This spring, many factors should be considered to maximize applied phosphorus (P) fertilizer efficiency. One often-overlooked factor is the interaction between P and zinc (Zn). Adequate, available Zn is necessary for crops to optimally use applied P.

North American soils have critically low (or below) Zn nutrient levels – as proven in the 2010 International Plant Nutrition Institute’s (IPNI) study of soil test levels in North America. Knowing of these deficiencies makes balancing soil nutrients a top-concern for growers. The IPNI 2010 research includes 4.4 million samples and 63 laboratories across all regions. Of those samples 37 percent showed less than 1 ppm Zn and 16 percent less than 0.5 ppm Zn.

“These regional trends are quite apparent,” says Paul Fixen, Ph.D., IPNI’s senior vice president and director of research. “Look at the upper Northern Great Plains area; this is the lowest phosphorus region in North America.”

Crops need zinc?

Yes. Don’t forget the Zn. Micronutrients, including Zn, are essential for overall plant

health and optimum yield.

Many studies in corn and dry beans have shown high soil P availability can induce Zn deficiencies when Zn soil test is low. Research indicates P effects on depressing Zn uptake are physiological in nature and are not due to Zn inactivation or fixation in the soil. In high P environments, isotope studies also have shown Zn may concentrate at the root surface but does not move into the plant. In high-yield environments with high P availability, negative interactions of P with metallic micronutrients should be anticipated; steps should be taken to ensure micronutrient availability is adequate (e.g. Zn in starter fertilizer placed close to the row or with the seed). 1, 2

Protect nutrients against fertility challenges

Researchers estimate as much as 75 to 95 percent of applied P fertilizer becomes fixed in the soil, making it unavailable for plant use3. Despite these challenges, growers still are expected to produce prosperous crops.

To do so, nutrients must be applied at optimal levels to avoid deficiency, while maintaining manageable input costs. Even short-term deficiencies, especially early in the growing season, can result in significant yield reductions. Retailers, crop consultants and growers alike should know the importance of nutrient management, how each element affects the bottom line and the available tools to help protect P fertilizer investments. To help ensure adequate P availability and uptake, many growers throughout North America use SFP’s AVAIL® Phosphorus Fertilizer Enhancer with their P fertilizer applications.

“Modern agricultural innovations continue to give growers the ability to produce high yields while maximizing resources and nutrients,” says Barney Gordon, Ph.D., agronomic consultant and emeritus professor in Kansas State University’s department of agronomy. “Despite weather variables, efficient nutrient use saves a crop. In bad years or good years, adequate essential elements, if made available, will help the grower stay ahead.”