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David Granastein, sustainable agriculture specialist at Washington State University, takes a close look at the ingredients in Kyle Mathison’s compost. Cherry waste from Stemilt’s packing lines has just been added.

David Granastein, sustainable agriculture specialist at Washington State University, takes a close look at the ingredients in Kyle Mathison’s compost. Cherry waste from Stemilt’s packing lines has just been added.

Kyle Mathison has taken composting to a new level, with an 18-acre on-farm composting facility to supply his 1,200 acres of cherries, apples, and pears  at Stemilt Hill near Wenatchee, Washington.

Mathison, a grower and partner in Stemilt Growers, Inc., Wenatchee, began growing cherries organically a decade ago. Now, about a third of his 1,000 acres of cherries are certified organic.

At first, he bought compost from Canada or Yakima, Washington, to enrich the soil, but found transportation too expensive. So, in 2005, he began making his own “designer compost” and now makes enough to treat his entire acreage, not just the organic. It’s all part of his effort to grow fruit with great ­flavor that people remember.

“We call it Stemilt World Famous Compost,” Mathison said. “World Famous is not a destination. It’s a journey. Every day you have to work hard to get there.”

Most of the 22,000 tons of raw material his facility processes annually come from local sources. Several years ago, he opened the Stemilt Organic Recycling Center in Wenatchee, which receives and grinds up waste from homeowners and the local waste management company. This is waste that would otherwise go to the landfill, Mathison noted. In the spring, it is made up of about 80 percent brush and 20 percent grass. In the summer, the proportions are reversed.


Mathison transports the yard waste to his compost facility, where it is mixed with other ingredients, including: horse manure from a local stable or dairy manure, apple waste from the slicing company Crunch Pak, and leaves and fruit waste from Stemilt’s packing houses. Wood chips are added for aeration.

The compost is turned and wetted when it reaches a temperature of about 142°F. “It’s kind of like cooking a medium-rare steak,” Mathison explained. “We don’t want it to be underdone or overdone.”

At first, the compost typically needs turning every two to three days, as it reaches the temperature threshold. Later, it might need turning only once a week, or every ten days as the composting process slows down. In the winter, it’s not turned at all. In the summer, the process can take as little as six weeks. In winter, it can take six months. When it’s finished cooking, nutrients, such as calcium, sulfur, and zinc, are added as needed.

Mathison said he bought several loads of crab shells from the ­Washington coast as a source of calcium, which is important for disease resistance, but had to stop when neighbors complained about the smell.

His facility is certified by the Washington State Department of Health and the Department of Ecology. It includes leaching ponds to catch the runoff from spring snow melt. Water from the ponds is applied to the trees during the dormant season.

He makes both organic and conventional versions of the compost. Lawn clippings, which can contain heavy metals, are kept out of the organic. He sells compost to other growers but uses most of it on his own orchards.


Mathison applies 8 to 12 tons per acre of compost per year, half in the spring and half in the fall, with weak trees getting 10 to 20 tons. In the spring, the cherries also receive two applications of fish fertilizer, and then compost tea (applied to the ground) and molasses to give the trees a jump-start. It’s important to hit cherries hard with the nutrients, he said, because of the comparatively short growing season. The trees receive 60 gallons of compost tea per acre—two applications of 20 gallons in the spring and one in the fall.

“I think a lot of this is art,” he reflected.

Mathison brews his own compost tea from vermicompost, bat guano, fish fertilizer, and molasses using an Earth Tea Brewer. Air is pumped into the brewer to prevent the mixture from stagnating.

In the dormant season, he applies fish oil, which he imports by the container load from Chile and also sells to other growers.

Mathison said growing practices in his conventional and organic blocks are similar. Since applying compost, he’s not needed to use as many pesticides or conventional fertilizers in his conventional blocks. Conventional and organic fruit growing are becoming closer and closer, but the big difference is weed control. He uses Roundup (glyphosate) in his conventional blocks but a black fabric mulch in the organic blocks.

The one area that is not yet sustainable is labor, said Mathison, who needs 600 workers to hand pick his 7,000 tons of cherries. Employees can make $120 to $150 a day.

“I don’t know how long they’re going to keep coming,” he said. “We have beds for about 490. That helps a lot, but labor is probably the most unsustainable part of this operation.”