Why Cover Crops?

Cover crops are plants grown primarily to benefit the soil rather than for harvest. Their roots help improve soil structure, reduce erosion, increase organic matter, and support soil microbes. Many cover crops also compete with weeds, reducing the space and sunlight available for unwanted plants. The Nassau County demonstration garden has featured a diverse mixture of cover crops, including cowpea, Austrian winter pea, crimson clover, cereal rye, sunn hemp, chicory, oats, black oil sunflower, and browntop millet. These species were selected because of their ability to produce biomass, improve soil conditions, and provide habitat for beneficial organisms.

Building Soil with Compost

The 2,000-square-foot demonstration garden has received more than 1,000 pounds of compost made from yard waste, food scraps, and manure since 2022. The combination of compost, cover crop residues, and organic mulch has helped create a well-aerated sandy soil with improved biological activity. As organic materials break down, soil microorganisms convert nutrients into forms plants can use. This process supports long-term fertility while improving water-holding capacity and overall soil function.

Managing Weeds Naturally

One of the most noticeable benefits observed in the garden has been the suppression of several troublesome weeds. Reductions were observed in torpedograss, spreading dayflower, dollarweed, goosegrass, and root-knot nematodes over the course of the project. Weed management has relied on multiple strategies, including dense cover crop growth to shade the soil, organic mulches such as pine bark and oak leaves, removal of persistent weeds, and continuous addition of organic matter. Some weeds remain challenging, particularly bermudagrass, spreading dayflower, dollarweed, and goosegrass, but the integrated approach has reduced their impact while minimizing reliance on herbicides. Cultural controls, like laying down grain cover crops (oats, ryegrass, cereal rye, etc.) was also effective at controlling weeds and building soil residue.

Pollinators and Beneficial Insects Welcome

Healthy gardens are about more than just plants. Pollinators and beneficial insects play critical roles in pollination and natural pest control. The demonstration garden includes nearby nectar and pollen resources such as goldenrod, lyreleaf sage, Spanish needles (Bidens alba), red maple, muscadine grape, bottlebrush, and chicory. These plants help provide food and habitat throughout the year.

Biodiversity Benefits: What Wildlife Is Using the Garden?

One of the goals of the demonstration garden was to increase biological diversity while maintaining a productive growing space. To document wildlife use, observations were submitted to iNaturalist and reviewed by the platform’s community. Research-grade observations provide a useful indicator of which species are regularly utilizing the habitat. The most commonly documented reptiles and amphibians included brown anole (Anolis sagrei) – 15 observations, green anole (Anolis carolinensis) – 5 observations, eastern glass lizard (Ophisaurus ventralis) – 1 observatio, and a squirrel treefrog (Hyla squirella) – 1 observation. The presence of both native and nonnative reptiles demonstrates the value of dense vegetation, mulch layers, and ground cover as refuge habitat.

Insects and Other Arthropods

The garden supported a remarkably diverse arthropod community. The most commonly observed species included:

Predatory arthropods were also common and included yellow garden spiders, green lynx spiders, wolf spiders, crab spiders, robber flies, assassin bugs, and numerous predatory wasps. These species help regulate pest populations and contribute to natural biological control within the garden ecosystem.

A Living Demonstration of Ecological Function

The diversity of reptiles, birds, pollinators, predators, decomposers, and other organisms observed in the garden illustrates how cover crops, compost, mulch, and flowering plants can support a thriving food web. While the project was designed primarily to improve soil health and demonstrate sustainable gardening practices, it also became a small-scale refuge for dozens of species. Herbivorous insects such as caterpillars and grasshoppers play an important role in this system. For example, long-tailed skipper (Urbanus proteus) larvae feed on cowpea leaves and, in turn, provide food for predators observed in the garden, including milkweed assassin bugs, paper wasps, and spiders.

More Than a Soil-Building Project

Beyond improving soil health, the garden has been productive. Since establishment, it has produced vegetables, fruit, forage, vermicomposting feedstocks, and other useful crops including watermelon, collards, radish, kale, cowpeas, rosemary, butternut squash, and bottle gourds. Bottle gourds alone have produced an estimated 50 to 60 pounds of harvested material. They are used for birdhouses for our local 4-H Forest Ecology Club.

Cover crops have also generated substantial biomass. Since 2022, hundreds of pounds of fresh cowpea and Austrian winter pea biomass have been harvested from the demonstration garden. This material can be incorporated directly into the soil, used as mulch, or added to composting systems to recycle nutrients and build soil organic matter.

Because large amounts of nutrient-rich organic materials were added to the site, pine wood chips were applied as a carbon source to help balance decomposition processes. The resulting combination of compost, cover crop residues, and wood chips improved soil aggregation and contributed to the development of a healthier topsoil layer.

Evaluating Forage Quality

In addition to improving soil health and suppressing weeds, several cover crops grown in the demonstration garden were evaluated for their potential value as livestock forage. Laboratory analysis was used to assess crude protein (CP) and total digestible nutrients (TDN), two common measures of forage quality. Results showed excellent nutritional value among several species:

• Austrian winter pea: 34.2% crude protein (CP) and 90% total digestible nutrients (TDN)
• Alyce clover: 19.6% CP and 67% TDN
• Cowpea: 19.5% CP and 78% TDN
• Sunn hemp: 16.2% CP and 67% TDN

These results demonstrate that cover crops can provide multiple benefits beyond soil improvement. Species such as cowpea, alyce clover, Austrian winter pea, and sunn hemp can contribute organic matter for soil building while also producing high-quality forage for livestock. In integrated crop-livestock systems, these plants may help producers reduce feed costs, improve nutrient cycling, and increase the overall productivity of agricultural land. The forage quality data also highlight the versatility of cover crops. While many gardeners and farmers plant cover crops primarily for erosion control, weed suppression, nitrogen fixation, and pollinator support, these same species can generate valuable biomass that serves as livestock feed, compost feedstock, mulch, or soil amendments. The ability to obtain multiple benefits from a single planting is one reason cover crops remain an important component of sustainable agricultural systems.

Adapting to Local Soil Conditions

A soil test showed the demonstration garden has a pH between 7.5 and 8.0, which is higher than ideal for many vegetable crops. Rather than making drastic soil modifications, the project emphasized growing crops that tolerate alkaline conditions, including rosemary, chicory, cowpea, and bottle gourd.

This approach highlights an important gardening principle: understanding your soil and selecting suitable crops can often be just as effective as modifying site conditions.

Take-Home Message

The Nassau County demonstration garden illustrates how cover crops, compost, mulch, and pollinator habitat can work together to build healthier soils, reduce weed pressure, support beneficial insects, and produce useful harvests. These practices can be adapted at many scales, from backyard gardens to larger agricultural operations. Whether your goal is growing vegetables, improving soil quality, attracting pollinators, or reducing weed problems, investing in soil health today can provide benefits for years to come.

For more information about cover crops, composting, pollinator-friendly landscapes, and sustainable gardening practices, contact UF/IFAS Extension Nassau County.