Cropping system partially offsets tillage-related degradation of soil organic carbon and aggregate properties in a 30-yr rainfed agroecosystem

Authors: Jin, Virginia; Wienhold, Brian; Mikha, Maysoon; Schmer, Marty

Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2021
Publication Date: 2/28/2021
Citation: Jin, V.L., Wienhold, B.J., Mikha, M.M., Schmer, M.R. 2021. Cropping system partially offsets tillage-related degradation of soil organic carbon and aggregate properties in a 30-yr rainfed agroecosystem. Soil and Tillage Research. 209. Article e104968. https://doi.org/10.1016/j.still.2021.104968.
DOI: https://doi.org/10.1016/j.still.2021.104968

Interpretive Summary: Long-term agronomic studies provide valuable information on how soils respond to conservation management practices such as tillage and crop rotation. Here, we assessed the effects of 30 years of management using six different tillage treatments and three cropping systems on the soil physical properties involved in wind and water erosion. The tillage practices, in order of increasing intensity, were no-till, ridge till, disk till, subsoil rip, chisel plow, and moldboard plow. The cropping systems included continuous corn, corn-soybean rotation, and continuous soybean. We found that after 30 years, soils responded independently to tillage or to cropping system type. As tillage practice increased in aggressiveness, wind and water erosion risks increased. Even though the use of continuous or rotated corn increased the amount of biomass returned to soils, other crop-related management practices related to corn production introduced additional soil disturbance through N fertility practices (i.e. injection of fertilizer) which tended to counteract the benefit of greater biomass inputs on soil erosion risk. Nonetheless, the management system that conferred the greatest benefit for erosion protection was no-till continuous corn followed by no-till corn-soybean rotation.

Technical Abstract: Soil tillage increases the susceptibility of agricultural soils to erosion and organic carbon losses, but tillage effects could be mitigated through other management practices such as crop rotation. Here, we evaluated the 30-year impacts of tillage intensity and cropping system on surface soil bulk density, nutrient availability, dry aggregate size distribution, and water-stable aggregation. This study was established in 1980 in eastern Nebraska USA, and included six tillage treatments of varying intensity (no-till, ridge till, disk till, subsoil rip, chisel plow, moldboard plow) and four crop rotation treatments (continuous soybean [Glycine max (L.) Merr.]; soybean-corn [Zea mays L.]; corn-soybean, continuous corn) in a randomized block design with six replicates. Surface soils were sampled in 2011 and soil aggregate properties assessed, including occluded particulate organic matter (oPOM) in micro/macroaggregates (0.053–0.5 mm) and mega-aggregates (>2.0 mm). After 30 years, only the main effects of tillage and crop rotation were significant for most measured soil properties. Surface soil organic carbon (SOC) stocks (equivalent soil mass to ~30 cm soil depth) decreased with tillage intensity, and stocks were higher when corn was included in the cropping system. Dry aggregate size distributions shifted towards smaller size classes as tillage intensity increased and whenever corn was included in the cropping system. As a result, aggregate mean weight diameters (mm) followed a similar trend. Soil stocks of water-stable mega-aggregates also decreased with increasing tillage intensity. In near-surface soils (0-7.5 cm), micro/macro-aggregate oPOM was highest in no-till soils and was more sensitive to tillage disturbance (56% to 69% loss) than mega-aggregate oPOM (5% to 35% loss). Even in no-till soils, micro/macro-aggregate oPOM concentrations decreased under continuous corn compared to rotated systems likely due to greater frequency of fertility management-related soil disturbances (i.e. fertilizer injection annually vs every two years). These results suggest that cropping systems that maximize plant carbon inputs can partially mitigate soil erosion risks due to long-term tillage, but that other crop management-related soil disturbances (i.e. method of fertilizer application) could limit the mitigating effect of cropping system.