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

Fall 1996, No. 5


Seeing is believing. Have you ever heard that adage? Most of us have. It applies to many things...including deficiencies of plant nutrients such as phosphorus and potassium. So once we can see actual symptoms of nutrient deficiency on our 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 the wrong approach. Once a symptom appears, it is too late. Some yield and perhaps quality have already been lost.

Plants initially do not show obvious symptoms of nutrient deficiency other than slower growth which can be due to many factors. And, in the case of a mild deficiency, they may never show a visual symptom. 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. This leads to less yield, harvesting difficulties and lower quality of the harvested product. And as previously stated, this can all occur without diagnostic symptoms appearing.

Another problem is that not all deficiencies produce clear cut 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 then the secondary one will manifest itself. All the time the crop is losing yield.

True...a nutrient deficiency can be corrected within the growing season. And growth will resume at a maximum rate under optimum conditions. But the plant frequently has lost some percentage of its 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 use in preventing 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 be more appropriate: 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.

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