Data for: Declining soil organic matter as a dominant control on agricultural nitrogen loss

Exogenous N inputs (synthetic fertilizers and manure) are often thought to be the leading cause of declining water and air quality and loss of biodiversity. Soil organic matter loss from cropping systems is often underappreciated, although it is by far the largest source of N in agricultural systems. Our results suggest that the change in soil N due to organic matter loss largely influences environmental N loss in intensive cropping systems over three decades. Together with the effective management of synthetic fertilizer and manure, policies and practices that retain or accrue soil organic matter in agricultural systems are crucial for realising water quality goals, reducing gaseous N emissions, and enhancing biodiversity.