Deep Soil Carbon after 44 Years of Tillage and Fertilizer Management in Southern Illinois Compared to Forest and Restored Prairie Soils.

No-tillage management can reduce soil erosion and increase soil carbon in agricultural systems, but there is less certainty regarding deeper soil and how long-term tillage and fertilization practices compare to other land-use systems. The objective of this study was to quantify tillage and fertilizer management effects after 44 years [20 years in continuous corn (Zea mays L.) and 24 years in corn-soybean (Glycine max L.) rotation] on bulk density and soil carbon stocks to a one meter depth in a somewhat poorly drained Bethalto silt loam near Belleville, IL and compare to nearby forest and restored prairie soils. Four tillage (moldboard plow, chisel tillage, alternate tillage, and no-till) and five fertilizer (no fertilization, N-only, N+NPK starter, NPK+NPK starter, and NPK broadcast) treatments showed bulk density was lower in no-till than moldboard plow treatments in 0 to 15 and 25 to 50 cm depths. Complete NPK treatments generally resulted in higher C stocks than N-only and Control treatments from 0 to 25 cm, but no differences were detected from 25 to 100 cm or 0 to 100 cm due to fertilizer. No-till management increased carbon stocks compared to tillage treatments for 0 to 15 cm and was greater than the ChT treatment for 0 to 100 cm. No-till/ NPK maintained greater cumulative soil carbon stocks to one meter than either undisturbed forest soils or restored prairie soils. Additionally, No-till/NPK had the maximum soil carbon increase over time of 0.36 Mg C ha^-1 y^-1 for the top 15 cm over 44 years.