Tracing crop residue N into subsequent crops: Insight from long-term crop rotations that vary in diversity

This study used 15N isotopes for tracing nitrogen turnover of above- and below-ground crop residues and uptake by subsequent crops in a long-term crop rotation experiment. Diversified rotations did not increase transfer of residue-N to subsequent crops. Crops recovered more below-ground residue-N than above-ground residue-N. Indigenous soil N or fixed N were the top contributors to crop N uptake. Fertilizer rates should better account for indigenous soil N, legume N, and below-ground residue-N.