AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Summer 2003, No. 4
The only way to assess soil fertility is by sampling and testing soils. So the first step in evaluating your management practices is to adopt a regular soil testing program.
Keeping good records is important for finding trends. Dig out at the very minimum the last three years of soil tests that were taken on a field or field area. Put them in order from earliest to latest. Have soil tests been increasing, decreasing, or staying about the same?
To understand what you see, review records of management and weather. If samples were taken at different times of the year, under very different moisture and/or temperature conditions, or at different depths, results may not make much sense. Changes in tillage practices can also make a difference.
If you discover that there has not been good quality control in sample collection, don’t despair. The time to start assuring better quality is now. Make sure that you not only collect representative samples, but send them to a quality lab.
You may also discover that your management records are too sketchy to be of much help. Again, if this is the case, don’t fret. Now that you know how important these records are, they can receive higher priority this year.
• If you started with high soil tests, you probably relied on the phosphorus and potassium already present in the soil to meet most of the crop needs. With applications much below crop removal rates, soil tests would be expected to decline. If you planned to maintain high soil test levels where phosphorus and potassium do not limit yields, you probably applied phosphorus and potassium at rates similar to crop removal.
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