(Radio Iowa) – Iowa State University researchers say an earlier planting date for soybeans in the spring takes better advantage of nitrogen left behind from corn production. I-S-U agronomy professor Michael Castellano says it would help reduce nitrous oxide emissions.
“Forty percent of the emissions from a two-year sequence — or rotation we might call it — of corn and soybeans comes during the soybean part of the crop rotation that doesn’t receive nitrogen fertilizer,” Castellano says. “…This was a big surprise and really required rethinking of approaches to reduce nitrous oxide emissions from crop production.” Crop rotation – planting corn in a field one year and soybeans the following year — already reduces emissions by 50 percent.
Castellano says most research has focused on reducing the amount of nitrogen applied to help corn grow, which also reduces farm chemical costs. Castellano says this new research finds that once nitrogen for corn production is reduced to the optimum level, the main way to cut nitrous oxide emissions is to move up the planting date of soybeans.
“It takes better advantage of the nitrogen being produced by the microbes in the soil, so the plants use it and less of it is lost to the atmosphere as nitrous oxide,” Castellano says. “Simple, practical, scalable solutions to help reduce nitrous oxide emissions from crop production that we may not often hear about.” Nitrous oxide is the primary source of greenhouse gas emissions from crop production. Nitrous oxide is the byproduct of microbial activity in soil that is essential for growing grain.
Castellano says farmers tend to focus on getting corn in the ground early because it’s a more expensive crop to grow, but moving up the soybean planting date is likely to result in higher soybean yields because the plants have a longer growing season. “Springs are getting warmer in Iowa and another real challenge, though, is that the spring are getting wetter, too,” Castellano says, “and so it’s going to require farmers to think about opportunities to manage their soil and their cropping systems.” Castello and another I-S-U researcher worked on this project, which dramatically increased the amount of time plants are growing on farmland.
Cover crops were planted after the beans were harvested. “And also got reductions in nitrous oxide as well as nitrate leaching,” he says, “so water quality benefits as well.”
The study was published in the November issue of a scientific journal called “Nature Sustainability.”
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