our efforts to meet this goal is how do we accumulate soil carbon and simultaneously supply soil organic matter-derived nitrogen to reduce inorganic fertilizer inputs. In this presentation, we show the vital role that soil biodiversity must play to accomplish this objective. Soil biodiversity promotes the formation of soil structure and the efficient decomposition of organic matter and deposition of microbial necromass in mineral associated organic matter. We focus on two specific areas. First, we use recent evidence to argue that N availability is an emergent property of the integrated soil biogeochemical system and is strongly influenced by soil biodiversity and its interaction with plant traits and minerals. Building upon this, we theorize that soil biodiversity increases ecological complexity and the pathways by which plants can access N, creating increasingly resilient nutrient supplies in a variable climate. Second we provide evidence from multiple studies that soil biodiversity is critical to building both carbon and nitrogen in the mineral associated pool. With increased reliance on this pool to supply nitrogen to crops, we can minimize environmental losses and provide just enough external nitrogen to promote modest continuing soil carbon accumulation. We highlight possible interventions to manage soil biodiversity to maximize agroecosystem nitrogen use efficiency and soil carbon accumulation.
