Nitrogen Dynamics and Greenhouse Gas Emissions In a No-till Chronosequence.

No-till (NT) farming has gained wider acceptance in the US and world agriculture, and has yielded various environmental quality benefits including topsoil retention and carbon sequestration. �However, long-term effects of NT on nitrogen dynamics and greenhouse gas emissions (GHG; CO₂, CH₄, and N₂O) are not well documented. �This study conducted in a NT chronosequence (ranging from 9 to 48 years) under corn-soybean rotation across Ohio examined the effects of NT on GHG emissions and nitrogen dynamics in comparison to conventional tillage (CT) and forest soils. �Preliminary data (September 2009 to May 2010) indicated an increase in CO₂ and N₂O emissions and CH₄ consumption with an increase in NT duration. �Greater CO₂ emissions were recorded at the forest than at the cropland sites with minor differences between tillage treatments. �While CH₄ consumption was observed at almost all the study sites, uptake rate was higher under NT than at the sites under CT. �The difference between tillage practices was even clearer when soil drainage class was considered. �For example, at sites under NT for 48 y, uptake rate at a well-drained site was 10-12 times than that at a poorly-drained site. �At the younger NT sites, N₂O emissions did not differ with CT sites. Soil ammonium-N increased with NT duration, especially at the surface (0-10 cm) soil layer. �In the 0-5 cm layer, nitrate-N was higher under NT than CT in most sites of the chronosequence. �These results will be discussed in relation to the evolution of various soil physical and biological properties under NT farming.�