Feb 6, 2025

Cover crops for berry growers

As berry growers increasingly seek sustainable practices to enhance soil health, the use of cover crops is emerging as a powerful tool that offers both benefits and challenges in cultivating vibrant yields.

We know roots of cover crops and their exudates provide organic matter to the soil, which builds soil carbon and can promote soil health. This is especially important in cover crops for berry growers, where the shoot biomass is also incorporated through tillage and or in low-to-no till conditions.

Cheyenne Sloan, a soil scientist and blueberry and small fruit educator for Michigan State University (MSU) Extension, noted within annual cropping systems like blueberries or raspberries, growers will have crops within their rows anyway, so it’s important they pick something that will help their soil do what they want to do.

“By being deliberate about the type of cover crops you pick, you can help improve soil organic matter. The more soil organic matter you have, the more water your soil can hold, the more food there is for microbes that live in the soil and are what really power the nutrient cycle,” she said. By incorporating soil organic matter, not only is the soil organic amount high, but the solid possesses lots of space to hold nutrients.

Additionally, cover crops can help prevent soil runoff and absorb more water if there’s an excess of rain throughout the berry growing season.

Chris Benedict, regional Extension specialist for Washington State University, notes some cover crops, like legumes that fix nitrogen, can increase soil nitrogen content. In addition, root growth and exudates promote soil biological activity and can help with aggregation of soil particles, which can in turn promote improved soil structure.

“Cover crops may also benefit management of certain soilborne diseases and pests,” he said. “For example, some cover crops in the mustard family produce sulfur-containing chemical compounds called isothiocyanates. These isothiocyanates can stimulate a soil microbial community and environment suppressive to certain soilborne pathogens and plant-parasitic nematodes.”

Other cover crops in alleyways or adjacent to crop fields may also provide a refuge for pollinators and arthropods that can act as predators or parasites of pest species, but care must be taken to not harm these beneficials through routine spray applications that may generate drift.

Enhancing berry protection

Lisa W. DeVetter, associate professor of small fruit horticulture at Washington State University, notes the specific type of cover crop for berry growers depends on the type of berry system and goals of the producer.

“In some cases, a cover crop established in between plantings can protect the ground from erosion, add carbon and nutrients and suppress weeds prior to re-planting the next crop,” she said. “Annual cover crops such as cereal grasses, planted in between berry rows during winter, can help alleviate compaction and reduce water ponding, potentially allowing for earlier access to the field in spring. Perennial alleyway cover crops of grass or other species can keep dust down, prevent water ponding and also add carbon to the soil.”

Sloan said not a lot of research has been done on specific cover crops that work best with berries, and that’s an MSU Extension goal.

“From my research, I wasn’t able to find any good, solid recommendations for berries yet, and that’s definitely something that we need to find,” she said. “However, if someone asked me what to plant, I would recommend some kind of grass, because they create the most biomass and have different types of root structures and so are able to help build the soil, create biomass and improve soil health.”

For those who want to put in nitrogen, she suggests using clover; if growers are worried about compaction, she recommends radishes.

Cover crop challenges

One of the drawbacks with cover crops, Sloan said, is the potential harboring of pests.

“I fight with several old-school blueberry growers here in Michigan because they just want to rototill in between all of their bushes because they are really worried about viruses and the movement of viruses in their soil,” she said. “So, if you’re really worried about viruses, cover crops may not be the best idea.”

Employing more of a crop mix or being more deliberate about the type of crops chosen can help improve soil health as well as fight and outcompete some of the bad plant parasitic microbes that live in the soil, Sloan said.

“Plus, by having more things there, it can dilute the effects, so maybe instead of (pests) going and munching on your blueberries and raspberries, they will stay in the row middles and not affect them as much,” Sloan said.

Like any new practice, there is a learning curve with cover crops, as some species may not establish as well and adjustments may be needed to determine the optimal cover crop and planting conditions. Additionally, variations in planting rates and mixes may work better on certain farms or fields.

“Some berry systems may want to consider humidity in the canopy if planting a summer or perennial cover crop,” Benedict said. “Planting cover crops takes additional time and inputs, and the benefits of cover crops may take time to realize, so a grower should consider it an investment in maintaining the health of their soil.”

He added that berry growers should get recommendations from area extension experts, as selecting the right cover crop will depend on local conditions and production goals.

Ultimately, the thoughtful implementation of cover crops can not only improve soil structure and health for berry growers but also foster a resilient agricultural ecosystem, making it essential for producers to carefully weigh their options and consult local experts to tailor their approach for optimal results.

— A graduate of the University of Miami, Keith Loria is an award-winning journalist who has been writing for almost 20 years. View his recent writing at keithloria.contently.com.