Wheat Producers Should Keep
Phosphorus Prices in Perspective
MANHATTAN, Kan. – Phosphorus (P) fertilizer prices are high, no question, but wheat producers should not overreact to the lofty price tags by cutting back on phosphate fertilizer if it’s needed for the wheat crop, said Kansas State University agronomist Barney Gordon.
”Where soil phosphorous levels are low (10-20 parts per million Mehlich III or Bray-1 P) or very low (less than 10 ppm), the likelihood of a wheat yield response to phosphorous is greater than 50 percent,” said Gordon, who is the agronomist-in-charge at the K-State Research and Extension North Central Experiment Field near Belleville. “And often, the yield response is great enough to more than pay for the phosphorous fertilizer, even at today’s prices.”
In mid-August, prices in Kansas for dry and liquid forms of phosphorus ranged from $1.00 to $1.30 per pound—approximately 180 to 210 percent higher than a year ago.
Wheat tends to be highly responsive to P input if the soil test category is low or very low, he said. Phosphorus is generally the second-most limiting nutrient in wheat production behind nitrogen, but in some areas of the Great Plains, phosphorous is even more limiting than nitrogen.
“Early-season phosphorous deficiency can limit wheat yield potential. The first five to six weeks after emergence is the critical period. Wheat absorbs about 18 percent of its total phosphorus seasonal uptake in just the first two weeks of growth,” Gordon said.
Phosphorus has major impacts on tillering and rooting of wheat, and an early-season P deficiency can reduce these important aspects of growth and development, he explained. A poorly developed plant is more susceptible to stresses in winter and spring.
“It doesn’t take much added phosphorous fertilizer, with the proper timing and placement, to have a big effect on early-season development and yields,” the agronomist said.
Later-season phosphorous deficiency has a much lower impact on wheat production than early-season phosphorous deficiency.
Gordon said the biggest response to phosphorous will come from placing the fertilizer with the seed, either as a dry product such as 11-52-0 or a liquid such as 10-34-0. Broadcasting P can also improve early-season wheat growth in some cases (especially on soil testing medium for Mehlich III or Bray-1 P), but broadcasting is less efficient and requires a higher rate to obtain a similar response, making it more expensive.
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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.
Story by: Steve Watson
swatson@ksu.eduK-State Research & Extension News Barney Gordon is at 785-335-2836 or bgordon@ksu.edu.