Tillage and crop rotation impacts on greenhouse gas fluxes from soil at two long-term agronomic experimental sites in Ohio

Soils may be a source or sink of greenhouse gases (carbon dioxide [CO2], nitrous oxide [N2O], and methane [CH4]) that lead to global warming and climate change. While it is known that greenhouse gases are naturally cycled through soil and are part of the carbon (C) and nitrogen (N) cycles, it is not fully understood what effect crop production practices have on this cycling. Therefore, a study was conducted at the longest, continually maintained no-tillage plots in the world at Wooster (50 years no-till), near Wooster, Ohio, and Hoytville (49 years no-till), near Custar, Ohio, that represent two contrasting Ohio soils. Fluxes of greenhouse gases were measured by gas chromatography (GC) biweekly and following rain-fall events greater than 1.2 cm (0.5 in) during the growing season of the corn (Zea mays L.), starting in July of 2011 until October of 2011, and then from May of 2012 to July of 2012. Samples were obtained at both sites in plots with rotations of corn after corn (CC) and corn after soybean (Glycine max L.) (CS), and when soils were managed using no-tillage (NT) and chisel or minimum conservation tillage (MT). Comparisons statistically significant at the p < 0.10 level are as follows. For CO2, the CS rotation yielded lower emissions than the CC at both sites, due to less biomass cycling. For N2O, the CS rotation yielded lower emissions than the CC at both sites due to less total N fertilizer input in the CS than the CC rotation. The NT system resulted in lower N2O emissions than the MT system at Hoytville, but not at Wooster. For CH4, soil in the long-term plots often acted as sinks. Global warming potentials were lower for Hoytville than Wooster and lower for rotation of CS than CC at both Hoytville and Wooster. Overall, after about 50 years, it is evident that the use of no-tillage combined with crop rotations can lead to improved environmental (i.e., greenhouse gas emissions and global warming potential) benefits.