September Pasture To-Do List for Colorado Landowners: Soil Tests, Overseeding, and the 6-Inch Rule

September is Colorado’s pivot month. Summer stress is beginning to ease, cool nights are returning, and the soil is still warm enough for cool-season grasses to catch a second growth window before winter dormancy.

That window does not stay open for long.

For landowners around Parker and across the Front Range, the work you do this month can determine how well your pasture handles winter, how much grass returns next spring, and whether weeds such as cheatgrass gain another foothold. Back 40 Acres brings a lifetime of agricultural knowledge rooted in our family farm, along with decades of customer service experience, to help property owners make practical decisions for Colorado’s extreme climate.

Here is a straightforward September checklist for horse properties, residential acreage, vacant lots, and larger pastures.

1. Start With a Soil Test

Before applying fertilizer or choosing a seed mix, find out what your soil is actually doing.

Colorado State University Extension recommends taking soil samples from uniform areas of a field. A uniform area has similar soil type, slope, drainage, past management, and vegetation. If one section has a different history or soil condition, sample it separately.

For each uniform area:

• Take 15 to 20 soil cores

• Sample approximately 6 to 8 inches deep

• Avoid manure piles, old feed areas, fence lines, and unusual bare spots

• Place the cores in a clean bucket and mix them thoroughly

• Spread the composite sample on clean paper and let it air-dry

• Send the sample to a soil-testing laboratory in a clean container

Do not oven-dry the soil. Heat can change the test results. The CSU Soil, Water, and Plant Testing Laboratory is one option, and private laboratories that understand Colorado’s alkaline soils can also be used.

A soil test can help identify pH, salinity, organic matter, nitrogen, phosphorus, potassium, and other conditions that affect pasture growth. Testing is especially important before spending money on seed or fertilizer.

Why Test in Early Fall?

Early fall is a useful time to test established pastures because you still have time to make informed fertility decisions. It is also the best season to test phosphorus needs and topdress when the soil requires it.

Phosphorus moves slowly through most Colorado soils. Applying a soil-test-based phosphorus treatment in the fall gives freeze-thaw cycles and snowmelt time to move it into the root zone, where plants can access it as spring growth begins.

That does not mean every pasture needs phosphorus. Apply it according to test results and the goals for your field. Back 40 Acres can help coordinate fertilizer application as part of a broader pasture improvement plan instead of treating nutrients as a guess.

2. Decide Whether September Seeding Fits Your Property

Cool-season grasses often respond well to fall conditions because the soil remains warm while daytime temperatures moderate. That combination can support root development before winter.

The right timing depends on whether the ground is irrigated or dryland.

Irrigated Ground

According to the Colorado Forage Guide from CSU Extension, irrigated forage ground can generally be seeded 6 to 8 weeks before the first hard frost.

For Parker-area properties, that means watching the local forecast, elevation, irrigation availability, and the expected timing of a hard freeze. Do not rely on a calendar date alone. A site with reliable irrigation may have more flexibility than dryland ground, but young seedlings still need enough time and moisture to establish.

Dryland Ground

Dryland pasture is often better suited to dormant seeding from November through March. The goal is to place seed in the soil when it will remain dormant and be ready to use spring moisture when conditions improve.

Dormant seeding is not a guarantee. Colorado’s dry winters and unpredictable spring moisture can make establishment difficult. Still, it can be a practical option when fall moisture is unreliable and irrigated establishment is not available.

Seed-to-Soil Contact Matters

A seed sitting on top of hard ground is not a pasture plan. Good seed-to-soil contact is one of the most important parts of establishment.

Drilling is often preferred because it places seed at a consistent depth and presses it into contact with the soil. Broadcasting can work in some situations, but the seed should be lightly incorporated or rolled so it does not dry out, blow away, or become an easy meal for birds and rodents.

Back 40 Acres provides regenerative pasture seeding with professional equipment and site-specific planning. Learn more about our seeding services.

3. Consider a Fall Cover Crop, With Colorado Timing in Mind

For some properties, a fall cover crop can help protect soil, improve ground cover, and support nutrient cycling. At Back 40 Acres, we often emphasize options such as:

• Austrian Winter Peas

• Forage radishes

• Other site-appropriate cover crop combinations

Austrian Winter Peas can provide useful fall growth and contribute to a broader soil-improvement plan. However, they are susceptible to hard frosts in Colorado winters. Planting too late or relying on them in an exposed, frost-prone location can lead to winter loss.

That makes timing and site conditions important. Consider elevation, exposure, available moisture, expected frost, and whether the cover crop is meant for grazing, soil improvement, or temporary ground cover.

If you are using a herbicide program for cheatgrass or another weed before seeding, check the product label for reseeding restrictions and waiting periods. A good cover crop plan must work with the rest of your land-management plan.

Avoid Nitrogen During Establishment

Nitrogen can seem like an obvious way to push new grass along, but CSU Extension cautions against nitrogen during establishment in many situations, especially when interseeding or establishing grass-legume mixtures.

Extra nitrogen can feed weeds more effectively than young forage plants. It can also increase competition from existing vegetation and reduce the chance of new seedlings becoming established.

A soil test should guide fertility decisions. For more information, see CSU Extension’s guidance on fertilizing cool-season grasses and grass-legume mixtures.

4. Follow the 6-Inch Rule Through Late Fall

When it comes to land and pasture management, Back 40 Acres follows one clear rule:

Keep mowing height at 6 inches or taller.

Do not scalp a pasture before winter. Leaving grass 6 inches or taller helps:

• Protect grass crowns from temperature swings

• Shade the soil surface

• Hold moisture longer

• Reduce wind exposure

• Improve snow capture

• Reduce open space for weeds

• Protect root reserves going into winter

Taller grass also gives cool-season plants more leaf area to keep building strength while conditions allow.

Mowing still has an important role in September. Walk the property and identify weeds that are close to setting seed. Mow or manage those areas before frost when practical, but do not cut the entire pasture down simply to make it look uniform.

A healthy pasture should not look like a dirt lot or a closely clipped lawn. It should have protective cover and enough height to support the soil and the plants beneath it.

Back 40 Acres provides residential and pasture mowing for medium-to-large acreage, including overgrown fields, horse properties, and vacant lots.

5. Use September to Get Ahead of Cheatgrass

Cheatgrass is a fall-germinating winter annual. That makes September one of the most important windows to address it before a new crop becomes established.

Look for cheatgrass in:

• Thin or drought-stressed pasture

• Driveways and disturbed soil

• Fence lines and livestock access areas

• Vacant lots

• Bare slopes and eroded ground

• Areas where desirable grass has been grazed down

Late-season weed control is not just about appearance. Preventing weeds from setting seed helps reduce next year’s pressure and can improve fire mitigation around homes, outbuildings, roads, and property boundaries.

Rion uses products such as Plateau and Rejuvra, which contains indaziflam, as examples of fall-applied options for cheatgrass when the site, timing, vegetation, and product label allow. These treatments should be part of a larger plan: not a blanket application made without identifying the weed or considering desirable grasses.

Always follow the product label, including restrictions related to grazing, seeding, waterways, sensitive plants, and application conditions. For more background, read our guide to why fall is the window to stop cheatgrass before it takes over.

You can also learn more about our weed management and mitigation services.

6. Rest Pastures Before Winter

September is a good time to reduce grazing pressure and let pastures recover.

If animals have been using the same area throughout summer, rotate them to another paddock or provide a sacrifice area while the pasture rebuilds. Do not graze into the dirt before winter. Bare soil is more vulnerable to erosion, drying, weed invasion, and temperature swings.

For horse properties, pay close attention to high-traffic areas around gates, water tanks, feeders, and shelter. These locations often need separate management because horses can quickly remove the protective grass cover.

A simple fall grazing plan may include:

• Rotating animals between available areas

• Giving recently grazed pasture adequate rest

• Keeping grass cover at 6 inches or taller where practical

• Limiting access when soils are wet

• Moving animals before repeated grazing weakens the same plants

• Planning supplemental feed before the pasture is depleted

Healthy soil and healthy forage depend on recovery time. Rest is not wasted pasture: it is part of maintaining the pasture you want next year.

Your September Checklist

Before the month gets away from you:

• Sample each uniform pasture area

• Take 15 to 20 soil cores at 6 to 8 inches

• Air-dry and send samples to a qualified lab

• Review phosphorus and fertility recommendations

• Schedule fall fertilizer application if the soil test supports it

• Decide whether irrigated overseeding or dryland dormant seeding fits

• Plan cover crops carefully, especially Austrian Winter Peas

• Maintain mowing at 6 inches or taller

• Mow weeds before they set seed

• Check for fall-germinating cheatgrass

• Rest and rotate pastures

• Keep livestock from grazing into bare dirt

• Schedule land work before winter weather limits access

Let’s Chat About Your Colorado Acreage

September is a short but valuable opportunity to improve your pasture before winter arrives. Whether you own a horse property near Parker, a residential acreage, a vacant lot, or a larger pasture, Back 40 Acres can help you evaluate your options and build a practical plan.

Our approach combines a lifetime of agricultural expertise, regenerative seeding methods, fertilizer application, mowing, weed mitigation, aeration, and erosion control. We are fully insured, reliable, professional, and committed to completing work well and on time.

We are happy to discuss your property and work within any budget.

Request a free quote or let’s chat:

• Phone:720-730-4040

• Email:rion@back40acres.com

• Location: Parker, Colorado

• Website:Back 40 Acres