Effects of residue placement on Co2 loss in an irrigated, no-till corn system

Authors: OLESZAK, HANIA - Colorado State University; COTRUFO, M. FRANCESCA - Colorado State University; Stewart, Catherine

Submitted to: Proceedings of Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/10/2020
Publication Date: 3/10/2020
Citation: Oleszak, H., Cotrufo, M., Stewart, C.E. 2020. Effects of residue placement on Co2 loss in an irrigated, no-till corn system. Proceedings of Great Plains Soil Fertility Conference.

Interpretive Summary: It is well known that crop residue management practices that leave crop residues on the soil surface, such as with no-till agriculture, promote soil productivity. However, the effects of such practices on the storage of atmospheric carbon (C) in the soil as soil organic carbon (SOC) storage are highly variable. To better understand how crop residue management impacts the loss of carbon through microbial mineralization (as CO2 through microbial decomposition), we investigated the effects of residue location and addition on the CO2 produced from residue decomposition under no-till irrigated continuous corn in Northern Colorado. Most C in the soil environment has a molecular weight of 12 (12C). To monitor crop-residue C transformations and movement (flux) in the soil system we tagged crop-residues with a heavy isotope of C (13C). The 13C labeled-crop-residues were both incorporated/mixed into the soil and were applied to the soil surface. Over a period of two years, we monitored the CO2 fluxes of 13C labeled-residue treatments (i.e., incorporated vs surface-applied) and their respective unlabeled-residue controls. Ultimately, our surface-applied treatments lost more residue carbon as CO2 than did our incorporated treatment over this two-year period. Our results suggest that, over the long term, there may be more residue lost as CO2 in irrigated systems practicing no-till agriculture, compared to those that are conventionally tilled.

Technical Abstract: It is well known that residue management practices that leave crop residue on the surface, such as no-till agriculture, promote soil fertility. However, the effects of such practices on carbon sequestration can be highly variable. To better understand how residue management impacts the loss of carbon through mineralization, we investigated the effects of residue location and addition on CO2 produced from residue decomposition under no-till irrigated continuous corn in Northern Colorado. Over a period of two years, we monitored the CO2 fluxes of 13C labeled residue treatments (i.e., incorporated vs surface applied) and their respective unlabeled residue controls. In the first year of the experiment, the incorporated residue treatment had greater residue-derived CO2 loss during the non-growing season, while the surface applied residue treatments lost more residue-derived CO2 during the growing season. In the second year, surface applied residue had greater residue-derived CO2 loss than the incorporated residue in both the non-growing and growing season. Ultimately, our surface applied treatment lost more residue carbon as CO2 (38.06%) than did our incorporated treatment (20.39%) over this two-year period, but still only represented a fraction of the added residue. Our results suggest that there may be more residue lost as CO2 in irrigated systems practicing no-till agriculture, compared to those that are conventionally tilled, over the long term. However, CO2 is only one piece of the carbon puzzle and therefore, the efficiency of carbon stock formation in the soil profile must be investigated as well.