Background/Question/Methods Nitrous oxide (N2O) is an important greenhouse gas and a catalyst of stratospheric ozone decay. Agricultural soils are the source of 75% of anthropogenic N2O emissions globally. Recently, significant attention has been directed at examining effects of conservation management practices on carbon sequestration in agricultural systems. However, limited knowledge is available regarding how these practices impact N2O emissions, especially for organic vegetable production systems. In this context, a three-year study was conducted in a well-drained sandy loam field transitioning to organic vegetable production in the Mid-Atlantic coastal plain of USA to investigate impacts of conservation tillage [strip till (ST) and no-till (NT)] and conventional tillage (CT) [with black plastic mulch (CT-BP) and bare-ground (CT-BG)] on plant available nitrogen (PAN) and N2O emissions. Each year, a winter cover crop mixture (forage radish: Raphanus sativus var. longipinnatus, crimson clover: Trifolium incarnatum L., and rye: Secale cereale L.) was grown and flail-mowed in the spring. Results/Conclusions It was observed that PAN was greater in CT-BP and CT-BG during early growing stage and greater in ST during middle growing season. Nearly 80% of annual N2O-nitrogen (N) emissions occurred during the vegetable growing season for all treatments. Annual N2O-N emissions were greater in CT-BP than in ST and NT, and greater in CT-BG than in NT, but not different between CT-BG and CT-BP, ST and NT, or CT-BG and ST. Conventional tillage promoted N mineralization and plastic mulch increased soil temperature, which contributed to greater N2O-N fluxes. Crop yield was lowest in NT in Year 1 and CT-BP in Year 3 but yield-scaled N2O-N emissions were consistently greatest in CT-BP and lowest in NT each year. The results suggest that for coarse-textured soils in the coastal plain with winter cover crops, conservation tillage practices may reduce N2O emissions in organic vegetables without yield reduction. California, the leading agricultural producing state in US, accounts for over 13% of the nation's total agricultural value. Over a third of the country's vegetables and two-thirds of the country's fruits and nuts are grown in California. Since 2017, California Department of Food and Agriculture, through the state Healthy Soils Program, has provided financial incentives to California growers to implement conservation management practices that improve soil health and reduce atmospheric greenhouse gases (GHGs). Annual GHGs reductions are model estimated from implementation of conservation management practices funded through the program.
