Growing concerns about environmental impacts of dairy farms have driven producers to address greenhouse gas (GHG) emissions and nitrogen (N) losses from soil following land application of dairy manure. Tannin dietary additives have proved to be a successful intervention for mitigating GHG and ammonia (NH3) emissions at the barn scale. However, it is unknown how land application of dairy manure from cows fed tannin diets affects crop–soil nitrogen dynamics and soil GHG flux. To test this, cows were fed diets at three levels of tannins (0.0%, 0.4%, and 1.8% of dry matter intake) and their manure was field applied at two N rates (240 and 360 kg N ha−1). Soil NH4+‐N, NO3−‐N, corn silage yield, and soil GHG flux were then measured over a full growing season. Soils amended with tannin manure had lower initial NH4+‐N concentrations and lower total mineral N (NH4+‐N + NO3−‐N) concentrations 19 days after application, compared to soils amended with no tannin manures. Despite lower early season N availability in tannin‐fertilized plots, there were no differences in corn silage yield. No differences in soil GHG and NH3emissions were observed between manure‐amended treatments. These results demonstrate that while tannin addition to dairy cow feed does not offer short‐term GHG or NH3emissions reductions after field manure application, it can promote slower soil N mineralization that may reduce reactive N loss after initial application.
Meeting ambitious climate targets will require deploying the full suite of mitigation options, including those that indirectly reduce greenhouse-gas (GHG) emissions. Healthy diets have sustainability co-benefits by directly reducing livestock emissions as well as indirectly reducing land use emissions. Increased crop productivity could indirectly avoid emissions by reducing cropland area. However, there is disagreement on the sustainability of proposed healthy U.S. diets and a lack of clarity on how long-term sustainability benefits may change in response to shifts in the livestock sector. Here, we explore the GHG emissions impacts of seven scenarios that vary U.S. crop yields and healthier diets in the U.S. and overseas. We also examine how impacts vary across assumptions of future ruminant livestock productivity and ruminant stocking density in the U.S. We employ two complementary land use models—the US FABLE Calculator, an agricultural and forestry sector accounting model with high agricultural commodity representation, and GLOBIOM, a spatially explicit partial equilibrium optimization model for global land use systems. Results suggest that healthier U.S. diets that follow the Dietary Guidelines for Americans reduce agricultural and land use greenhouse gas emissions by 25–57% (approx 120–310 MtCO2e/y) and pastureland area by 28–38%. The potential emissions and land sparing benefits of U.S. agricultural productivity growth are modest within the U.S. due to the increasing comparative advantage of U.S. crops. Our findings suggest that healthy U.S. diets can significantly contribute toward meeting U.S. long-term climate goals for the land use sectors.
more » « less- Award ID(s):
- 2019435
- NSF-PAR ID:
- 10381735
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Sustainability Science
- Volume:
- 18
- Issue:
- 1
- ISSN:
- 1862-4065
- Page Range / eLocation ID:
- p. 539-556
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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