How Does Phosphorus Restriction Impact Soil Health Parameters in Midwestern Corn-Soybean Systems?

Limiting agricultural P losses to surface waters is essential to overall ecological sustainability of agroecosystems. Recent studies have suggested that decreasing P fertilization rates decrease organic matter content, adversely impacting other mitigation strategies. Corn-soy cropping systems from three soil regions of Ohio were subjected to 11 yr of P restriction to measure impacts on soil P availability and agronomic performance as well as both physical and biological indicators of soil health. While both soil P availability and plant tissue P contents decreased with P fertilization rate, crops did not exhibit signs of P stress, such as consistent decreases in corn yield. Organic P levels increased in plots with no P fertilization. Both physical and biological indicators of soil health showed mixed responses to P fertilization, although trends suggested greater organic matter stabilization in unfertilized plots relative to the fertilized plots. This study suggests that reductions in P fertilization can result in more efficient nutrient cycling without adverse agronomic impacts, although it is unclear how long this effect would persist before P restriction would consistently impact grain yields.