What's Up at the USDA Office?

Upcoming Deadlines/Dates
May 15 – August 1: Primary Nesting Season
July 15: Spring Crop Reporting

Greenhouse Gas Emissions Rise as Tillage Increases
by LuAnn Rolling, District Conservationist

Research has proven that an in increase in tillage increases greenhouse gas (GHG) emissions according to research published in the journal Nature Food in April 2022. Scientists Chaoqun Lu, Iowa State University, Zhen Yu, Nanjing University in China, David A. Hennessy and Hongli Feng, Iowa State University, Hangin Tian, Auburn University and Dafeng Hui, Tennessee State University examined two fluctuations in the recent past of U.S. tillage, a decrease in tillage from the years 1998 to 2008, and a subsequent increase in tillage between 2008 and 2016. The decreases were observed in both carbon dioxide (CO2) and nitrous oxide (N2O). Researchers focused exclusively on tillage practices in corn-soybean rotations.

When tillage was decreasing (from 1998-2008) with the widespread introduction of herbicide-resistant crops, GHG emmissions decreased by an annual rate equivalent to 4.6 terragrams (Tg)  of CO2 per year. A terragram (Tg) is a unit equal to 1 million tonnes. The decrease era saw an increased adoption of no-till practices at the expense of both conventional till and conservation till (strip-till, ridge-till, min-till, and mulch till) practices in the Mississippi River basin, the Corn Belt, the lower Mississippi alluvial valley and small pockets on the East Coast. The net decrease in GHG during this year was equivalent to 61 Tg of CO2.

With the discovery of herbicide-resistant weeds tillage increased and GHG rose faster than they had declined, the equivalent of about 2.7 Tg of CO@ per year. The increase time frame (2008-2016) saw decreasing no-till in the South and lower Midwest and more intense tilling in the central and northern Midwest. During this period, the net increase of CO2 was equivalent to 110 Tg of CO2 per year, erasing the gains of the decrease period.

Illinois, Indiana, Nebraska, North Dakota and Minnesota all reported high swings in practices across the years. The researchers report that uncertainty about the most recent period (2016 to today) remains high, and point out that herbicide-resistant weeds, which appear to have driven farmers back to tilling during the increase period, remain an area of concern.

As weed resistance persists or grows, tillage intensity is anticipated to continue rising, probably increasing GHG emissions. The results imply that farmers’ choices in managing herbicide resistance may help mitigate agricultural GHG emissions, underscoring the importance of an alternative strategy to control weeds. A broader application of crop rotation, cover cropping, residue retention, and a more restricted and varied herbicide regime are all tools at hand to combat weeds while maintaining reduced tillage practices.