Midwest Strawberry Production Adapts to Plastic and Drip Tape System

Matted-row production of strawberries can move over in Kansas; the California strawberry production system that uses black plastic and drip irrigation is being successfully adapted for the Great Plains. So far, the system is working there just as well with or without methyl bromide.

Kansas State University Horticultural and Food Crops Research and Extension Specialist Alan Erb has been experimenting with the system for 3 years after seeing it successfully adapted in New Jersey and North Carolina. "We are finding that we are getting healthier plants, less disease, and keeping yield at the same level," Erb said.

In the traditional matted-row method for growing strawberries in Kansas, dormant crowns are planted in March, with 18 inches between plants and 48 inches between rows. In contrast, a system that has become the standard in California calls for soil to be mounded into rows and covered in black plastic, with a line of drip irrigation tubing between double rows. Plants are transplanted in early September in double rows 12 or 14 inches apart with 12 inches between plants. A floating row cover is added in early October and the strawberry plants are allowed to grow until late November.

When the row cover is removed, the plants go into winter dormancy. In early December, as with the matted-row system, they are covered with a thick layer of straw mulch and the row cover is reapplied. In March, the row cover and the mulch are removed, and the spring growing season begins.

The plastic and drip irrigation system does cost more than the matted-row method, due to the need for investing in specialized equipment and increased labor involved. But Erb points out that equipment costs are amortized over a number of years.

"And this system also allows plants to be harvested for 2 to 3 years before production begins to drop off rather than replacing them each year as is the current practice. This lets you recover some of the increased costs," he said.

To keep the plants producing for several years, they are cut back to the crowns right after harvesting ends in June. Not having to plug new plants each year offsets some of the increased labor required to put in this system, Erb pointed out.

Keeping the plants in production this way usually causes yield to increase but fruit size to drop. However, the reduction in size does not seem to be large enough to warrant re-establishing the beds every year.

The System Without Methyl Bromide

When Erb began working on adapting the plastic and drip irrigation method, he was not specifically considering it as a way of maintaining production without the use of methyl bromide. But given the impending ban, he felt it would be valuable to set up test plots both with and without methyl bromide as a soil fumigant before planting.

To get a basic reading on the system's response to disease and weeds, Erb compared standard soil applications of methyl bromide, 3 months of soil solarization before installing the black plastic, and no treatment. Solarizing took place in May through mid-August by laying down clear plastic in the exact location where the plants would grow.

Tests were run in the same plots in 1996 and 1998, with a fallow year in between. The plots were located in fields that had outbreaks of Phytophthora parasitica (the causal agent for Phytophthora root rot of tomatoes and peppers), "so it wasn't as if we were working on totally clean fields," Erb said. Verticillium wilt, leaf spot, and leaf blight can also be problems for Kansas strawberry growers.

Erb explained that the results can only be considered observational because he did not specifically inoculate disease organisms into the tests plots. He was interested in the system's potential to work without methyl bromide only as a sidelight to its practicality for strawberry production in the Great Plains.

Three years of data have shown no difference in yield between rows treated with methyl bromide or soil solarization or left untreated.

Having a break—a fallow time—rotating crops in the field, even planting a cover crop like marigolds, which are antagonistic to some soil nematodes, would also help minimize disease problems, he added. But Erb realizes that where the soil doesn't freeze as it does in the Midwest, a nonchemical pesticide system may not be as viable.

"If we combine some cultural practices—like this system, solarization, addition of compost, fallow times, and crop rotation—with disease-resistant cultivars, we could probably do without methyl bromide here except in fields that are notorious for disease problems," Erb said.

He believes it is important to look at how producers could manipulate the soil environment to grow strawberries without methyl bromide. "Research is not often able to examine long-term effects of a treatment. We need to look at production and soil condition 15 years down the road and see what is happening," Erb said.

But in the short term, Erb expects a chemical control is going to be a necessity for disease-susceptible cultivars, especially where the soil doesn't freeze or in fields that can harbor the fungi which cause root rot and vascular wilt diseases.

Husein Ajwa, a researcher at the ARS Water Management Research Laboratory in Fresno, California, has been at work with black, brown, and green plastic for weed control in a plastic and drip irrigation production system. He is also experimenting with direct application of pesticides other than methyl bromide directly through the drip irrigation system. (See Technical Report: Application of Methyl Bromide Alternative Fumigants by Drip Irrigation Systems for Strawberry Production in California, USDA Methyl Bromide Alternatives Newsletter, July 1999.)

Ajwa and his colleague Thomas Trout, research leader at the ARS lab, are taking advantage of an existing system of irrigation tape to directly apply a fumigant. The water in the irrigation system and the black plastic appear to minimize emissions from the fumigants.

In California, soil fumigation typically results in strawberry yields that are nearly double those from nonfumigated fields.

Last Updated: February 24, 2000