Fragipan Remediation Using Annual Ryegrass Cover Crop

Abstract

Field experiments were conducted involving annual ryegrass with and without several surface-applied amendments. The results suggest a significant degradation effect of annual ryegrass on the fragipan horizon. Annual ryegrass (ARG) used as a cover crop was found to degrade previously compacted sections of fragipan, with its roots penetrating through the upper part of the fragipan by first exploring inter-prismatic gray veins and eventually invading adjacent compacted zones, thus creating avenues for additional crop root penetration and utilization of additional water and nutrients. The fragipan structure degradation increased with each (ARG) planting season, resulting in an increasingly deeper soil suitable for crop utilization. Significant crop yield responses of soybean and corn to these soil matrix improvements were observed after the fourth year of using (ARG) as a cover crop and continued to increase yearly thereafter. The yearly addition of sodium, potassium or calcium nitrate fertilizer, or humate additive, did not result in a significant synergistic crop yield effect, but the observed trend in rooting depth warrants further study.