How to retrieve the most from your soil test

A soil test can be a very effective tool in a producer’s toolbox. It can tell you the kind of nutrients that are available and the amounts that are present. Really, it is the foundation of any plan to improve the output of your pastures.

Knowing the amount of nutrients present can be beneficial when it comes to choosing what type of fertilizer to use. If correctly done, soil sampling and testing can indicate the types and amounts of fertilizer and lime that you should put out. With this knowledge, you can make the most economical decision.

Now you may be asking how it is that you can do a soil test properly. Well, here are some points that you may want to consider:

What does a soil test do?

As I mentioned above, a soil test can determine your soil’s current health and fertility. Certain nutrients will be lacking in your soil no matter where you are. The soil test can pinpoint any nutrient deficiencies that you may have.

Determining which nutrients are lacking in your soil is a crucial piece of information for pasture improvement. Just this fact alone can translate to saving you money in fertilizer costs. By having that knowledge, a producer can then decide on the fertilizer that will have the most impact. By choosing the best investment, a producer won’t be wasting money on things they do not need.

You can improve the yield of a pasture by applying the nutrients that are lacking. Conversely, if that specific nutrient is already highly available, fertilization will result in little, if any, increase in yield.

How do I do a soil test?

Getting a sample bag to send off for testing is the first step to conducting this test. Any fertilizer provider will also have kits available that you can use. Your local county extension office will also have this for you.

Now that you have the bag, it is time to get your hands dirty.

Collecting the samples

To get an excellent overall reading, you must collect multiple samples from each pasture that is to be tested. In fields of up to 40 acres, collect 10 to 15 samples.

Courtesy of Texas AgriLife Extension

The soil sample should be representative of the overall area in question. If you have different pastures with different types of terrain, you will need to test them separately.

Avoid collecting samples from high-nutrient areas like ditches and feeding areas. This reason is because those will not give you an accurate reading of the whole area.

It is recommended that you collect soil from 6 inches below the soil surface. The soil surface is the top that you can see after you have moved away all of the plant material. I go into detail about how to get the best result from this test in a previous post, “5 tips to get the most out of your soil test”.

Mixing the samples

Once you have collected the samples, mix all of the samples together in a clean bucket. If you are taking multiple samples from different areas, then you will want to use multiple buckets. After the samples have been mixed, remove any present plant material because this can mess with your results.

You will want to put about 1 to 2 cups of the mixed soil into the container that you have. If you picked up your bag from the county extension office, then all you will have to do is fill the bag completely.

After doing this, be sure to fill out all of the information on the sheet that is provided and send it off to be tested.

Selecting the proper soil test

Part of the information that you will be filling out is selecting the type of soil test that you want. There are multiple ones to choose from, which can vary in price. Typically, here in Texas, it can range between $12 and $32 per sample.

Here are some of the tests that you can choose from:

• Routine: this is the basic test that you can choose from. It will determine the soil pH, salinity, nitrates, and levels of the primary nutrients (Phosphorus, Potassium, Calcium, Magnesium, Sodium, and Sulphur) that are available. It will also provide the Basic N-P-K fertilizer recommendations. This test is acceptable for most applications.
• Micronutrient: this test estimates the levels of Zinc, Iron, Manganese, and Copper that are available. You should use this test for specialty crops in high-pH soils where corn or sorghum is being grown. You can also use this test to troubleshoot any deficiencies.
• Boron: this soil test determines the level of water-extractable boron in the soil. You will want to use this test where clover, alfalfa, or other legumes are grown on sandy soils.
• Detailed salinity: This test measures the pH, electrical conductivity, and water-soluble levels of the major cations in the soil. You can conduct this test if water quality is of concern.
• Lime requirement: this one determines the amount of lime that will be needed to raise the soil’s pH to a desired level. This test is required on very acidic soils where alfalfa or other legumes are grown.
• Texture and organic matter: This is a specialty test for specific applications. It will determine the amount of sand, silt, and clay in the soil. This test is generally requested for environmental or research purposes.

Reading the results

The type of test that you are wanting will determine just how long it will take you to get the results back.

The routine test can take up to 5-7 days to get the results back. As you may guess, the more in-depth analysis will take longer to get back to you. You can get the results back either by mail or email, it’s entirely up to you.

Depending on where you send the samples off to or which state you are in, you can get some differences in results. This difference occurs due to the different types of testing methods.

While the basic information you’ll receive will show the soil’s pH level and whatever nutrients it contains, most of the time, your test results will also include any recommendations for application to improve your soil.

How to apply your results

One of the essential results of this test will be your soil’s pH. It is the measure of the active acidity or alkalinity in your soil. Most forages prefer a soil pH between 6.0 and 8.2. You will need to apply something like calcium carbonate to increase the pH. You will be able to tell if you need lime and how much to use after the test. It may take a few weeks for the lime to absorb into the soil thoroughly. This slow absorption means you must apply it way before you plan on putting out any fertilizer.

Another recommendation on the results will be for Nitrogen, Phosphorus, and Potassium. Nitrogen is the most crucial component for plant growth and will give plants energy to grow. Phosphorus is essential for root growth and development, so if you are planting new forages, this will be important. Potassium increases the plants’ ability to handle stress with a healthy root system.

Next, soil organic matter is basically the same as the soil carbon. It is a reflection of the overall soil health. It is in equilibrium with climate, soil mineralogy, and the environment so that it can fluctuate. Monitoring the soil quality over several years will indicate whether it is improving. This monitoring is why it is vital that you perform a soil test every three years to monitor how things are improving for you.

Suppose you would like more information on soil tests. In that case, you can visit the Texas A&M Extension Service Soil, Water, and Forage Testing lab by clicking here.