Okla. -- A complete and successful soil fertility program involves six steps, according to Noble Foundation soil and crops specialist Jim Johnson. With the current high price of fertilizer and expected higher price in the future, following these steps could be a money-saving move for agricultural producers.
Take a good soil sample.
Take a minimum of 15 cores per field to a depth of 6 inches. The 6-inch depth is important because calibrations are based on this depth.
"Do not sample places you know do not represent the majority of the field, such as areas near gates, water, feeders, bad spots, etc.," Johnson says.
Mix the cores well in a clean plastic container, and send one pint of soil for testing. For more information on soil sampling, call (580) 224-6500 and ask for the Noble video "Unless You Test, It's Just a Guess."
Label the sample appropriately.
The labeling affects all of the following steps. The minimum required information is name and contact information, the intended crop, the yield goal, if the crop is already established or not (all of these affect the recommendation, and the intended crop can even affect the tests that are run on the soil) and the field name or number.
Have the sample analyzed by a reliable laboratory.
"At the Noble Foundation, we continually monitor the lab we use for precision and accuracy," Johnson says.
Most labs, including the one used by Noble and most university labs, participate in the North American Proficiency Testing program. In this program, labs run samples of known analysis blindly to check their performance.
Interpret results and make recommendations.
"This is the job of your agronomist, i.e., Noble Foundation soil and crops specialist, county Extension agent, etc., Johnson says.
When interpreting results and making recommendations, agronomists start by using calibration research done by the state university to determine the likelihood of an economic response to a given amount of fertilizer on a soil with a given soil test index. Then, they use specific information about yield goal, value of the crop, price of fertilizer and application timing and environment, among other things, to make specific fertilizer recommendations.
"So, obviously, the more the person making the recommendation knows about your operation and your fields, the better recommendation he or she can make," Johnson adds.
Follow the recommendation.
"You went through the trouble of taking a soil sample for a reason, Johnson says. "If we all did a good job on the first four steps, why would you not follow the recommendation?"
Well, there are some reasons, Johnson concedes. Price is usually the biggest one, and weather is number two.
"If you want to deviate from the recommendation, contact the person who made it," he says. "Some ways of making changes may be more beneficial or less detrimental than others."
Keep records to make adjustments.
At the very least, record the fertilizer applied and the yield in each field. Rainfall records are also good to keep. Then, response to fertility can be monitored in each field.
"That way, in the future, you can adjust fertilizer application to take advantage of fields that give you a better response and minimize application on fields that don't respond as well," Johnson says.
Jim Johnson is a soil and crop specialist in the Agricultural Division of the Noble Foundation.