Quantifying improvements in water-stable aggregation caused by corn stover retention

Authors: OJEKANMI, ABIMBOLA - Orise Fellow; Johnson, Jane

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2020
Publication Date: 4/4/2021
Citation: Ojekanmi, A., Johnson, J.M. 2021. Quantifying improvements in water-stable aggregation caused by corn stover retention. Soil Science Society of America Journal. 85(3):776-788. https://doi.org/10.1002/saj2.20198.
DOI: https://doi.org/10.1002/saj2.20198

Interpretive Summary: Corn stover or residue is the leaves, stalk and cob that remains after harvesting corn grain. These materials might be used to make ethanol for use in vehicles or removed for use as animal bedding. Keeping stover on the field is also important for protecting the soil including help form soil aggregates, which are more resistant to be washed away in a rainstorm or during spring thaw. Therefore, it is important to balance removing stover and keeping it on the field. One use of stover is to form aggregates that are less likely to fall apart in water, which are called water stable aggregates. A study was conducted on two fields managed with annual tillage and the other without tillage. On both fields corn and soybean were grown in rotation. When corn was grown, the stover was harvested at four rates, rotation with four rates of corn stover retention treatments [harvesting only grain (Grain), grain plus removing cobs (Grain+Cob), grain plus about half the stover (Grain+Moderate) and grain plus as much stover as possible (Grain+Aggressive)]. Water stable aggregates, their distribution and mean weight diameter were determined on soil collected at 0-2 inches and 2 to 5 inches. Overall, the percentage of water stable aggregates increased by 0.85% and 2.25 % per metric ton of stover returned in the tilled and not tillage fields, respectively. Harvesting stover residue reduced the formation and/or the maintenance of stable aggregates, which implies a reduced ability to resist the erosive force of water. If stover is going to be harvested it is better to remove a moderate amount or less. This information is useful producer and bioenergy producers seeking to balance protecting the soil resource and using a portion of corn stover for energy or other uses.

Technical Abstract: Harvest of corn (Zea Mays L.) stover for bioethanol feedstock or other uses must be balanced against potential degradation of soil properties including water stable aggregates (WSA). The formation and maintenance of WSA is a function of edaphic properties and management. Harvesting stover alters the mass of residue retained, which might alter a soil’s ability to form and maintain WSA. Therefore, a study was conducted on two independently replicated field sites: chisel plow (CP) and no tillage (NT) both with corn/soybean (Glycine Max. L. [Merr.]) rotation with four rates of corn residue retention treatments (RRT) [harvesting only grain (Grain), grain plus removing cobs (Grain+Cob), grain plus about half the stover (Grain+Moderate) and grain plus as much stover as possible (Grain+Aggressive)]. Water stable aggregates, their distribution and mean weight diameter (MWD) were determined on clay loam/loam Mollisol collected at 0-5 and 5-10-cm. Treatments, crop phase, soil depth and interactions were analyzed using a mixed linear model. Linear regression was used to assay relationships between WSA, and the measured average mass of residue returned. In both fields, Grain+Aggressive had the lowest WSA, MWD and fewer aggregates =2-mm compared to other RRTs, and in the NT field fewer in the 1 to 2-mm class size as well. Overall, WSA increased by 0.85% and 2.25 % per Mg stover returned in the CP and NT fields, respectively. Harvesting stover residue reduced the formation and/or the maintenance of stable aggregates, which implies a reduced ability to resist the erosive force of water.