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Incorporating cover crops into an annual crop rotation can be used to manage soil fertility, weed suppression, and erosion control. Additionally, cover crops with a flowering stage have the potential to support beneficial insect communities such as native and honey bees. Native and honey bees are considered important agricultural pollinators and both groups of bees share many of the same requirements to thrive.
While most of the world’s staple crops (corn, wheat, rice) are wind pollinated, it is estimated that one in every four mouthfuls of food and beverages consumed is dependent on pollinators.1 Insect-pollinated agricultural commodities account for over $29 billion in annual U.S. production.2 Since 2006, commercial beekeepers have noted challenges to honey bee populations due to a combination of stresses, including loss of natural forage and inadequate diets, mite infestations and disease, and pesticides. Growing flowering cover crops during fallow periods in the crop rotation is a multi-purpose strategy that may benefit crop productivity as well as the local pollinator community.
With appropriate plant selection and proper management, flowering cover crops can fulfill their original purpose as a conservation practice while at the same time providing valuable forage for bees.The plants that best fit a farm’s needs will vary by location and purpose. Different cover crops have different strengths (Table 1). Flowering broadleaf species are a must when selecting cover crops for pollinators. Grass cover crops do not provide nectar and their pollen typically has lower protein content than the pollen of broadleaf plants, making them only marginally attractive to bees. A flowering plant/grass blend may be a solution where a grass crop is needed to achieve other management priorities.
The cover crop species selected will depend on the timing of the crop crop in the cropping system. It is important to understand the limits of a window between main crops and if a cover crop is likely to flower before the next cash crop needs to be planted. One solution for a short cash crop window is to consider leaving some unmanaged cover crop strips in the field a few extra weeks. This will allow the cover crop to reach full flowering potential and can then be mowed or terminated by tillage or herbicide application before setting seed.
The chosen cover crop should be adapted to local conditions. Monocultures of flowering cover crops will be more attractive to bees at peak flower than a neighboring cover crop mixture. However, multi-species cover crop mixes are a simple way to provide maximum potential benefit for soil health, crop productivity, and pollinator conservation.