Cover crops and soil loosening are key components for managing P and C stocks in agricultural soils

Abstract

Agricultural soils have accumulated phosphorus (P) and lost carbon (C) in the recent decades. Simultaneously, soil structure has been degraded by the large increase in machinery weight. High wheel loads compact the subsoil, resulting in reduced root growth, decreased yields, and hence decreased C inputs and P removals. To reduce the accumulated excess P stock, the P balance should be kept strongly negative for decades, which requires high biomass production. P accumulation in poorly yielding field parts has created local hotspots, often characterized by soil compaction and poor drainage. They may be only 1%–6% of the agricultural landscape area but present a high risk for waterbodies. Identifying and targeting these hotspots for P removal can be a key strategy for mitigating P emissions. Achieving the P removal is most likely to require soil loosening to repair the damage caused by compaction and use of cover crops to mine out the accumulated P. This soil improvement strategy can also be beneficial for C sequestration and crop productivity. This commentary highlights the current status and recent developments in the interactions between compaction, cover crops and P loss to provide a research basis for developing landscape-level strategies.