Field-scale Cropland Soil N2O Emissions as Influenced by Crop Diversification and Cover Crops over Two Years using a Micro-meteorological Method

Abstract

Cropland soil is a major driver of global N2O emissions and crop diversification and use of cover crops (CC) has potential to mitigate these emissions. This two-part thesis study reports on firstly effects of fall cultivation and cover crops on N2O fluxes over freezing and thawing periods in the 2018-19 six-month non-growing season (NGS), and secondly on overall effects of cover crop integrated diversification on N2O fluxes measured on a simple (corn-soybean-soybean) and a diversified (corn with CC-soybean-winter wheat) rotation field between 2018 and 2020. Over the 2018-19 NGS, fall cultivation or cover crops alone increased N2O fluxes, and cultivating summer-established cover crops increased the fluxes even more. Over two years, termination of cover crops resulted in significantly higher growing-season N2O fluxes and 1.67 kg N ha-1 higher total emissions than the simple field over two years. The trends for diversified rotations observed here need to be confirmed in the long-term.