A soils primer for Homer: Kachemak soils have wonderful properties

Kachemak soils are the dominant soils on the rolling hills in the Diamond Ridge area. (Photo courtesy Doug Van Patten)

Kachemak soils are the dominant soils on the rolling hills in the Diamond Ridge area. (Photo courtesy Doug Van Patten)

This is the second installment of the series, “A Soils Primer” for the Homer area. This is meant to be a non-technical, for the most part, introduction of the Fab Four of Homer soils.

The rolling hills that stretch north from the bluffs above Homer to the Deep Creek watershed are predominately cloaked by grasslands, fireweed and scattered stands of spruce. These soft hills are blanketed by Kachemak soils. Those of us that have had the good fortune to live with these pleasant soils can attest to some of their wonderful properties. For those of you that have only worked with poor soils, scripture says nothing against coveting thy neighbor’s soil. While this series of articles focuses on soils, the ecologist Aldo Leopold noted, “Land is not merely soil, it is a fountain of energy flowing through a circuit of soils, plants and animals.”

So where do these soils come from and how did they form? Out to the west across Cook Inlet stand the volcanoes of the Alaska Range. Usually these silent sentinels are just that: silent. Occasionally they roar to life, reminding us that they are geologically active. My introduction to volcanism was on the morning of March 27, 1986 when Augustine Volcano erupted. A huge menacing black cloud soon enveloped Homer and spread rapidly to the north. Then the billowing clouds began dropping their gritty abrasive cargo. For many of us this rude introduction provided a reality check on the nature of volcanic ash. Some of the immediate effects were irritation of eyes and lungs, if not protected, and havoc to internal combustion engines. Lingering effects were often encountered when attempting to cut gritty lumber or wood from uncovered stacks and cleaning clogged roof gutters and footer drains for months or longer. On the bright side, new soil was being formed.

There are five interacting soil forming factors: parent material, climate, landscape position, living organisms and time. Parent material is a dominate factor in the formation of Kachemak soils and is responsible for many of its properties. The topsoil and underlying couple of feet of these soils (the solum) is composed of weathered volcanic ash with varying amounts of wind deposited glacial silt from outwash plains of receding glaciers. This accumulation has been an ongoing process, on stable landforms, for thousands of years. The substratum of these soils is glacial till or the stratified Tertiary deposits of the Kenai Formation. The volcanic ash from our local volcanoes is composed dominantly of silica in the form of volcanic glass that weathers rapidly into an amorphous soil material. It has unique properties including low bulk density, high porosity and an affinity for organic carbon. These properties make these soils easy to till, quick to drain after rainfall events, and provide exchange sites for holding and releasing nutrients to the plants. The thick dark brown solum gives the appearance that these are soils with a healthy soil biome. That first impression is correct. Gardeners love these productive soils that are without rock fragments, poor drainage and high clay content. Contractors also love these soils. They are easily excavated and normally do not have a water table within 6 feet of the surface.

Soils are no different from other components of the natural world, or human nature. They also have their faults. In addition to an affinity for organic carbon, these volcanic ash soils also have an affinity for phosphorous. They bind it tightly and make it unavailable for the plants. These soils are also acidic and naturally infertile. This can be easily remediated through liming and fertilization.

It is more difficult to mediate the physical properties of the solum. The amorphous material has a “card house” or random structure that has low shear strength and bearing capacity. Thus, they are not suitable as a base for foundations or pilings. This material, with high organic carbon, is better suited for lawns and gardens.

Compaction of the solum is an issue from heavy traffic on well used trails. The Watermelon and Homestead trails are examples that are great when they are dry. However, they can be as treacherous and slippery as ice when wet.

If you are interested in the technical details of soils a wealth of information is available from Natural Resources Conservation Service (NRCS) at https://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/survey. Soil Survey reports and maps for the Western Kenai Peninsula (Homer to Point Possession), the Lower Kenai Peninsula (Jakolof Bay to East Chugach Island), and most counties in the United States are also available through the link above.

The U.S. soil survey program began in 1899 and continues today. Surveys are updated as technology develops.

Doug Van Patten, a retired soil scientist, had the pleasure of exploring, classifying and mapping soils throughout Alaska, and parts of Montana, Hawaii and Florida for 40 years.

He moved to Alaska in 1976 from Montana, worked as a soil scientist/project leader for 30 years with USDA/NRCS, followed by 10 years of part-time work as a senior soil scientist with various private consulting firms including HDR Engineering and Three Parameters Plus, Inc.

More in News

Alaska State Troopers logo.
Anchor Point house fire leaves one dead, one in serious condition

The cause of the fire is under investigation.

Snow and debris from an avalanche can be seen near Mile 45 on the Seward Highway on Monday, March 29, 2021. (Photo courtesy Goldie Shealy)
Center promotes avalanche awareness

The Chugach Avalanche Center in Girdwood will begin its daily forecasts Saturday.

Commercial fishing and other boats are moored in the Homer Harbor in this file photo. (Photo by Michael Armstrong/Homer News)
Seawatch: Historic sockeye run predicted for Bristol Bay

ADF&G says 2022 run could break this year’s record

The entrance to the Mendenhall Glacier Recreation Area in the Tongass National Forest was covered in snow on Friday, Nov. 19, 2021, a day after federal authorities announced the next step in restoring the 2001 Roadless Rule on the forest. (Peter Segall / Juneau Empire)
Feds put freeze on Roadless Rule rollback

On the Roadless Rule again.

Alaska man pleads not guilty to threatening 2 US senators

If convicted, he could face a maximum sentence of 50 years in prison.

Commercial fishing vessels are seen here on the Kenai River on July 10, 2020. (Photo by Brian Mazurek/Peninsula Clarion)
Fishing industry takes a hit during pandemic

Overall fish harvesting jobs in Alaska dropped by the widest margin since 2000 — 14.1% — in 2020.

FILE - The Olympic rings stand atop a sign at the entrance to the Squaw Valley Ski Resort in Olympic Valley, Calif., on July 8, 2020. U.S. Interior Secretary Deb Haaland on Friday, Nov. 19, 2021, declared "squaw" to be a derogatory term and said she is taking steps to remove the term from federal government use and to replace other derogatory place names. The popular California ski resort changed its name to Palisades Tahoe earlier this year. (AP Photo/Haven Daley, File)
Interior secretary seeks to rid U.S. of derogatory place names

ALBUQUERQUE, N.M. — U.S. Interior Secretary Deb Haaland on Friday formally declared… Continue reading

Most Read