Smart Tillage to Reduce N2O Emissions from Organic Agriculture
Project Director
Armen R. Kemanian
Year Funded
2019
Award Number
2019-51106-30189
Funded Institution
Pennsylvania State University
Grant Program
ORG (Organic Transitions)
USDA NIFA Report (alternate)
Project Overview
Organic grain farmers commonly plow-in a cover crop along with livestock manure to provide nutrients for corn. This practice incorporates large amounts of labile organic carbon (C) and nitrogen (N), which stimulates a burst of microbial activity, creating hypoxic soil conditions that favor formation of the powerful greenhouse nitrous oxide (N2O).
This project aimed to reduce N2O emissions while maintaining productivity through three “smart tillage” techniques: (1) spreading manure after plowing the cover crop (seclusion), (2) mixing flail-mowed cover crops into the top 8 cm of the soil profile before plowing, then spreading manure (dilution + seclusion), and (3) harvesting legume top growth before manure and plowing (removal). Treatments were compared with standard practice (plowing manure + cover together) on triticale, crimson clover, and triticale-clover-pea cover crops in a replicated trial. N2O emissions were monitored during two seasons of corn production after smart tillage and control treatments.
Farmer Takeaways
(1) Tilling cover crops + manure into the soil can lead to N2O emissions of 10 kg N2O-N/ha or more, equivalent in climate impact to the loss of 1,290 lb soil carbon/ha as CO2.
(2) Taking a forage harvest from the cover crop before tillage can partially mitigate N2O.
(3) Grass or grass-legume cover crops may form less N2O than all-legume cover crops.
(4) Interplanting cover crops (ryegrass and/or legumes) into corn at the V6 stage can protect the soil and reduce N leaching, but can compete with corn in warmer climates, causing a 10% yield drag south of 41° north latitude.
Project Outputs
Saha, D., J. P. Kaye, A. Bhowmik, M. A. Bruns, J. M. Wallace, and A. R. Kemanian. 2021. Organic fertility inputs synergistically increase denitrification-derived nitrous oxide emissions in agroecosystems. Ecological Applications 31(7):e02403.
McConnell, C.A., Rozum, R.K., Shi, Y. and Kemanian, A.R., 2023. Tradeoffs when interseeding cover crops into corn across the Chesapeake Bay watershed. Agricultural Systems, 209, p.103684.