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Timing Is Crucial For Young Seedlings
What Customers Want
TCGA Members Show Resilience
Strategies To Reduce Drift
Applied Phosphorus Adds More Scrutiny
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My Turn

Applied Phosphorus Adds More Scrutiny

By Dr. Barney Gordon
Grand Junction, Tenn.
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• Professor Emeritus, Kansas State University.
• B.S. in Agronomy, Mississippi State University.
• M.S. in Soil Chemistry, Auburn University.
• Ph.D. in Crop Physiology, Plant Nutrition, South Dakota State University.
• Area: Fertilizer efficiency and management in no-till production.
• Currently conducting cotton fertility research in West Tennessee.

You could say that my life and career have come full circle where cotton is concerned. I grew up in midtown Memphis, Tenn., – on Central Avenue – and attended Memphis University School. While working on my B.S. degree at Mississippi State University, I spent summers working at Delta Distributors in Hughes, Ark., and then joined that company as a full-time agronomist after graduation. My work focus at that time was insect scouting and weed control in cotton, and I logged some long, hot hours in the field. I also worked as a farm manager for a large cotton plantation in Crawfordsville, Ark., for five years.

When I went to Auburn University for a master’s degree, my research focus was nitrification inhibitors in cotton. I spent several years at Auburn as a research associate for my Ph.D. and then moved on to Kansas State University where I spent 22 years as a professor and researcher.

Today, I find myself back in West Tennessee conducting cotton research. I am living on a farm that has been in my family since the 1850s, and it’s great to be home again. I find cotton to be the most challenging crop to manage. It is a finicky plant – the interplay between disease and insects is like no other field crop, and proper fertility management is difficult to achieve because cotton fruits over such a long period of time. But once cotton gets into your blood, it’s pretty much there to stay.

Compared to nitrogen and potash, phosphorus (P) is trickier to manage effectively to ensure ample quantities of that nutrient are taken up by cotton. Just because soil tests may indicate adequate or high levels of phosphorus doesn’t necessarily mean that you are in good shape with that key nutrient. What matters most is how much of applied phosphorus is actually available for plant uptake.

The hard fact for P fertilizer is that between 75 and 95 percent of phosphorus often gets tied up or “fixed” in the soil. Within days or weeks after application, P undergoes a fierce chemical reaction in the soil that converts it from a soluble to an insoluble form, making it unavailable for plant uptake. The P that does get tied up in the soil may not revert to a soluble form until well after the cotton would need it. This is especially a concern in a no-till production environment. Due to a greater buildup of carbon and organic matter, the soil is much more active, and nutrient transformation is more enhanced.

For this reason, a farmer who applies 200 pounds of P in the fall might only realize a benefit from 10 to 50 pounds of the nutrient the following spring. In high-acid soils, P has a tendency to bind to iron and aluminum. In high-pH soils, phosphorus tends to bind to calcium and magnesium.

In no-till production, the surface residue, whether it is corn stalks, soybean or wheat stubble, cools the soil and prevents it from rapidly warming up. Plant roots grow slowly and are challenged to cover the soil volume necessary to absorb the nutrients and moisture they need for growth. In this type of situation, it is essential to have P in the root zone and available for crop uptake.

Fortunately, there is technology available to the farmer that reduces fixation of P in the soil and helps ensure the nutrient remains in the soluble form and can be readily used by crops via plant uptake. That technology is Avail Phosphorus Fertilizer Enhancer, and it can either be impregnated onto granular fertilizer or injected into liquid.

In three years of field research at two locations in West Tennessee, Avail from SFP increased phosphorus availability to 80 and 90 percent in cotton, which resulted in a 100-pound-per-acre lint yield increase.

These replicated tests – conducted at the Ames Plantation in conjunction with the Tennessee Farmers Co-op – involved applying Avail with phosphorus at rates of 30 and 60 pounds per acre.

High P availability can induce zinc deficiency in soils that are marginally zinc deficient. In high P environments, isotope studies have shown that zinc may concentrate at the root surface but does not move into the plant. Steps should be taken to ensure micronutrient availability is adequate, such as applying zinc in starter fertilizer placed close to the row or with the seed.

Contact Dr. Barney Gordon via email at or by telephone at (785) 243-0583.

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