Seven-year impact of cover crops on soil health when corn residue is removed

Authors: WEGNER, BRIANNA - South Dakota State University; Osborne, Shannon; Lehman, R - Michael; KUMAR, SANDEEP - South Dakota State University

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2017
Publication Date: 2/2/2018
Citation: Wegner, B.R., Osborne, S.L., Lehman, R.M., Kumar, S. 2018. Seven-year impact of cover crops on soil health when corn residue is removed. BioEnergy Research. 11:1-9. https://doi.org/10.1007/s12155-017-9891-y.
DOI: https://doi.org/10.1007/s12155-017-9891-y

Interpretive Summary: Crop residue remaining on the soil surface is important in maintaining soil health and improving soil organic carbon levels. Producers are interested in removing crop residue as possible feedstocks for biofuels, bedding and supplemental feed for livestock. Past research has found that removing plant residue from soil has a negative effect on soil health, however, the addition of cover crops may help alleviate this impact. Research was conducted to assess the effect of incorporating cover crops on soil health with varying removal rates of corn residues. Residue removal occurred at three different residue removal levels. The three residue removal treatments were 1) low residue removal, harvesting only the grain and leaving all other plant materials on the soil surface, 2) medium residue removal, harvesting the grain and then baling a portion of the remaining plant material and removing it from the soil surface and 3) high residue removal, cutting corn stalks 0.15 m from the ground and removing the entire plant portion. Plots were split with a portion of the plot receiving a cover crop and a portion without a cover crop. Results showed that there were a greater amount of aggregates in the smaller aggregate size classes for plots without cover crops and more aggregates in the larger aggregate size classes for plots with cover crops. There was a significant impact of cover crops and residue removal on microbial activity, and the amount of soil organic matter and particulate organic matter. We conclude that cover cropping continued over multiple years can mitigate negative effects of crop residue removal on soil health thus limiting soil erosion and maintaining nutrient cycling activities in the vulnerable period following residue removal.

Technical Abstract: Removing plant residue from soil has been shown to have an adverse effect on soil health; however, the addition of cover crops may help mitigate these impacts. This study was conducted to assess the effect of incorporating cover crops on soil health with varying removal rates of corn (Zea mays L.) residues. Corn was grown in rotation with soybean (Glycine max) in a randomized, split-block design with three different corn residue removal levels (37, 55 and 98% of total above-ground C) as whole plot treatments and the presence or absence of cover crops as the split plot treatment. Soil samples were collected from both crop phases following 7 years of cover crop treatment and subjected to a suite of soil health measurements. In the soybean phase immediately following residue removal, there were significant (P=0.025) increases in the erodible fraction (EF) of soil aggregates and reductions in the stable, larger aggregate fractions. Cover crops mitigated these changes in aggregate distributions in the highest residue removal treatment. Residue removal resulted in a significant decrease in fPOM (P=0.03) while the addition of cover crops increased fPOM levels during the soybean phase (P=0.002). Residue removal significantly (P=0.017) decreased soil microbial enzyme activities while cover crops restored activities in the highest residue removal treatment (P=0.037). We also found higher fungal:bacterial ratios with cover cropping compared to no cover crops. We conclude that cover cropping continued over multiple years can mitigate negative effects of crop residue removal on soil health thus limiting soil erosion and maintaining nutrient cycling activities in the vulnerable period following residue removal.