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Soil Fertility: Put It All Together

Posted Jun. 1, 2006

No, I'm not talking about applying Triple 13 or any other fertilizer blend. I've assembled six steps from start to finish that I think are essential for any soil fertility program.

  1. 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. 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."
  2. Label the sample appropriately.
    The labeling affects all of the following steps. The minimum required information is your name and contact information (so the results can be sent, and so you can be contacted if there are questions about the sample), 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.
  3. Have the sample analyzed by a reliable laboratory.
    At the Noble Research Institute, we continually monitor the lab we use for precision and accuracy. Most labs, including the one we use and most university labs, participate in the North American Proficiency Testing program. In this program, samples of known analysis are run blindly by labs to check their performance.
  4. Interpret results and make recommendations.
    This is the job of your agronomist, i.e., Noble Research Institute soil and crops specialist, county Extension agent, etc. We 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, we 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.
  5. Follow the recommendation.
    You went through the trouble of taking a soil sample for a reason. If we all did a good job on steps one through four, then why would you not follow the recommendation? Well, there are some reasons. 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. Some ways of making changes may be more beneficial or less detrimental than others.
  6. 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, you can monitor response to fertility 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.

Now we've come full circle. With the current high price of fertilizer and expected higher price in the future, you owe it to yourself to put it all together.