As much as 71 % of Texas remains in some stage of drought with long-range forecasts indicating potential for dry conditions to last another five or six years.
A soil test is essential to plan for nutrient management in pastures and fields intended for forage production, vegetable gardens or your front lawn. Just like the dipstick to check the oil in an automobile, a soil test checks to see what nutrients are present and which are needed to grow forages.
Soil testing is the only way to accurately determine what residual fertility remains and is the foundation of a sound fertility management program. When not taken up by a crop, some nutrients, particularly nitrogen, can be lost by leaching or volatilization. Others, like phosphorus, react with soil minerals over time to form compounds that are not available for uptake by plants. Soil testing can be used to estimate how much loss has occurred and predict which nutrient(s) and how much of that nutrient(s) should be added to produce a particular crop and yield.
Collecting a good soil sample is the most critical step in soil testing. It is generally recommended that one “composite” soil sample be collected from each uniform area (field or part of a field) of 10 to 40 acres. Take care to prevent sampling across areas with historically different land uses, soil types, fertilization practices, or crop yields. Combine 10 to 15 individual soil cores taken randomly across each field. Place the cores in a clean plastic bucket, thoroughly mix and send about 1 pint to the laboratory for testing.Individual soil cores can be taken using a regular spade, soil auger or soil sampling tube. First, scrape any plant residue from the surface and then make the core or boring 6 inches deep. Be careful not to remove dark colored, partially decomposed organic matter when removing plant residue. When using a spade, dig a 6-inch deep, 45-degree V-shaped hole and take a 1-inch slice from the smooth side of the hole. Then remove a 1-inch by 1-inch core from the center of the shovel slice. Collecting 10 to 15 individual cores across the area improves chances that the soil test results will be representative of the site and fertilizer recommendations will be appropriate
Nitrogen, phosphorus and potassium are needed in the largest quantities. Then there are some micro nutrients that also play vital roles in plant production.
With forage production, taking hay off removes nutrients and changes the soil environment every time you cut and bale.
For a one ton per acre forage production goal, coastal Bermuda grass needs approximately 50 pounds of nitrogen, 14 pounds of phosphorus and 42 pounds of potassium. For two tons, rates increase to 100, 28 and 84.
One ton production would need 8 pounds of calcium, 3 pounds of magnesium and 4 pounds of sulfur. The rate increases to 15, 6 and 8 for a two ton yield goal.
Nitrogen may be the most essential nutrient. Without nitrogen we get no growth. If nitrogen is deficient, grass will have a yellowish color. Ample nitrogen improves the grass’ ability to compete with weeds “and possibly decrease herbicide needs. Also, nitrogen increases forage production and crude protein.”
Nitrogen is mobile, leaches and volatizes.
Phosphorus, stimulates early growth and root formation, improves moisture and nutrient uptake and promotes optimum forage yield and quality. Phosphorus is immobile and will not leach or volatize. It is subject to stratification and may build up in the top 2 to 3 inches of soil where it us not readily available to the roots.”
Potassium aids water use efficiency, increases disease resistance and improves cold hardiness. It also does not leach is not volatile.
Potassium deficiency is uncommon in heavy soils and is more likely to occur in medium/coarse textured soils. Deficiencies may result in stand decline and winter kill.
A standard soil test only costs $10 per sample. Most of the time you will get the results back in about two weeks. In addition to knowing how much nitrogen, phosphorus and potassium is needed, you will also know the pH of the soil and soil salinity levels.
A quart size zip lock bag full of soil is all that is needed along with the required soil sample submission form and payment in order to send a soil sample in for testing at the Texas A&M Soils Lab in College Station, Texas. Soil test forms may be picked up from the Texas A&M AgriLife Extension Office in each county.
It is a simple process. Pick up the form and fill it out. Collect the soil sample. Mail/ship it to the lab along with the payment. Then wait for the results to be sent back to you.
So, spend $10 and learn exactly which nutrients are lacking and by how much, or keep guessing at which fertilizer blend to use and how much to apply. It has been said that knowledge is power. Money spent on a soil test should be a wise investment.
