The role of cover crops as a floral resource for native bee conservation in agroecosystems

2012 Annual Report for GNE12-037

Project Type: Graduate Student
Funds awarded in 2012: $14,929.00
Projected End Date: 12/31/2014
Grant Recipient: Penn State University
Region: Northeast
State: Pennsylvania
Graduate Student:
Faculty Advisor:
Mary Barbercheck
PSU Dept. of Entomology

The role of cover crops as a floral resource for native bee conservation in agroecosystems


Conservation of natural processes such as pollination, pest control, and nutrient cycling are essential to maintaining a healthy agroecosystem. The incorporation of cover crops into annual crop rotations is one practice that is used in the Northeast U.S. to manage soil fertility, weed suppression, and erosion control. Additionally, cover crops that have a flowering stage have the potential to support beneficial insect communities, such as native bees. Because of the current decline facing managed honeybee colonies, the conservation of native bee communities is critical to maintaining ‘free’ pollination services. However, native bees are negatively affected by agricultural intensification and are in decline across North America. This project will assess the potential of flowering cover crop species to act as a conservation resource for native bee communities, in addition to providing benefits to soil fertility and agricultural production.

Three flowering cover crop species will be evaluated to determine their various blooming time frames as well as the different native bee communities that use their resources. Each cover crop has been planted in four planting dates spanning from early August until early October. This planting date gradient will help to evaluate their potential use and spring blooming time differences in many standard crop rotations in the Northeastern US. Project results will be distributed to the public, particularly farmers and land managers, through a series of extension publications and field days highlighting the role of cover crops in native pollinator conservation. The effectiveness of these publications in changing knowledge and intention for behavior change will be evaluated.

Objectives/Performance Targets

OBJECTIVE 1: To identify (a) the blooming time frames of three common Northeast U.S. flowering cover crop plant species, and (b) the effect of cover crop planting and termination date on peak bloom.

Objective 1 accomplishments to date:
The original proposal was designed to study six cover crop species over two fall planting dates. After contemplation this was altered to three cover crop species and four planting dates so as to better represent a fall planting gradient and allow for a more robust model for how these planting dates would fit into a variety of Northeast cash crop rotations. This also allowed for a greater variety of fall climate effects on each planting date to be observed.
At this point in time, each crop and planting date was successfully established within the desired timeframe. The effect of planting date on crop bloom is still to be determined.

OBJECTIVE 2: To identify (a) the native bee species that visit cover crop flowers for pollen and nectar resources, (b) when those bee species are most abundant in the environment and how that relates to cover crop bloom, and (c) what potential pollinator benefits may be lost through early termination of cover crops in standard crop rotations.

Objective 2 accomplishments to date:
This objective will be completed in the spring when each cover crop begins to bloom and the bees emerge from their overwintering habitats. No cover crop reached bloom in the fall, regardless of the differences in fall growth between August and October planting dates.

OBJECTIVE 3: (a) To participate in a series of public outreach activities highlighting the benefits of flowering cover crops for conservation of native bee species. (b) To create and distribute an extension publication that illustrates the results of this project and assists growers in determining the optimal species for use in their rotation.

Objective 3 accomplishments to date:
This objective will be completed at the earliest next summer when some of the spring data results have been collected and analyzed.


So far this season the project has progressed mostly as planned and hoped. A few changes were instituted before anything was planted, most notably the alteration of the actual cover crops being studied from the proposed six species to a select group of three. This allowed for more planting dates to be considered on the same area of land and the same number of plots as in the original plan. Additionally, the actual shape and locations of the plots had to be altered when we went and tried to plant the first crop. The planting tool that was ultimately used was a 9 row (6 foot) tractor-pulled drill. While this helped to standardize planting depth and size between plots, it also necessitated a need for long and linear plots that were stacked by planting date. Consequently the overall plot layout was altered so that each block (which there are still four block replications) contained three large plots and four subplots. The larger plots were grouped by crop and each subplot is a planting date. All plots and subplot strips were randomly assigned.

The first planting date was set to represent an early winter wheat harvest date, late July to early August, and each subsequent planting date was set for three weeks after. For the most part this three-week spacing was quite accurate with only a difference of one or two days to accommodate weather and planter availability.

Additionally, daily high and low temperatures and precipitation were recorded for each planting date. This information will be used to calculate the differences in growing degree days between each of the planting dates and will be considered along with the data from a fall biomass sampling as a covariate for differences in fall plant growth as it may affect spring bloom.

I, personally, learned a great deal about the logistics of agronomic planting, planning, and ground maintenance. Acquiring, prepping and planting seeds, riding on the back of the tractor drill during the planting process, and working the ground to limit weed growth were all great hands-on learning opportunities for me this summer and fall.

Impacts and Contributions/Outcomes

As this is still an ongoing project there are no current results regarding the potential use of flowering cover crops as a bee conservation resource. It is my hope that I can use the future results of this project to not only promote the use of flowering cover crops as a beneficial farming practice, but to also increase public awareness of native bees and the different types of conservation methods that Northeastern farmers can adopt with limited additional costs. These results will likely be distributed to local growers and land managers via extension publications and as part of public field days that happen at the University research farm each summer.


Dr. Mary Barbercheck

[email protected]
Professor of Entomology
Penn State University
501 ASI Building
University Park, PA 16802
Office Phone: 8148632982