GHG mitigation potentials in the U.S. Corn-Soybean cropping system: Promises and threats from genetically engineered crops, weed resistance and tillage practices
Abstract
There are many reasons why conservation tillage has expanded since the 1970s on the United States cropped acres, but one major reason has been the advent of herbicide resistant crops by genetic improvement. Tillage to control weeds is unnecessary when herbicides can be sprayed over the growing crop but the specific technology was not sustainable in the long run as weed resistance emerged to the main chemical used, glyphosate. Evidence to date suggests that partial reversion to conventional tillage has resulted. However, it remains unknown on how herbicide-tolerant crop adoption, weed resistance and the resultant tillage intensity change have affected greenhouse gas (GHG) fluxes in the U.S. corn-soybean cropping system over the past decades. Using the data of genetically engineered crops (corn and soybean) provided by USDA Economic Research Service, herbicide resistant weeds obtained from International Survey of Herbicide Resistant Weeds, and time-series tillage maps developed from a private survey conducted in U.S. corn and soybean farmers, here we examined how and why tillage intensity has changed across the nation from 1998 to 2016. Then in combination with input drivers of climate change, land use and agricultural management history, the time-series geospatial maps of tillage practices have been used to force a process-based land ecosystem model to quantify the historical GHG mitigations during cultivations. We found that the benefit of herbicide-tolerant crop adoption in reducing tillage has declined and Glyphosate weed resistance is found to drive the intensifying tillage practices, tillage intensity is anticipated to continue increasing which would further stimulate GHG emissions and contribute to climate change.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB068...05L
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0469 Nitrogen cycling;
- BIOGEOSCIENCES;
- 0490 Trace gases;
- BIOGEOSCIENCES