Performing a soil test is one of the most underutilized range management tools. Knowing your soil’s fertility and what nutrients are provided is crucial. Often times producers just put out the same fertilizer they always have and hope for the best.
Soil fertility and health is important for forage production. When forage production is increased that means there is less need for providing supplements. When you have to provide fewer supplements that means less cost for you the producer. Do you see the importance of taking care of the soil?
In order to improve pasture health, productivity, and longevity an effective first step must be taken. This is where doing a soil test comes in. However, this often gets put on the back burner as producers deal with the everyday tasks of caring for their land and livestock. Here are 5 tips to get the most return from your soil test.
Tip #1: Establish your soil test parameters
The first step in doing any kind of test is to set what it is that you are looking for. Once you have decided that you can then choose what lab you are going to be using. You will want to identify a certified soil testing laboratory that does the kind of test that you are looking for. There should be at least 1 in every state and is often on the campus of your local land grant college. Here in Texas that would be the Soil Testing Lab with the Texas A&M AgriLife Extension Service.
There are many different types of tests that you can go with depending on what you are looking for and the price. If the primary goal is to use this test to make fertilizer decisions then soil pH, organic matter, phosphorus, and potassium will be critical. If you have some carbon or microbial activity goals then there are other tests to go with.
Finally, you will want to establish the depth that you will be taking the core samples from. Doing this will ensure a more uniform sampling. It may also be useful to let the lab that you are going with know what this is as well. Your core depths, whether 6 inches or 2-3 inches should be selected based on measure decisions.
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 pretty 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 the desired level. This test is needed 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 is usually requested for environmental or research purposes.
Tip#2: Make an action plan
The investment of doing a soil test will do you no good if you do not follow through. You should consider how the soil test results will be utilized to make your management decisions. Make sure that the timing will be right when you improve the soil performance.
Depending on the topography you may not need to collect samples from the whole pasture. Consider taking samples based on similar management zones, or paddocks. If the area will be inaccessible to fertilize then do not take a sample from there.
Another area to avoid is within 150 feet of limestone roads. The road dust may influence the soil. Also avoid areas of cattle concentration like feeding areas, near water troughs, or loafing areas. The higher levels of manure and urine can affect the test results.
Tip# 3: Do the soil test right
How you take the samples can be just as important as what you take. Performing the steps correctly can reduce the negative influence on your test. Following the same steps for every sampling will mean a more uniform result.
You should start with clean sampling materials. You do not want previous samplings to influence your results. Discard and re-sample a core if it looks or feels significantly different from the other cores in that area. Walking in a random zigzag pattern takes 10-15 cores to get a good overall sampling of your pasture.
After you remove the grass tuft from the top put all of the cores in a plastic bucket. Thoroughly mix the together and then use the mixed cores to fill the soil sample bag. After each sampling, you will need to clean the bucket out to prevent cross-contamination. If you are interested in learning more about how to take a good soil test then check out my previous post “Don’t hold back your soil test”.
Tip#4: Move the limiting nutrients to the front of the line
With the current high input prices, it may not be economical to address all of the nutrient shortfalls in one year. Assess the limiting nutrients and prioritize which nutrient applications will give you the most return. Once you take care of the most important then you can move down the list as needed.
The first thing that you will need to address is soil pH. For grass-based pastures, the pH range you need is 6.0-7.0 A legume-mixed pasture will require a minimum pH of 6.5. Legumes have the best response to improved pH so lime applications are necessary to increase their production.
The results will also tell you how much Nitrogen, Phosphorus, and Potassium to apply. Nitrogen is often the first nutrient that is applied because of the obvious yield response. However, Inadequate levels of Phosphorus and Potassium can limit yield boosts. Correcting P and K from low levels to the optimum level can improve pasture yield by 65-80%. Getting the potassium level right is also a good idea if you will be planting any new forages to help with root development.
Tip#5: Keep at it
Like many other management practices used to improve a pasture doing a soil test is not a “one and done”. Things like rainfall, grazing, and other environmental conditions can affect soil nutrient levels. Ideally, you should sample each pasture every 3-5 years to monitor any changes in soil fertility.
