No-till farming and greenhouse gas fluxes: Insights from literature and experimental data.

Tillage intensity may differently impact gaseous losses of C and N to the atmosphere, but data from long-term experiments are relatively few. Yet, this information is needed to better understand C and N losses and gains in agricultural systems. The objective of this study was to determine how tillage intensity affects soil greenhouse gas (GHG) fluxes (CO 2 , N 2 O, and CH 4) by comparing experimental data from moldboard plow (MP), chisel plow (CP), double disk (DD), and no-till (NT) soils after 38–40 yr of management in a rainfed corn (Zea mays L.)- soybean (Glycine max (L.) Merr) cropping system. We also reviewed global literature to evaluate the impacts of tillage on soil GHG emissions. After 38–40 yr of management, CO 2 fluxes decreased in this order: MP > CP ≈ DD > NT, indicating that as tillage intensity decreased, CO 2 fluxes decreased. Indeed, daily CO 2 fluxes were typically lower under NT than under MP and CP. Similarly, the overall cumulative CO 2 fluxes across 26-mo of measurement were 1.4–1.8 times lower with NT than MP, CP, and DD soils. Also, MP soils had 1.3 times higher CO 2 fluxes than CP and DD soils. These results are similar to those from our global literature review of 60 studies on CO 2 fluxes. The reduction in CO 2 fluxes in NT was likely due to a combination of increased residue cover, reduced soil temperature (r = 0.71; n = 12; p < 0.001), and increased water content (r = −0.75; n = 12; p < 0.001). Daily N 2 O and CH 4 fluxes were highly variable; and cumulative fluxes across the 26-mo study were unaffected by tillage, mirroring findings of our literature review of 37 papers on N 2 O fluxes and 24 on CH 4 fluxes. Overall, based on the data from both the long-term experiment and literature review, NT appears to be the best option to reduce losses of CO 2 followed by reduced till (DD), but N 2 O and CH 4 fluxes do not generally differ with tillage intensity. • Tillage reduced CO 2 fluxes as: moldboard >chisel =double disk>no-till after 40 yr. • Fluxes of CO 2 decreased as tillage intensity decreased. • Tillage systems had minimal effects on N 2 O and CH 4 fluxes. • No-till farming is the top option to mitigate soil C losses as CO 2. [ABSTRACT FROM AUTHOR]