Maintaining healthy soil is a crucial step in the production of strawberries. The chemical, physical, and biological properties of the soil, and how those characteristics are managed, all contribute to the health of the soil and its ability to support the production of berry crops.
Marvin Pritts, a professor at Cornell College of Agriculture and Life Sciences, offers growers tips to maintaining soil for optimum health.
Pritts began taking a closer look at strawberry soil health a couple of decades ago, after he and his colleagues had started wondering why strawberry performance varied so much from field to field among New York growers. They completed a study looking at many different measurable variables and correlating the findings to strawberry root health.
What they found was that the longer strawberry plants were kept in the field, the poorer root health would be, said Pritts. When plants are in the ground for three to four years, soil disease has time to accumulate.
One of the problems growers often run into is black root rot, which is “kind of a catch-all phrase for ‘my roots don’t look very good,’” Pritts said.
It’s often the result of pathogen build up in the soil. Poor root health can be associated with various factors, including:
- Growers not rotating crops
- Soil compaction
- Use of certain herbicides
That fumigation was associated with decline in soil health was a somewhat unexpected finding, said Pritts. When the study was done, it was more common for growers to use fumigation on their farms. Fumigation seemed to help strawberries in the first year or so, but after that, it would cause soil health to decline, Pritts said.
“What we hypothesized was that fumigation kills all of the microorganisms. In a few years, when there is nothing there to compete with the bad guys, they can really take over,” Pritts said.
While annual systems may be able to handle fumigation, in cooler regions where strawberries are typically grown as perennials, longer term fumigation can lead to problems. It gives harmful microorganisms the chance to build up to higher levels.
One area that remains somewhat unexplored is how herbicides impact soil health. According to Pritts, many herbicides were developed for corn and soybeans, but not necessarily minor crops. The herbicides that are labeled for berries tend to be older, and not well-studied in terms of impact on root health. There is, however, evidence that the herbicide Sinbar is harmful for root health, Pritts said.
A Holistic Approach to Soil Health Can Be More Effective
Many growers are accustomed to focusing on the chemical properties of the soil, and soil tests are a common method for determining soil’s nutrient needs. Traditionally, consultants look at the chemical properties of soil and use their findings to recommend a fertilizer.
“That’s how we thought about things for years,” Pritts says. “We’re moving from a mindset where the only thing people pay attention to is the nutrients in the soil, to a more holistic approach.”
This means addressing not only the chemical properties, but also the physical and biological properties of soil to get a more complete picture of its overall health.
Methods for Improving Soil Health
There are various ways growers can improve their soil health, and ultimately improve strawberry production. Two highly effective methods to improve soil are cover cropping between strawberry crops and composting, said Pritts. These actions put carbon into the soil, and result in a larger number of microorganisms in the soil, which then help suppress the harmful pathogens that try to establish in the soil.
Pritts’ research determined that certain combinations of cover crops work really well to help preserve soil health, including mustards, sweet corn, kale, rye, and some marigolds. Another benefit of cover cropping is that it improves the soil’s water holding capacity and drainage. Growers should work in cover crops right after the berry crop is taken out, and take about a year and a half to grow cover crops.
According to Pritts, composting seemed to improve performance of strawberries after they were planted. Compost can be applied anytime, though most growers do it in the spring, Pritts said.
Since some varieties are more resistant to pathogens than others, growers can improve their soil situation by breeding for resistance as well.
For more guidance on improving soil health, Pritts directs growers to two resources provided by Cornell for commercial berry growers — this includes a manual on berry soil and nutrient management, as well as a series of webinars on the same topics.