Example Article for Broadwater County Extension Agent
Demystifying Soil Amendments
 | Author:
Allison Kosto, MSU Broadwater County Extension Agent
MSU Broadwater County Extension Agent |
Demystifying Soil Amendments
Allison Kosto
MSU Broadwater County Extension Agent
A quick Google search and you can find ideas for soil amendments… too many ideas. There are many options and a wide range of opinions. Understanding the biology of soil and the unique climate of Montana and Broadwater County is important to narrow down the options.
Soil is a complex living ecosystem that contains water, oxygen, microorganisms and nutrients. A soil amendment is a material that is added to the soil to improve the physical properties of the soil and/or enhance nutrient availability. Benefits of amendments include water retention, water infiltration, drainage, aeration and structure. It is important to understand why you amend and use specific strategies or materials to meet your needs.
Before you amend, a soil analysis is extremely valuable. A soil analysis provides a platform to make decisions for soil amendments and fertilizers. A basic soil test costs $15 to $20 per sample. Your local MSU Extension Office can provide information on how to collect a sample and where to send it.
If you don’t get a soil analysis, there are a few assumptions we can make. Nitrogen is highly mobile in the soil, so deficiencies are common and nitrogen fertilizer is typically needed. On the other hand, phosphorus and potassium are less mobile and deficiencies are less common in our area. Let’s look at some common soil amendments.
Livestock Manure
Manure is easy to find. Options include fresh manure, aged manure (stockpiled) and composted. Aged or stockpiled manure is most common but composted is ideal. Composted manure goes through an active heat cycle that kills most pathogens and weed seeds. If you use stockpiled manure, wait at least one year but longer is better. Do not use fresh manure. Herbicide residual can be an issue with all types, so know where your manure came from.
Manure is high in potassium, which is generally not needed in large amounts. Fortunately, high potassium typically doesn’t cause a lot of major problems, but it can disrupt the uptake of other nutrients such as magnesium, zinc and iron. If you add manure to increase nitrogen, it takes a lot. To add 2 pounds of actual nitrogen to a 1000 square foot garden, it takes about 115 pounds of beef manure. Poultry manure is higher in nitrogen than that of other animals.
Green Manure
This is the use of short-lived crops with the purpose of integrating more organic matter into the soil. Common green manure crops include clover, small grains, field peas, buckwheat and radishes. The type of crop can be specifically selected to target certain benefits. For example, legumes can fix nitrogen in the soil. The crop is then mowed or terminated at some point during the growing season and eventually tilled into the soil to add organic matter.
Peat
Peat moss is a good option for adding organic matter. Organic matter (determined by a soil analysis) should be about 4-6%. Peat contains little nutrients but does help the soil hold water and will break down over time.
Compost
There are many types of compost. You can purchase it or make your own. A plant-based compost is typically recommended as it will add more organic matter and nitrogen to your soil. Examples are composted lawn clippings, leaves, food scraps, straw and so on. As we already discussed, manure-based composts add a lot of potassium, which isn’t necessary in our area. Herbicide residual can also be an issue with any type of compost.
Wood Ash
This is not recommended for Montana gardens. Ash raises the pH in the soil and is high in salts and potassium. In Broadwater County, our soils are already alkaline (high pH), so ash continues to raise the pH to an unproductive level over time. Ash can be a better soil amendment in areas of the country with highly acidic soil.
Other amendments such as lime, gypsum, perlite and vermiculite are rarely needed unless a soil analysis says otherwise. Nitrogen fertilizer is often needed in addition to soil amendments. High nitrogen fertilizer options include synthetic high nitrogen fertilizers, blood meal, fish meal or cottonseed meal. Micronutrient fertilizers are rarely needed, especially with a good organic matter regime.
For more information on soil amendments or if you need help with a soil analysis, you can find the MSU Extension Office in Broadwater County at 416 Broadway, Townsend or contact us at 406-266-9242 or allison.kosto@montana.edu.
