Re-thinking soil nitrogen availability to crops in the context of soil organic carbon

The link between carbon and nitrogen (N) in soil organic matter has long been recognized but has been largely ignored in determining the supply of N from soil for crop production. We propose that N mineralization can only be understood as a by-product of soil organic carbon (SOC) change and that progress in improving N use efficiency by crops must explicitly include consideration of SOC. This suggests some immediate avenues for improved fertilizer N management as well as future research activities. Recent advances in understanding the various fractions of soil organic matter and their role in C cycling have great potential for improving our understanding of N cycling in the soil as well, and the potential for N release that could be utilized by crops.