AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Summer 1999, No. 2
WATCHING FOR NUTRIENT STRESS...ANY STRESS
Our crops are stressed all the time. This sounds like a drastic statement, but it is none-the-less true. If not, why are growers consistently producing low yields? Consider the following documented yields, each of which are several-fold greater than the national average:
These yields are impressive and suggest that we can grow crops at much higher levels than we are now. But even they were not produced under totally optimum conditions. Plant breeders tell us that the genetic potential is substantially higher yet. This is important…at least to our kids and grandkids…as world population expands.
• 370 bushels of corn per acre produced in Illinois in 1985
• 209 bushels of wheat per acre produced in Washington in 1965
• 5.4 bales of cotton per acre produced in Arizona in 1982
Crops can suffer many different stresses, each taking a bite out of ultimate yield…infestations of insects and weeds, disease problems, extremes in temperature—too hot or too cold, moisture fluctuations from drought to flooding, and others, including nutrient stress…usually from a deficiency of one or more plant essential nutrients.
Not all crop stress can be controlled. But where possible, our goal must be to eliminate or at least minimize stress whenever and wherever it occurs. Better yet, address the problem before it occurs. Less stress means more yield.
Nutrient deficiency is a controllable stress. After all, we have an array of quality fertilizer products at our fingertips; proper fertilizer management will eliminate this stress. Unfortunately, it is not quite as easy as it sounds because, first, we are not dealing with one stress, but potentially multiple stresses. There are 17 plant essential nutrients, 13 of which can become deficient. Of the other four, carbon, hydrogen and oxygen come from air and water, and nickel has never been found deficient in normal cropping situations. Second, nutrient deficiencies are not always obvious. It is not like a weed problem. Either the weeds are there or they are not. Considerable yield can be lost in some cases with little or no deficiency symptoms appearing on the plant.
Steps to prevent nutrient deficiencies takes several forms:
Are we doing our best to minimize stress? The high yield levels reported above suggest that we are not. Why? Because the most recent high yield occurred in 1985…14 years ago. Where are the high yields of the 1990s? The potential is there…in the seed we plant. Let’s redouble our efforts to minimize stress. Proper fertilization eliminates nutrient stress. That along with other stress relievers will produce the high yields necessary to sustain us in the new millenium.
1. History of the field and general area: Past experience is always helpful, that of the grower as well as that of a neighbor.
2. Preplant soil analysis: Tests, not for just one year, but on a regular basis will document available levels and trends over the years.
3. In-season plant analysis: Samples taken during maximum nutrient demand can identify unsuspected stress.
4. Visual symptoms: In-season observations of plant vigor and any growth or color abnormalities can suggest problems. However, as already observed, this information may be too little, too late.
5. Crop demand: Understanding the particular nutrient requirements of a crop can suggest the likelihood of certain nutrient deficiencies.
For more information, contact Dr. Albert E. Ludwick, Western Director, PPI, P.O. Box 970, Bodega Bay, CA 94923. Phone: (707) 875-2163. E-mail: email@example.com.
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