Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Midwest United States is dominated by a two-year corn-soybean crop rotation which has negative effects on soil health. Diversification with novel oilseed crops may help reduce negative effects. Researchers at the ARS in Morris, MN and Brookings, SD evaluated soil aggregation (a soil health measure) as affected by winter and summer oilseed crops compared to standard crop rotations. Soil aggregation is important in resisting soil erosion, with small aggregates and aggregates that break down in water being associated with wind and water erosion. Neither winter nor summer oilseed crops changed the stability of aggregates in water. However, aggregate sizes increased in oilseed treatments and the proportion of small aggregates associated with wind erosion decreased. These findings indicate that the addition of oilseed crops to rotations generate positive improvements in soil health and support development of sustainable agricultural systems through crop diversification.

Technical Abstract: Adoption of oilseeds is expanding in the United States Corn Belt, but their influence on soil aggregation, an indicator for susceptibility to surface wind or water erosion, is scarce. Soil physical properties were measured in rotation treatments of two seasonally different rotation systems: (1) winter oilseeds vs winter fallow and (2) summer oilseeds vs corn (Zea mays L.). Soil was collected from the top 5 cm of both rotations in the fall, following soybean harvest, and separated into six dry aggregate size fractions (DASD) used to calculate the mean weight diameter (MWD), the wind erodible fraction (WEF; 0-1.0 mm aggregates), and the ability of aggregates to remain stable in water (ASW; 1-2 and 2-3-mm aggregates). Winter camelina had a lower WEF (0.22 ± 0.029) compared to winter fallow (0.26 ± 0.029). Summer oilseed treatments had a significant influence on DASD with >50% of aggregates >2 mm in the summer oilseed treatments, and >50% of aggregates >3 mm in the corn treatment. The corn-soybean, Calendula officinalis L.-soybean, and Brassica napas L.-soybean rotations did not differ significantly in MWD (3.59, 3.44, and 3.45, respectively) or WEF (0.20, 0.12, and 0.22, respectively) but had lower MWD and WEF than the Cuphea viscosissima Jacq. X Cuphea lancelota W.T. Aiton-soybean, Echium plantagineaum L.-soybean, and soybean-soybean rotations (MWD: 3.19, 3.23, and 3.22 and WEF: 0.28, 0.26, and 0.25, respectively). Neither winter nor summer oilseeds altered ASW. Nevertheless, MWD and WEF shifts indicates that oilseed crops improved soil aggregation and soil susceptibility to erosive forces of wind.