Imagine buying a dozen eggs at a grocery store, but when you get home and open the carton, there’s only a half dozen inside because you weren’t buying a dozen eggs. You were buying approximately 12 eggs, plus or minus six.
That’s how Andrew VanLoocke often describes a project he has led to develop a more reliable way to estimate how tillage, the methods farmers use to prepare their farmland for planting crops, affects soil carbon levels and yield. The accuracy of those estimates is important to farmers, as yield is always a baseline concern and sufficient levels of organic carbon make soil more productive and stable.
Tillage’s impact on soil carbon is also important to companies that pay farmers to reduce tilling to help meet corporate carbon emissions goals.
“These companies want the best, most transparent estimates possible to ensure they're getting a dozen eggs instead of six,” said VanLoocke, an associate professor of agronomy at Iowa State University.
A database built by Iowa State researchers aims to provide more certainty by digging deep into the effects of tillage, integrating the results of more than 250 peer-reviewed studies.
“We’ve taken a lot of useful science already done by many different people in many different places and put it together in a way that can be even more useful,” VanLoocke said.
Going granular
The project began about five years ago when Zach Simpson – at the time a post-doctoral research associate for Marshall McDaniel, an associate professor of agronomy at Iowa State – began collecting data to analyze how tillage affects multiple aspects of cropping systems.
“I think he was just tired of everyone coming up with different answers,” VanLoocke said of Simpson, now a researcher at Aarhus University in Denmark.
Studies included in the database were identified by reviewing two meta-analysis papers that collected global research into how tillage affects soil organic carbon and crop yield. Including yield in the analysis was important because while no-till farming typically increases soil carbon, it also tends to reduce yield, McDaniel said. The balance between no-till’s benefits and tradeoffs needs to be better understood, he said.
“One of the goals in science, especially in environmental science, is to inform decision-making. So, we have to understand the consequences for yield,” he said.
Limiting their analysis to research based in North America, the Iowa State team extracted detailed information often missed in the average effects estimated by meta-analysis studies – soil conditions, climate and the presence of irrigation, for instance. Tillage was classified on a continuum of intensity instead of an either-or basis, five stages ranging from deep soil-turning to completely hands-off no-till.
Source : iastate.edu