Thirteen-year stover harvest and tillage effects on soil compaction in Iowa

Authors: Phillips, Claire; TEKESTE, MEHARI - Iowa State University; EBRAHIMI, ELNAZ - Iowa State University; Logsdon, Sally; Malone, Robert - Rob; O'Brien, Peter; Emmett, Bryan; Karlen, Douglas

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2023
Publication Date: 4/19/2023
Citation: Phillips, C.L., Tekeste, M., Ebrahimi, E., Logsdon, S.D., Malone, R.W., O'Brien, P.L., Emmett, B.D., Karlen, D.L. 2023. Thirteen-year stover harvest and tillage effects on soil compaction in Iowa. Agrosystems, Geosciences & Environment. 6(2). Article e20361. https://doi.org/10.1002/agg2.20361.
DOI: https://doi.org/10.1002/agg2.20361

Interpretive Summary: Improvements in corn genetics and corn farming practices over time have led to increasing amounts of non-grain plant parts, also called corn stover. Large quantities of corn stover can be difficult for farmers to manage because they interfere with tillage and planting equipment. However, corn stover is also a resource that can be used for animal bedding, low-value feed, bio-products such as fiber board, and cellulosic biofuel. Harvesting stover can potentially provide a source of farm revenue, but it can also potentially degrade soil by reducing soil organic matter and by increasing traffic compaction due to more field traffic and heavier loads. This study evaluated whether stover removal had increased compaction after a 13 year field trial that included both no-till and chisel-plow tillage practices and three levels of stover harvest (none, moderate, and high levels). The chisel-plow practice had evidence of traffic compaction where stover was harvested, with greater compaction in areas experiencing regular wheel traffic compared to areas with minimal wheel traffic. Plots with no stover harvest had no evidence of traffic compaction, which we attributed to having fewer passes from harvest equipment, and possibly due to stover buffering soil from the compactive forces of equipment. The no-till practice had no evidence of traffic compaction, which we attributed to the soil having a higher density and therefore more capacity to bear the loads of farm equipment. The compaction observed when stover was harvested from the chisel-plow treatments did not reduce yields, and furthermore there was no evidence of declines in other soil health indicators such as soil carbon content, bulk density, and soil moisture. We therefore concluded that stover harvest under both no-till and chisel plow management can be implemented sustainably without negative impacts to plant or soil health. These findings are relevant to corn producers interested in sustainable methods of stover harvest.

Technical Abstract: Corn (Zea mays L.) stover is an abundant biomass source with multiple end-uses including animal feed and bedding, bio-products, and cellulosic biofuel production. However, stover removal may potentially increase soil compaction by reducing organic matter inputs and increasing vehicle loads during harvest. While there has been considerable evaluation of stover removal impacts on soil physical quality, few studies have evaluated the role played by traffic compaction. Our objective was to quantify subsurface soil compaction using cone penetration resistance after 13 years of chisel plow versus no-till management and no, moderate (3.5 ± 1.1 Mg ha-1 yr-1), and high (5.0 ± 1.7 Mg ha-1 yr-1) stover harvest rates. Grain yield, soil bulk density, soil water content, and soil organic carbon (SOC) concentration were measured within corn rows, and penetration resistance was measured in trafficked and untrafficked inter-row spaces. Chisel plowed plots with moderate and high levels of stover removal had higher penetration resistance in trafficked areas relative to untrafficked areas, whereas no differences were apparent when stover was retained, suggesting that cumulative effects from fewer wheel passes or buffering impacts of stover retention reduced soil compaction. Traffic compaction did not negatively impact yields, however, and yields were in fact greater with high levels of stover removal compared to no removal. No-till plots had no statistical differences due to wheel-traffic intensity and no evidence of increased compaction with residue removal, indicating a higher load-bearing capacity and less sensitivity to wheel-traffic compaction in no-till soils. Overall, there were no yield-limiting effects of tillage practice or stover removal, and no evidence of soil compaction below the plow layer, suggesting stover removal with both tillage practices can be effectively employed for managing corn stover without detrimental effects on plant or soil health.