Being near pollinator habitat increases the size of soybeans

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Researchers at North Carolina State University have found that soybean crops planted near pollinator habitat produce larger soybean seeds than soybean crops that are not planted near pollinator habitat.

“Even though soybeans are not considered pollinator-dependent, we have found that soybean plants are still attractive to bees,” says Hannah Levenson, postdoctoral researcher at NC State and corresponding author of a paper on the work. . “And we found that the presence of pollinators was associated with larger soybeans.

“There’s been a lot of work on how planting pollinator habitats near crop fields can affect crops that are considered pollinator-dependent, like blueberries or strawberries,” Levenson says. “But there has been relatively little work on crops that are not considered pollinator-dependent. We wanted to know how pollinator habitat near soybean fields would affect both bee species and soybean crop yields.

The researchers chose to focus on soybeans because it is an economically important crop that is grown in dozens of states.

For the study, researchers worked at eight research stations across North Carolina. At each station, the researchers assessed two soybean fields: one that was adjacent to an established area of ​​pollinator habitat and one that was as far away as possible – usually within a kilometer.

Pollinator habitat was created by planting wildflower seed mixes in waste land near fields. Habitat could be cultivated in areas that are not suitable for growing crops or on land that can be used to grow crops but has not been cultivated this season due to crop rotation or other factors.

To assess the impact on the bees, the researchers did two things. First, they studied bee communities in soybean fields and pollinator habitat at each research station. The surveys consisted of a detailed visual assessment to establish the overall abundance of bees, as well as the species present at each location. The researchers also collected samples from individual bees to confirm their identifications.

The research team also collected pollen samples from three of the most common bee species, allowing them to determine which plants the bees were visiting.

“From the survey, we found that bee communities in pollinator habitats were completely distinct from bee communities in remote soybean fields,” says Levenson. “Bee communities in soybean fields adjacent to pollinator habitats were somewhat of a mix, including elements of the other two groups. The fields adjacent to the habitat were quite similar to the distant soybean fields, but had different bee communities that were clearly influenced by nearby pollinator habitat.

“From the pollen samples, we learned that all the bees we found in one of the soybean fields were actively visiting the soybean flowers,” says co-author and graduate student April Sharp. of NC State who worked on the project. as a first cycle. “Evidence suggests that some of the bees in the pollinator habitat itself were also visiting soybean flowers, although this is less pronounced.”

The researchers also found that bees in soybean fields located far from pollinator habitats often left the soybean fields to visit flowers completely outside the study area. Bees in soybean fields adjacent to pollinator habitat were less likely to leave the study area.

“This suggests that the presence of nearby pollinator habitat is beneficial for bees in soybean fields,” Levenson says.

To assess the impact on crop yields, the researchers collected 30 soybean plants from each of the fields at harvest time. They then counted the number of seeds – or soybeans – per pod, the total number of seeds per plant, and the weight of those seeds.

“We found that seed counts were similar for fields close to pollinator habitat and fields far away,” says Levenson. “However, plants in fields adjacent to pollinator habitat produced seeds that were 6.5% heavier than seeds from plants in distant fields.”

“It’s a substantial difference in the size of soybeans,” says David Tarpy, co-author of the paper and professor of applied ecology at NC State. “Since soybean growers sell their crop by weight, this could make a significant difference in a grower’s profit margin.”

“Our results are highly applicable to Southeast soybean growers,” Levenson says. “Other regions, such as the Midwest, have different cropping systems, so it’s unclear to what extent these results would apply there — this is an interesting area for future study. This work also raises questions about the role pollinators might play in affecting other crops that are not thought to be pollinator dependent, and this is another area worth exploring.

The article, “Evaluating the Impact of Increased Pollinator Habitat on Bee Visits and Yield Measures in Soybean Crops,” is published in the journal Agriculture, Ecosystems & Environment. The work was done with support from the North Carolina Department of Agriculture and Consumer Services, the Syngenta Pollinator and IPM Stewardship Program, and Southern SARE, under grant number GS19-215.

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Note to Editors: The summary of the study follows.

“Assessing the impact of increased pollinator habitat on bee attendance and yield metrics in soybean crops”

Authors: Hannah K. Levenson, April E. Sharp and David R. Tarpy, North Carolina State University

Published: February 17, Agriculture, Ecosystems & Environment

DO I: 10.1016/j.agee.2022.107901

Abstract: The intensification of agriculture has considerably modified the functioning of ecosystems and contributed to the reduction of global biodiversity. As agriculture requires an increased reliance on animal pollination, pollinator populations have declined. To combat this, the addition of pollinator habitats to agricultural landscapes is increasingly common, but many questions remain about its functionality and impact on agroecosystems, especially in pollinator-independent crops. Our study uses pollinator habitats planted on experimental research stations in the southeastern United States to assess their impact on pollinator communities within a nearby cropping system (soybean) and the resulting yield. results. We found that the species composition of pollinator communities within the habitat was significantly different from that of soybean communities. Even still, we identified more than 30 species of soybean flower-visiting bees and verified that a subset of these species actively collected soybean pollen. Bees from soybean fields planted adjacent to habitat had more habitat pollen types present, while some species had more non-habitat types present when in the negative control sites. The presence of habitat had a positive effect on some yield measures, with adjacent soybean sites having an average of 6.52% heavier seeds per plant. These results demonstrate that pollinator habitat can be an important resource to support pollinators and highlight the importance of considering pollinator habitat in pollinator-independent crops, as they can still benefit and be attractive to pollinator communities. .

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