Tips To Step Up Your Strawberry Nutrient Management Plan

There are a lot of variables that go into developing a well-rounded nutrient plan for strawberries, which include soil testing, tissue testing, fertilizer timing, and much more.
Marvin Pritts, professor of plant science at Cornell University, shares tips to guide you through each step of the process, explaining how to tell what nutrients your crop may be deficient in, and providing the necessary tools to help balance your soil and ensure a healthy stand.

Marvin Pritts

Marvin Pritts

Basic Deficiency Symptoms
When mobile nutrients such as nitrogen or potassium are present, you’ll typically see deficiency symptoms in the older leaves first because they move to areas of the plant where demand is the highest, Pritts says.

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“One of the first things you’ll see is that the older leaves are yellow or burnt at the margin, and the younger leaves are healthy,” he explains.
Conversely, if you see symptoms developing in the younger leaves, it’s likely the nutrients are not mobile, giving you a second set of deficiencies you have to narrow down.

“Depending on the nutrient, you’ll see a loss of chlorophyll, and that would happen with low nitrogen, or low iron, which will give you a yellowing of the leaves. Other deficiencies like potassium will give you a burning of the leaf margin.”

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Pritts notes boron tends to be deficient in many soils as well, and deficiencies will manifest in fruit as shrunken berries, asymmetrical growth, and poor root development. Furthermore, if there are low levels of boron, Pritts says deficiencies in other nutrients may present themselves. .

“If you correct the boron, the other deficiencies tend to correct themselves over time. Nutrients that might be deficient in this case would be phosphorous and potassium,” Pritts explains.

Application Timing
According to Pritts, nutrients can typically be applied to strawberry plants any time of year, except for nitrogen.

“If you put nitrogen on in the springtime, it’s usually a bit too much. This can cause the fruit to get soft, the leaves to become very vegetative and create a dense canopy,” Pritts explains.

For this reason he suggests waiting until after harvest, or when the fruit is on in late July or early August. For other nutrients, fall is typically the best application time because that way they have time to work themselves into the soil and root zone before springtime arrives.

Soil Testing And Tissue Analysis
Conducting regular soil and foliar tests is crucial when determining what nutrients are lacking and need to be reincorporated into your management plan.

The most important time to conduct a soil test, Pritts says, is right before planting so you can correct any issues in advance.

“In most cases strawberries tend to be a short-lived crop. If the grower does a good job with soil testing and makes those corrections they may never have to soil test again for the life of that planting,” he explains.

So what should you be looking for in your soil test? Pritts says the first thing to take note of is the pH, because if the pH is off the plants won’t be able to take up the available nutrients. For strawberries he says the ideal pH is between 5.8 and 6.5.

Regarding nutrients, the big four to look for are phosphorous, potassium, magnesium, and calcium, and he says to evaluate levels to make sure they’re adequate for the next several years.

Tissue analysis, on the other hand, should be done after the first harvest is over in July, because it’s at that time in the season the values in the leaves are the most consistent.

“If you sample leaves early when the plants are fruiting, lots of things are happening with the plants. The nutrients are moving around from the roots to the fruit — you won’t get a very stable reading,” he explains.Applying Fertilizer
As for what types of fertilizer to apply to the plants, when it comes to nitrogen Pritts says strawberries do not have a strong preference for where it comes from.

“Strawberries are good at taking up any source of nitrogen, and as long as the pH is correct and the microorganisms in the soil can convert the ammonium forms of nitrogen into the nitrate forms, the plants can take it up and use it,” he says.

He does caution if the pH in the soil is already low, ammonium sources of fertilizers tend to push the pH even lower, so in this case he suggests using a nitrate source of nitrogen instead.

For potassium application, he does not recommend the use of potassium chloride or potash because too much chloride can be toxic to plants, and suggests potassium sulfate or magnesium sulfate as alternatives.

For organic production, he explains many natural sources of phosphorous are slow to release, so you may have to apply a little more than you would normally because they don’t break down as quickly as synthetic forms.

Creating Biologically Active Soil
Providing nutrients through organic sources like manure and compost not only provides the nutrients your strawberries need, but also provides carbon which then feeds the microorganisms in the soil, and it gives you better biological activity and overall soil health, says Pritts.

“Cover crops, manure, and compost are all good sources of carbon. Strawberry growers also place straw over the strawberries in the wintertime and that’s a good source of carbon as well,” he explains.

He does caution against too much compost, and says if you’re growing in heavier soils which tend to hold more water, adding too much compost can turn soil into a “sponge,” which may attract pathogens.

For this reason, proper drainage is a must, regardless of what soil type you’re working with.

“Anything you can do to prevent standing water, you’re going to have much healthier plants. You can do that by putting drain tiles in the field, and that carries off water when it gets high, or you can plant on raised beds,” he suggests.

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