AGRI-BRIEFS
  AGRONOMIC NEWS ITEMS 		From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335

Fall 1997, No. 2

FERTILIZE BEFORE NUTRIENT DEFICIENCY OCCURS, NOT AFTERWARD

Seeing is believing. Have you ever heard that adage? Most of us have. It applies to a lot of things...including deficiencies of plant nutrients such as phosphorus and potassium. So once we can see actual symptoms of nutrient deficiency on a crop it is time to apply fertilizer. Right? After all, this approach eliminates the possibility of applying fertilizer where it might not be needed. No...this is absolutely the wrong approach. Once a symptom appears, it is too late. At least some yield --- perhaps a lot --- and quality have already been lost.

Management of fertilizers is a little different than that for pesticides. The results of a fertilizer application are less obvious unless we actually leave check strips to compare growth differences. Otherwise, the entire field might appear normal. In contrast, an application of an insecticide brings obvious results...results that can be seen quickly. The same is true for contact herbicides. The sight of dying and dead weeds tells a satisfying story.

Plants initially do not show obvious symptoms of nutrient deficiency other than slower growth which may be due to many factors. And, in the case of a mild deficiency, they may never show a symptom that is diagnostic. A nutrient deficiency causes a disruption in any number of essential metabolic processes within the plant which causes growth to slow and to eventually cease in severe cases. Crops mature unevenly because deficiencies rarely occur uniformly across entire fields. The results are less yield, harvesting difficulties and lower quality of the harvested product. And as previously stated, this can all occur without the appearance of diagnostic symptoms.

Another problem is that not all crops produce clear cut deficiency symptoms. Or for a particular nutrient, one crop may do so and another not. Then there is the possibility of multiple deficiencies. The most severe will likely be manifested. Once that deficiency is corrected through fertilization, the secondary one will manifest itself. Meanwhile, the crop is losing yield.

A nutrient deficiency can sometimes be corrected within the growing season. And growth will resume at a maximum rate under optimum conditions. But the plant frequently has lost some yield potential that will not be regained. This is especially true in weather-limited growing seasons.

So, what to do? Correct potential nutrient deficiencies before they occur. Use your management experience, field history, and very importantly, routine soil and tissue testing to give you the predictive information to prevent nutrient deficiencies in the first place and to optimize growth for maximum profits.

Seeing is believing. But in the case of nutrient deficiencies, seeing is too late. Another adage might best apply: A day late and a dollar short. Don't wait until you see deficiencies before fertilizing because you will indeed be a day late and a dollar short...and a lot more.


--- AEL ---

For more information, contact Dr. Albert E. Ludwick, Western Director, PPI, P.O. Box 1326, Bodega Bay, CA 94923. Phone (707) 875-2163. E-mail: aludwick@ppi-far.com.
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