North Carolina State University researchers discovered that soybean crops planted near pollinator habitat produce larger soybeans than soybean crops not planted near pollinator habitat. The researchers chose to focus on soybeans because they are a valuable crop grown in a number of states.
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"Even though soybeans are not thought to be pollinator-dependent, we discovered that soybean plants are still appealing to bees," says Hannah Levenson, a postdoctoral research scholar at NC State and corresponding author of a paper on the work. "We also discovered that the presence of pollinators was related to larger soybeans."
"A lot of research has been done on how planting pollinator habitat near crop fields can affect crops that are pollinator-dependent, such as blueberries or strawberries," Levenson says. "However, there has been little research on crops that are not pollinator-dependent. We wanted to know how having pollinator habitat near soybean fields affected both bee species and soybean crop yields."
The study was carried out at eight research stations spread across North Carolina. The researchers evaluated two soybean fields at each station: one adjacent to an established area of pollinator habitat and one as far away as possible – generally just under a kilometre away.
Planting wildflower seed mixes in unused land near fields created the pollinator habitat. The habitat could be grown in areas that aren't suitable for crop cultivation, or on land that is suitable for crop cultivation but hasn't been cultivated that season due to crop rotation or other factors.
The researchers did two things to assess the impact on bees. They began by surveying bee communities in both soybean fields and pollinator habitats at each research station. The surveys included a detailed visual assessment to determine overall bee abundance as well as which species were present at each location. Individual bee samples were also collected by the researchers in order to confirm their identifications.
The researchers also collected pollen samples from three of the most common bee species, which allowed them to determine which plants the bees visited.
"Based on the survey results, we discovered that the bee communities in pollinator habitats were completely distinct from the bee communities in distant soybean fields," Levenson says. "The bee communities in the soybean fields adjacent to pollinator habitats were a bit of a mix, with elements from both groups." The bee communities in the habitat-adjacent fields were similar to those in the distant soybean fields, but they were clearly influenced by the nearby pollinator habitat."
"We learned from the pollen samples that all of the bees we found in any of the soybean fields were actively visiting soybean flowers," says April Sharp, co-author of the paper and an NC State graduate student who worked on the project as an undergraduate. "The evidence indicates that some of the bees in the pollinator habitat itself were also visiting the soybean flowers, though that was less pronounced."
The researchers also discovered that bees in soybean fields far from pollinator habitats frequently left the fields to visit flowers completely outside of the study area. Bees in soybean fields near the pollinator habitat were less likely to leave the study area. "This suggests that bees in soybean fields benefit from having pollinator habitat nearby," Levenson says.
(Source: North Carolina State University)
