Integrating Cover Crops for Agroecosystem Services

Introduction

Cover crops are used in US agriculture¹ to improve soil conditions for a subsequent cash crop as an alternative to synthetic amendments.² Cover crops are primarily planted between cash crop growing seasons. Still, they can also be planted alongside cash crops as well as part of a polyculture system.

Producers and farmers have been slow to adopt cover crops as part of their crop rotation because of many factors, including a lack of regionally-appropriate information on cover crop selection, planting, maintenance, termination methods, and economics.^3,4,5 Despite this, interest in using cover crops is increasing, especially in the Southeast.³ Beyond the benefits for soil health, cover crops may also improve habitat for wildlife and beneficial arthropods within the agroecosystem.

Agroecosystem Services

There are many reasons why a producer may want to integrate cover crops into their agroecosystem. Farmers use cover crops to increase the availability of carbon,⁶ nitrogen,⁷ and other nutrients^8,9,10 in the soil by offering a favorable environment for microorganisms to live and by releasing or recycling them¹¹ for subsequent cash crops. Cover crops protect the soil from erosion by blocking wind,¹² reducing raindrop impact,^13,14 and holding the soil in place with their roots.¹⁵ Cover crops can help mitigate weather extremes¹⁶ by preserving soil moisture during drought,¹⁷ allowing for increased drainage via old root pores,¹⁸ or a combination thereof. Various cover crops break disease cycles¹⁹ and outcompete^20,21 or inhibit weeds and some arthropod pests.^{22, 23, 24} Cover crop selection is dependent on which service is preferred by farmers (e.g., weed suppression, nutrient addition, erosion control, or tilth improvement). The Southern Cover Crop Council’s Cover Crop Resource Guide (https://southerncovercrops.org/cover-crop-resource-guide/) can identify cover crops for a specific use. On the website, select your cropping system and the location of the farm, and then select the “Cover Crop Functions & Rankings” for the season (summer or winter) in which the cover is desired.

Provision of Food and Shelter for Songbirds and Arthropods

With habitat loss occurring every year, many wildlife species use farmland to fulfill basic requirements like food and shelter.²⁵ For example, leaving intact borders of natural vegetation or planted crops (cover or cash) around fields does not negatively affect yield and attracts wildlife for shelter and food.²⁶ Songbirds, particularly grassland songbirds, may be attracted to cover crops because of increased habitat and food resources,²⁷ especially in the breeding season when insects become the main part of their diet.²⁸ Nesting success of insectivorous birds of conservation concern such as the loggerhead shrike,^28,29 may increase due to greater habitat variety that cover crops provide, which also increases their food choices.²⁹

Secondary Agroecosystem Services

Using cover crops to provide habitat to arthropod and wildlife can result in both ecosystem services and disservices. Pollination of and pest control within cash crops can increase due to cover crops.²⁶ For example, sunflowers (Helianthus spp.) can attract predatory arthropods once they reach six inches in height,³⁰ as well as pollinators and parasitoids once they begin to flower.³⁰ The type of cover crop planted can influence the community of pollinators that forage in that area.³¹ For example, a radish (Raphanus sativus) cover crop reduces soil compaction and attracts parasitoids, while a sunn hemp (Crotalaria juncea) cover crop fixes nitrogen and attracts wild bees.³² Pollinators, especially bees, are a considerable benefit to agriculture, as they account for 35% of crop production worldwide.^33,34 When used as a floral border for cabbage, buckwheat (Fagopyrum esculentum) provides nectar as a food source for parasitic wasps that can help control pest caterpillars.³⁵ Along with bees, butterflies, and flies, parasitoid insects also act as pollinators.³⁶ Carabid beetles have a varied diet and can consume arthropod pests as well as weed seeds³⁷ and are attracted to many cover crops, which provide the beetles with an abundance of food and favorable microclimate conditions.³² Some cover crops are planted as a “decoy” crop, meaning that they are planted to attract wildlife away from the cash crop by offering better shelter or food. For example, planting specific varieties of sunflowers reduces seed predation by blackbirds on other sunflower varieties that were being grown as a cash crop.³⁸

Some birds and arthropods that are attracted to the cover crops may be considered pests themselves. Generalist pests can find refuge in cover crops if there is no suitable host plant or if the host plant cannot provide resources.³⁹ Cover crops may offer other wildlife shelter and a food source when they otherwise would leave the area in search for these services elsewhere. In both cases, the cover crop provides an opportunity for these pests to stay and damage the next cash crops.⁴⁰

Provision of Food for Larger Animals Including Game

Landowners often use cover crops to create food plots and increase hunting opportunities for game species such as white-tailed deer,⁴¹ wild turkey,⁴² mourning dove,⁴³ and northern bobwhite.⁴⁴ However, deer and turkey can become pests in agricultural production systems, as well as feral hogs, an invasive species that has a severe impact on agriculture and the environment.^45,46 Cover crop food plots also attract incidental species such as songbirds, cottontail rabbits, raccoons, and rodents.⁴⁷ While the latter are considered pests in agricultural production systems due to food safety issues and direct crop consumption, some species of raptors, like the American kestrel, are potentially providing pest control of rodents.⁴⁸

Summary

Cover crops not only benefit soil health by cycling nutrients, preventing erosion, safeguarding against weather extremes, reducing compaction, and suppressing weeds, but they also offer wildlife services. Farmers, producers, and forestry managers can identify which cover crops will support specific wildlife services in the southeastern United States. Consult table 1 to identify which cover crops support desired arthropod(s) and other wildlife.^{37,38,40,41,46}

Table 1. Arthropods and other wildlife supported by commonly utilized cover crops in the southeastern United States.

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