Petroleum County Soil Data
Petroleum County, Montana
USDA SSURGO / PHZMAvg pH
7.4
Texture
Clay Loam
Drainage
N/A
Organic Matter
1.7%
Hydrologic Group
N/A
Data Story
About Soil in Petroleum County, Montana
Naturally Alkaline Plains Soil
The soil pH here averages 7.39, which is slightly less alkaline than the Montana average of 7.43 but above the national 6.5 median. The county's soil score is 37.8, reflecting its unique prairie challenges.
Silt and Clay Dominance
With 30.7% clay and 39.2% silt, these soils are heavy and retain moisture longer than sandy profiles. Sand makes up 30.1% of the mix, providing some necessary structure.
Lower Organic Matter Levels
Organic matter levels are 1.71%, trailing both the national 2.0% average and the state 2.54% average. The water capacity of 0.161 in/in is nearly on par with the Montana average.
Heavy Soil Management
Though specific drainage classes are not listed, the high clay content suggests slow drainage and high moisture retention. Be mindful of compaction if working the soil while it is wet.
Short-Season Success in 4b
Zone 4b favors short-season crops like peas, radishes, and certain grains. Focus on adding compost to boost organic matter and improve your garden's overall health.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Hydrologic group data not available.
Drainage Class
Drainage class data not available.
Soil Profile
Dominant texture: Clay Loam
Typical soil profile. Actual depths vary by location.
USDA Soil Orders
Clay Soil Detected
Clay soils can struggle with drainage. These products improve soil structure and water flow.
Browse Soil AmendmentsFrequently Asked Questions
What type of soil does Petroleum County have?
Petroleum County's soil is classified as Clay Loam. This indicates the relative proportions of sand, silt, and clay — 30% sand, 39% silt, and 31% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Petroleum County's soil acidic or alkaline?
Petroleum County's soil has a pH of 7.4, which is near neutral. This range is ideal for most garden plants and field crops.
What is the drainage class for Petroleum County?
Drainage class data is not currently available for Petroleum County.
What crops or plants grow well in Petroleum County's soil?
Based on Petroleum County's Clay Loam texture, pH of 7.4, and drainage class, the soil is well suited for drought-tolerant crops and native grasses, row crops and vegetable gardens.
What USDA soil order is found in Petroleum County?
The dominant USDA soil order for Petroleum County is not currently available in our dataset.
Soil & Planting Advisory: Petroleum County
Soil Verdict
Petroleum County is in USDA hardiness zone 4b, a cold climate zone. where winter lows can reach -25°F. Soils here experience deep freeze cycles that can disrupt structure, kill shallow roots, and slow microbial activity for months each year.
Planting Guidance
Focus on cold-hardy perennials, native grasses, and conifers. The short growing window favors plants with low heat requirements. With extreme winter lows, any marginally hardy plants need heavy mulch and wind protection. Always match plant selections to the specific microclimate of your property — low spots, slopes, and wind exposure can shift effective hardiness by half a zone.
Soil Implications
Deep winter freezing can create soil heaving that pushes shallow-rooted plants out of the ground; add 3-4 inches of organic mulch each fall. Soil drainage is critical — frozen, waterlogged soil kills roots faster than cold alone. When soil temperatures drop below freezing, microbial nitrogen cycling stops; spring fertilization is more effective than late-fall application.
Regional Context
Petroleum County closely matches the Montana average hardiness conditions.
Planning your lawn? View lawn care data for Petroleum County on LawnByCounty.com →
Other Counties in Montana
Soil data sourced from USDA SSURGO via Soil Data Access. Data is informational only and should not be used as a substitute for on-site soil testing. Contact your local NRCS office for site-specific soil information.