With the lack of rainfall this year there is no question that yields goals were not meet with few exceptions. This makes soil sampling this fall extremely valuable. Determining what residual fertility remains in the soil can give you credits to carry over to the next crop year. Soil testing is the only way to accurately determine what residual fertility remains.

Soil testing is the foundation of a sound fertility management program. A soil test is a series of chemical analyses on soil which estimates whether levels of essential plant nutrients are sufficient to produce a desired crop and yield. When not taken up by a crop, some nutrients, particularly nitrogen, can be lost from the soil by leaching or volatilization. Others, like phosphorus, react with soil minerals over time to form compounds which 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. Care should be taken to prevent sampling across areas with historically different land uses, soil types, fertilization practices, or crop yields. A composite sample is obtained by combining 10 to 15 individual soil cores taken randomly across each field. The cores are placed in a clean plastic bucket, thoroughly mixed and then about 1 pint is sent 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 by 1-inch core from the center of the shovel slice. By collecting 10 to 15 individual cores across the area, one can better ensure that the soil test results will be representative of the site and fertilizer recommendations will be appropriate.

Complete sampling instructions and sample bags can be obtained from your local county Extension office and during the AgriLife Extension Soil Sampling Campaign, October 1 through November 15, crop and forage producers can have samples analyzed at a discounted rate and free shipping to the lab. There are three steps involved in obtaining a soil test through the soil sampling campaign: 1) obtain sample bags and instructions, 2) collect composite samples, 3) select the proper test, and complete the information sheet and return to the Nueces County Extension Office at 710 East Main Avenue, Suite 1 Robstown, Texas, 78380. For more information contact our office at 361-767-5223.

Individuals with disabilities, who require an auxiliary aid, service or accommodation in order to participate in any of the mentioned activities, are encouraged to contact the County Extension Office eight days before all programs for assistance. Extension programs serve people of all ages regardless of socioeconomic level, race, color, sex, religion, disability or national origin.