Long-Term Crop Rotation Diversity Effects On Soil C and N

Authors: Schmer, Marty; Jin, Virginia; Wienhold, Brian; VARVEL, GARY - Former ARS Employee

Submitted to: Proceedings Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/3/2020
Publication Date: 3/10/2020
Citation: Schmer, M.R., Jin, V.L., Wienhold, B.J., Varvel, G.E. 2020. Long-Term Crop Rotation Diversity Effects On Soil C and N. Proceedings Great Plains Soil Fertility Conference. Vol 18 pp. 34-40. March 2020 (proceedings)

Interpretive Summary: Long-term effects from crop rotation and soil management practices on soil organic carbon and soil nitrogen stocks provides important information on sustainable cropland management under a changing climate. Quantifying soil organic carbon storage both by soil layer and cumulatively is important in detecting the influence of management on soil organic carbon changes. We investigated how fertilizer rate and crop rotations impact soil organic carbon from a 34-year study located in eastern Nebraska. Seven crop rotations (three continuous cropping systems; two 2-yr crop rotations; and two 4-yr crop rotations) and three N-levels were compared. We took soil samples to a depth of 60 inches. Differences were found in the surface soils (0 to 3 inches) with greater soil organic carbon in the rotations with more than one crop included. Total soil N was greater with increased crop rotation diversity for the 0-12 inch soil profile. Trends in total N stocks were similar to those of SOC stocks. Overall, crop rotation had a larger effect on SOC and N stocks than N fertilizer.

Technical Abstract: The objective of this study was to evaluate the effects of nitrogen (N) fertilizer level and crop rotation diversity on soil organic carbon (SOC) and N stocks from a 34-yr study located in eastern Nebraska. Seven crop rotations (three continuous cropping systems; two 2-yr crop rotations, and two 4-yr crop rotations) and three N levels were compared. Soil samples were taken to a depth of 60-inches. Differences in SOC stocks were largely confined to the 0 to 3-inch depth with greater SOC (P = 0.0002) in rotations than continuous cropping systems and greater SOC (P = 0.0004) in 4-yr vs. 2-yr rotations. Total soil N was greater with increased crop rotation diversity for the 0 to 12-inch soil profile. At the full sampled soil profile (0-60 inches), SOC stocks were similar between N levels and greater for the 4-yr vs. 2-yr crop rotations (P = 0.0492). Trends in total N stocks were similar to those of SOC stocks. Overall, crop rotation had a larger effect on SOC and N stocks than N fertilizer.