Will Your Soil Pass the Test?
Posted in Soil and Amendments on March 22, 2015
Plants get the vital nutrients needed for health and growth from the soil. Soil testing is a means of determining whether there are nutrient deficiencies or surpluses, soil pH, and Cation Exchange Capacity (CEC).
Soil can be treated, or amended, based on the soil testing results. Amended soil is more likely to produce healthy, vigorous plants. Soils that are nutrient deficient or of the wrong pH, increase the chances your plants will be damaged by disease, pests, and drought, to name a few.
The acidity or alkalinity of soil is described as the soil’s pH level. High pH translates to highly alkaline and low pH translates to highly acidic. When the soil’s pH is balanced (at around 6.5), most essential nutrients are soluble and ready to be absorbed by your plants. Different species of plants need different pH levels for optimum health. Typically, shrubs, flowers, and turf grass benefit the most when the soil has a pH of between 6.0 and 7.0.
When pH is below 6.0, certain elements (manganese and aluminum) are more soluble. That means your plants are more able to absorb them and this can result in toxicity, which causes stress and failure.
The other end of the spectrum results in reduced nutrient solubility and something called micronutrient lock-up (specifically, iron, magnesium, and calcium). These soils often have higher levels of sodium which results in poor soil structure.
In addition to the lock-up of valuable nutrients, water and other nutrients can’t easily penetrate poorly structured soils. This can also result in plant stress and failure, water waste, and run-off.
Changing Soil pH
You can raise or lower soil pH with lime and sulfur, respectively.
The best type of lime for raising soil pH is the pelletized version. It’s easier to apply, breaks down with water, is less dusty and works more quickly that granular lime. Depending on the nutrient levels of your soil, you may need either dolomitic (magnesium) or calcitic (calcium) lime.
If you need to lower soil pH you can do this using sulfur. The soil test results will tell you how much you should use. Soils with higher amounts of “free lime” (free calcium carbonate) will need a larger amount of sulfur to successfully lower their pH.
Collecting a proper soil sample is crucial to getting your soil the proper amendments. The cause of most errors in soil testing is improper sampling. Over- or under application of fertilizer and other amendments is the result of poor samples.
How to Collect a Proper Sample
- Each sample should be one to two cups of soil.
- Every area in question should have its own sample.
- All samples should be clear of thatch, mulch, plant tissue and surface debris.
- Areas up to 10,000 square feet require ten to twelve cores taken from random locations. These cores should be put in the same sample bag to create a composite sample.
- Areas over 10,000 square feet require one extra core for each additional 1,000 square feet.
- Areas that have different soil texture, color, and plant types planned for planting should have separate samples for each section.
- Do not sample areas that were recently amended or fertilized.
- Sample turf three inches below the thatch later.
- Sample soil around trees, shrubs, and ornamentals six to twelve inches deep. Take cores from inside and just outside the drip line.
The fertilizer industry, independent consultants, and university agronomists recommend soil testing as an agronomic Best Management Practice (BMP). They believe it provides the following benefits:
- Promotion of good industry stewardship
- Reduces lost fertilizer caused by nutrient lock-up
- Allows for nutrient uptake optimization through corrective actions
- Tracks nutrient and pH levels in landscape and turf soils
- Increases soil quality which prevents run-off, allows for better nutrient absorption and reduces water waste
- Provides information that helps customize fertility programs
- Makes your landscape healthier and beautiful
You can pick up your Soil Test Kit at your local Hydro-Scape Branch. Our experienced staff will be happy to answer any questions you have.