Phosphorus and zinc interaction critical with starter fertilizer
Including starter fertilizer with any fertility program can play a big role in getting corn off to a vigorous start, but a key component to maximizing starter fertilizer applications involves managing the interplay between phosphorus (P) and zinc (Zn).
This P and Zn relationship is all the more important in 2013. There is strong evidence that farmers might be relying more on starter fertilizer due to the increase in cash-rent prices brought about by higher commodity prices and a move toward one-year renewals on their leases. Rather than apply a lot of fertilizer in the fall, farmers will rely on starter fertilizer in the spring in the hope that “their” crop will benefit from the nutrients in 2013, versus having the nutrients carry over to benefit another farmer who might bid them out on the ground the following year.
“Even short-term nutrient deficiencies – especially early in the growing season – can result in significant yield reductions,” says Barney Gordon, Ph.D., agronomic consultant and Professor Emeritus at Kansas State University. “One often-overlooked factor is the interaction between phosphorus and zinc. For corn to optimally use applied phosphorus, zinc levels must be adequate and available.”
Gordon notes that Zn is important to the synthesis of tryptophan, an important component of proteins and an essential compound needed for the production of growth hormones. “High phosphorus availability can induce zinc deficiency in soils that are marginally zinc deficient,” he said. “With zinc-deficient plants, cellular regulation of phosphorus is impaired and can result in absorption and translocation of toxic levels of phosphorus by plants and create symptoms resembling zinc deficiency.”
Gordon cautions growers that as much as 75 to 95 percent of applied P can get fixed in the soil, making it unavailable for plant uptake. He recommends the addition of Avail Phosphorus Fertilizer Enhancer to starter fertilizer to increase P availability and avoid this major yield-limiting factor.
Avail is a water-soluble additive for dry or liquid phosphorus fertilizer that acts as a shield to protect fertilizer from elements such as aluminum, iron, calcium and magnesium that would normally tie-up P fertilizer and render much of the nutrient unavailable to plants.
According to the 2010 International Plant Nutrition Institute’s study of soil test levels, most North American soils have critically low Zn nutrient levels. Adequate, available Zn is necessary to crops to effectively use applied P, Gordon says. “Many studies in corn have shown high soil phosphorus availability can induce zinc deficiencies when zinc is low,” the researcher adds. “In high phosphorus environments, isotope studies have shown that zinc may concentrate at the root surface but does not move into the plant. In high phosphorus environments with high phosphorus availability, negative interactions of phosphorus with metallic micronutrients should be anticipated.”
Gordon says steps should be taken to ensure micronutrient availability is adequate, such as applying Zn in starter fertilizer placed close to the row or with the seed.
In addition to P and Zn, nitrogen (N) also has an important role in fertilizer efficiency and potential yield. Gordon says up to 50 percent of applied N fertilizer can be lost to the naturally-occurring processes of leaching, volatilization and denitrification. Effective uptake of N is crucial due to its importance in building amino acids for plant growth.
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