Getting the dirt on good gardening

Soil is the root of all success in local gardens

Posted: Sunday, July 16, 2006


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  Photo by M. Scott Moon

Photo by M. Scott Moon

Why is it that some people on the Kenai Peninsula can grow beautiful lawns and productive gardens and others can’t?

It really depends on what’s on the ground — dirt.

A nicer word for it is soil, and the type of soil the glaciers left behind determines what can and cannot be grown here.

“Soil is the foundation for all plants,” said Dan Sexton, a former geology student and former partner in Trinity Greenhouse on Kalifornsky Beach Road.

He said soil is where plants get nutrients, and its consistence regulates the amount of oxygen and water delivered to the growing plants.

“Soil per se is ground rock,” said Tom Jahns, University of Alaska Fairbanks Cooperative Extension Service land re-sources district agent.

Jahns said glaciers played — and still play — a huge part in the type of soil that’s here. “Our soils are in their infancy.”

Sexton couldn’t agree more.


Rosemary Kimball is dwarfed by the rhubarb she harvested from her garden in Sterling last week. "You can't fertilize it too much," she said of the sour plant.

Photo by M. Scott Moon

“It takes hundreds, if not thousands of years to create topsoil,” Sexton said.

“We don’t have a lot of true topsoil ... only about eight inches,” he said.

By contrast, areas of the Mississippi River Valley have as much as 10 feet of topsoil.

Beneath the eight inches of topsoil typically found in the Kalifornsky Beach area is gravel and then two feet of clay.

“This was identified as a good agricultural area,” Sexton said.

Soil is made up of any combination of clay, silt and sand. Clay contains the finest particles and sand is the coarsest.

What gardeners should strive for is something in the middle — a sandy loam mix, according to Sexton.

A brochure available from the Cooperative Extension office on Kalifornsky Beach Road describes sandy loam as containing mostly sand, but with enough silt and clay to make it somewhat cohesive.


Philip and Rosemary Kimball grind compost for their garden last week. The Kimballs said that good dirt is one of the secrets to their prolific garden.

Photo by M. Scott Moon

“If squeezed when moist, it will form a cast which will withstand careful handling without breaking ... .,” the brochure states.

Sexton said clay, which contains the finest particles of silt, does not allow oxygen to get to the roots of plants.

A good gardening soil needs plant materials that allow for drainage.

“As water soaks through, oxygen is pulled into the substrate,” Sexton said.

He suggested people dig out the clay and blend peat moss into heavy soil if they desire a lawn or garden, or bring in eight inches of good topsoil.

“We have peat bogs on the Kenai Peninsula, one in Sterling and one off Beaver Loop,” said Sexton. “People can bring in peat and blend it into their soil.”

The extension office has an extensive list of sources of peat on the Kenai Peninsula.

Jahns said the Master’s Mix, manufactured by Trinity Greenhouse, “is an excellent product”; Fishy Peat, developed by the Poindexter family, is available from the Anchor Point Greenhouse; Stuart Northrup in Sterling is a new source for peat and topsoil; and Jam VanOss in Homer offers peat products.

“Some people try two or three inches (of topsoil). That’s not enough,” Sexton said. “For a garden, you need a foot.”

Short of bringing in all topsoil, Jahns said, “The best we in Alaska can do are silt loams.”

Soil sampling

Jahns recommended people planning a lawn or garden begin by taking a soil sample and having it professionally tested in a lab to measure its acidity and the presence of macro and micronutrients.

Macronutrients that will be measured are nitrogen, phosphorus and potassium.

The lab will also test the soil’s alkalinity.

On a scale of 1 to 14, “you want a pH of 7,” said Jahns.

A high pH of 14 means the soil is alkaline. A low number means it is acidic.

Jahns said at a pH of 7, all nutrients are available to plants.

A number of labs around the country provide soil tests, for a fee, but Jahns said not all do testing relative to conditions in Alaska.

The one lab he recommends is Brookside Laboratories in New Knoxville, Ohio. People should request soil test package S001AN to get meaningful results for this area.

Using a clean shovel and a clean five-gallon bucket, people should take six to 12 random samples from all around one acre of land where a lawn or garden is to be placed, according to Jahns.

“Make sure it’s representative of what the entire plot is or it’s meaningless,” he said.

Slices of dirt up to six inches deep should be placed in the bucket, removing all organic matter.

The dirt should be mixed well and air-dried.

Jahns cautioned the collected dirt should be protected from contamination by the family cat.

After the dirt is dry, about two cups of dirt should be placed in a waxed paper or paper bag. The labs frown on using plastic bags.

The bag of dirt should then be placed in a strong mailing envelope, along with a check for $16.50 and a soil sample information sheet (available at the extension office), and mailed to Ohio.

The lab will send back a report containing a long series of numbers, which need to be deciphered by someone like Jahns at the extension office.

He will then make recommendations about the amount of lime or other fertilizers that need to be added to the soil.

“Most of our soils are pretty acidic,” Sexton said. Clay is acidic.

The soil test will indicate whether lime needs to be added to bring up the pH level from highly acidic to strongly alkaline.

Sexton cautions that adding too much lime over the years will necessitate reversing the process to return the soil to acid.

Besides the highly acidic clay in the central peninsula, another plentiful source of acid are spruce tree needles.

Sexton does not recommend using them in garden beds, as too much will ruin garden soil.

He also said, “If you burn spruce (in wood stoves), be careful where you put the ash. It could be too acidic for the garden.”


Adding nutrients to the soil by way of composting is the choice of many area gardeners, but the greatest benefit of composting is improving the soil’s physical characteristics.

Composting with plant and animal residue improves aeration, root penetration and water infiltration, according to the extension office.

Alaska presents some challenges to the compost task, however.

In warmer climates, using a wooden or even cement box for the compost pile is preferred. In Alaska, the moisture collected at the bottom of the pile often freezes into a solid block, and may not thaw completely during summer.

Creating a compost pile in an open, well-drained area that receives the most heat from the sun is best.

Additionally, using fish heads and other fish waste as compost material — while a good source of nutrients — attracts bears and eagles.

Fish waste can be used, but if it is, a hot, fast compost method is preferred over the much slower, natural way, according to Jahns.

Other materials for the compost pile could include grass clippings, sawdust and tall weeds or old flower stalks.

“Compost makes sandy soil hold water and improves drainage in clay soils by creating air spaces,” said Jahns.

The extension office also offers a pamphlet on composting with worms, which can turn kitchen waste into a rich compost.

Adding nutrients

“Our native soils are generally low in nutrients, such as boron,” said Sexton.

“If people add peat or topsoil, they also need to add nutrients through manufactured fertilizers,” he said.

Fertilizer packaging indicates the proportions of nitrogen, phosphate and potash present.

According to Sexton, a fertilizer marked 8-32-16 is good for flower gardens and new lawns; 16-16-16 is a good general-purpose fertilizer; and 22-4-4 is good for an established lawn.

Jahns said organic nutrient sources are identical to synthetic forms, whether they are manufactured by a company such as Agrium or come from steer manure. Synthetics, however, do not contain the micronutrients.

To adjust for the micronutrient boron, Sexton said, “We use boraxo soap.

“One-half teaspoon per two gallons of water is enough for the entire season,” he said.

Finding help

Many questions about soil for lawns and gardens can be answered by the Cooperative Extension Office, and Sexton said Trinity Greenhouse, which has been in business on the Kenai Peninsula for about 30 years, works hand in hand with people who are putting in lawns and gardens.

“Soil is the medium in which plants acquire nutrients, oxygen and nitrogen,” Sexton said. “You must start with good soil.”

Good dirt

Looking for loam to get your garden growing? Try these products and services:

· Master’s Mix, manufactured by Trinity Greenhouse.

· Fishy Peat, available from the Anchor Point Greenhouse.

· Stuart Northrup in Sterling is a new source for peat and topsoil.

· Jam VanOss in Homer offers peat products.

“The foolish man seeks happiness in the distance,the wise grows it under his feet.”

— James Oppenheim

“The poetry of the earth is never dead.”

— John Keats

“A nation that destroys its soils destroys itself. Forests are the lungs of our land, purifying the air and giving fresh strength to our people.”

— Franklin D. Roosevelt

“Nature is not a place to visit, it is home.”

— Gary Snyder

“When you throw dirt, you lose ground.”

— Texas proverb

“Heaven is under our feet as well as over our heads.”

— Thoreau

“I have a rock garden. Last week three of them died.”

— Richard Diran

“To forget how to dig the earth and to tend the soil is to forget ourselves.”

— Mahatma Gandhi

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