5. Conclusion
A complete, LCA-based view of the CO2e savings from tillage
reduction expands the evaluation of emissions on the larger ecological
scale, and focuses the economic analyses on the scale of
representative farm budgets by tillage and across the region. Crop
system models estimate the emissions from agricultural lands providing
insight to changes that accompany tillage reduction under
climate specific conditions. No and reduced-till management of
dryland wheat-based cropping systems are more profitable compared
to conventional tillage in the high and moderate rainfall
zones in the Pacific Northwest temperate climate with 2011
assumptions for crop prices and input costs. In lower rainfall zones,
tillage reduction reduced profits using 2011 prices. Carbon credits
from tillage reduction based on the historically low 2011 value of
$2.48 Mg1 CO2e were too low to compensate growers for replacing
mechanical weed control with herbicides using 2011 fuel and
chemical values in lower rainfall zones.
Reducing tillage intensity both reduces emissions from fuel
usage and increases carbon sequestration under the temperate climate
of the Pacific Northwest region. Sequestered carbon increased
with the increase in yield and recycled biomass in high
Fig. 4. Carbon credit per hectare from tillage reduction and comparison with whole operations budgets.
U. Zaher et al. / Agricultural Systems 122 (2013) 73–78 77
rainfall zones. Nitrous oxide is the main emission sourced by fertilizer
application and a significant component of the GWP of the
wheat-based cropping systems evaluated in this study.
Acknowledgement
This research was supported in part by a Grant from the Paul G.
Allen Family Foundation.