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

Winter 2003, No. 6

FALL-APPLIED PHOSPHORUS.WILL IT BE THERE IN THE SPRING?

Many fields in North America could benefit from phosphorus fertilization: 47% of the soil samples test medium or below in extractable phosphorus. Is fall a good time to apply phosphorus, and will the applied phosphorus be available for spring planted crops?
Where phosphorus has been applied at agronomic rates, it moves very little (less than an inch or two)from the depth of placement or tillage in most soils within 5 to 10 years or more. It is unusual for any significant phosphorus leaching to occur unless excessive rates of phosphorus from animal wastes or other sources have been applied and the phosphorus sorption capacity of the surface soil has been saturated.

Plants may absorb 10 to 30% of the applied fertilizer phosphorus within the year of application. When the soil pH is maintained at proper agronomic levels for most crops (6.0 to 6.5), much of the applied phosphorus remains in forms that plants can utilize. It may take several years to “recover” the applied phosphorus, but many research studies have shown that the apparent plant recovery of fertilizer phosphorus by long-term cropping may range from 40 to 100%.

So, fall-applied phosphorus can benefit fall crops as well as spring crops, and it will provide benefits to successive crops. The benefits depend on several factors…including the balance of phosphorus applied versus phosphorus removed in the harvested crop…and the ability to keep phosphorus in the field where it is applied for maximum plant nutrition. Evaluate the advantages of fall-applied phosphorus and be sure to include it as a viable option in your nutrient management plan.
—CSS—

For more information, contact Dr. Cliff S. Snyder, Midsouth Director, PPI, P.O. Drawer 2440, Conway, AR 72033-2440. Phone: (501) 336-8110. E-mail: csnyder@ppi-far.org

A-B Winter 03-04 #6.pdf
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