Comparing variability of on-farm greenhouse gas emissions and energy use with the WICST project

Thus far, few studies have estimated greenhouse gas (GHG) emissions, and energy use, modeled by life cycle inventory development (LCID) tools to the individual farm level. The Wisconsin Integrated Cropping System Trial (WICST), an on-station experiment, has provided a unique opportunity to perform LCID’s on cropping systems over a 16 year period and that effort is reported in a sister article in this volume (Posner et al). We propose that the next step is to evaluate on- farm situations to assess system variability from farm to farm and compare the results with the WICST project. In a recent, long-term trial in Eastern Canada, a study of the effects of tillage intensity and crop rotation on GHG emissions (kg CO2 eq ha -1)(Meyer-Aurich 2006) found that crop rotation, specifically the inclusion of legumes into corn-based cropping systems, significantly reduced GHG emissions. For example, the introduction of wheat, underseeded with red clover into a corn-soybean system reduced GHG emissions by 595-700 kg CO2 eq ha-1 yr-1. Chisel plow systems had generally fewer GHG emissions than moldboard plow systems, however the reductions were minor when compared to the effect of crop rotation. Other studies have examined the impacts of different farming systems on energy use (MJ ha-1)(Cruse 2010). In a comparison of 2,3 and 4 year crop rotations over 6 years, the longer rotations of 3 (corn-soybean-wheat) and 4 years (corn-soybean-alfalfa-alfalfa) used generally less energy (MJ ha-1) and were more energy efficient (US $ return per GJ ha-1 fossil fuel energy) than a conventional 2 year corn-soybean rotation. The emergence of these new metrics for evaluating farm performance and their potential role in farm payments, has necessitated a closer look at how well a single site, following Best Management Practices (BMPs) is able to describe cropping systems across multiple sites.

Authors: Richard Gaillard and Joshua Posner