Sep 18, 2014
Plastic aids strawberry growth in Kansas

Kansas isn’t known as a strawberry-producing state, but some innovative growers, helped by a couple of strategic research grants, are figuring out the best way to adapt annual plasticulture methods in a state where production – historically done by the matted-row method – had all but died out except for a few small producers.

Jerry Wohletz, a grower in Lawrence, Kansas, started raising strawberries on plastic in 2009, after meeting some Missouri and Arkansas growers at a southern Missouri field day.

“I was looking for something new and different,” he said.

Annual plasticulture offered the possibility of larger berries, higher yields and easy picking for u-pick, and didn’t require using his limited water resources to keep plants alive during the hot summers.

Because winters in his area are harsher, however, Wohletz found it was more difficult to get a crop large enough to be profitable using the practices popular in Missouri and Arkansas. When Cary Rivard became fruit and vegetable specialist at Kansas State University in 2010 and asked growers if they had research needs, Wohletz spoke up. They applied for and received a SARE Producer Grant in 2011, to study the effects of various weights of row covers and the best timing to apply the row covers as winter protection for the berries.

Melanie and Frank Gieringer and their son, Brice Wiswell, of Gieringer Orchard in nearby Edgerton, Kansas, attended a field day that was part of the Wohletz SARE grant and decided to start growing plasticulture strawberries. Their farm already raised peaches and blackberries for direct-to-consumer sales (as well as row crops), and they were looking for a crop to start the season and bring people to the farm.

“I wanted to grow a high-value crop that I could set a premium price for and that would provide a good u-pick experience,” Brice said.

Wohletz helped him get started, and they share planting equipment and labor.

A second, larger grant to Rivard in 2013, through the National Strawberry Sustainability Initiative (NSSI), allowed them to continue the project, expand the research to university plots, add Gieringer Farm as a cooperator, explore tunnel production and develop Extension resources. The grants helped purchase thousands of dollars of temperature probes to collect microclimate data.

With only a few years of data – one of those the extremely harsh winter of 2014 – results are not clear-cut, but they are instructive. They now know that using row covers is essential (the minus 14˚ F temperatures in the winter of 2014 were a true test), and they are seeing a small benefit to using 1.2-ounce or 1.5-ounce covers rather than 1-ounce covers.

“Our biggest concern using covers was that if the covers were too heavy, the plants would come out of dormancy too early,” Wohletz said.

Their data loggers are revealing that heavier covers actually moderate the temperature in early spring, helping to avoid heat spikes. Heavier covers are also providing a slight increase in yields.

Wohletz said that an increase of .05 lb./plant doesn’t sound like a lot, but with more than 16,000 plants per acre that translates into a value of $1,500 per acre.

They’ve also learned that covering earlier is advisable – and that early cold snaps need to be taken seriously. Late last November, earlier than their research protocol called for applying covers, a quick cold snap swept through the area, bringing temperatures below 10˚ F. Because Brice Wiswell chose to cover all the rest of his plantings to avoid economic loss, it was easy to see the benefits of that decision.

“Our data from the previous winter showed that when we get below 10 degrees, we should have temperatures in the mid-20s underneath the row cover,” Rivard said. “So, when Brice called and asked about covering early, we were able to make an educated recommendation as to what the effects of the covers would be.”

They have also sought out expertise and experience in other regions, especially North Carolina, where growers and North Carolina State University researchers have decades of experience with strawberry plasticulture.

North Carolina research on planting date confirmed the crucial importance of finding the correct planting window. The Kansas growers have realized that they need to plant earlier than Missouri growers do, moving to a planting date of Sept. 7 rather than Sept. 15. Getting plug plants that early is a challenge, however, so they’ve had to develop new supplier relationships. Wiswell is confident that with good plants, row covers, proper timing and a reasonably “normal” winter, he can get close to the target – and profitable – yield of 1 pound per plant.

The high tunnel part of the research looks promising, Rivard said.

“We’ve been working with spring-planted, day-neutral varieties grown in the tunnel with shade cloth and evaporative cooling this summer as part of the NSSI project,” he said. “However, it is by no means clear that offseason local strawberries, even if productive and easily marketed, can survive the hot temperatures in the Great Plains. So far, our results have been very good, but it has also been an unusually mild summer in Kansas. We will try this system again next year before we start recommending it to growers.”

What has been especially impressive for both farms is the outpouring of consumer enthusiasm for their strawberries. They each have 2 to 3 acres of berries now, but could easily sell more, and customers don’t balk at u-pick prices of $2.50-$2.59 a pound and farmers’ market prices of $7 a quart.

“All our publicity has been through Facebook and social media,” Wiswell said. “People find out about us and spread the word.”

Debby Wechsler

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