Effects of Agronomic Management on GHG Emissions and Soil Carbon Stocks.

The emissions of N2O and CH4 from agriculture contribute to climate change, whereas the emission of CO2 from agriculture can contribute to climate change (net loss of soil organic matter), mitigate climate change (carbon sequestration), or be neutral with respect to climate change. The emission of all three gases is affected by agricultural management, but because a measure may have opposing effects, the net effect of a measure or set of measures is hard to quantify. The objective of this work was to evaluate the effect of several plausible measures on direct emission of greenhouse gases. We focused on arable farming and on those measures (changes in agricultural management) that aim to reduce N2O, CH4 and (net) CO2 emission - for example, greater reliance of manures (at the expense of mineral fertilizers), incorporation of crop residues, fermentation of manure, and catch crops. Because these changes involve selection and optimal distribution of fertilizers and manures, we used Nutmatch, a mixed-integer linear-programming model, to model farmers’ decisions about selection and distribution of fertilizers and manures. We present model results on direct emissions of greenhouse gases under several scenarios along with emissions resulting from the use of fuel, fertilizers and other supplies.