Six Important Questions Farmers Should Ask Themselves Regarding Phosphorous Management

February 01, 2022


Phosphorus is one of the most common substances found in nature. It is an essential element for plant growth and is necessary to maintain a profitable yield. With countless crucial roles in a plant, it is one of the most important macronutrients to ensure a successful harvest. Phosphorous provides improved root development, resistance to disease and can boost early plant growth. 

Phosphorous can act like micronutrients in soil making it difficult to extract. When analyzing phosphorus nutrient application, orthophosphate is the only major form of phosphorous that can be taken up by the plant. Phosphorous easily bonds with other nutrients in the soil and becomes unavailable for plant uptake. Plants are not able to easily break this bond and rely heavily on soil microbes, mainly fungal species, to free the phosphorus. An insufficient supply of phosphorous can have an adverse effect on crop growth and yield. That’s why it’s so important for farmers to manage their crop’s phosphorous levels throughout the growing season. 

How to tell if my plant is deficient in phosphorus? A phosphate-deficient plant will show varying symptoms depending on the type of the plant. Corn, for example, shows its deficiency on the exterior of the leaf with a dark purple hue and by stunted growth. Checking for phosphorous deficiency signs and managing phosphorous levels both pre-and post-emergent are keys to a successful yield. 

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What's the right pH level in phosphorus? Look for a pH lower than 7.2 (calcium bonds above 7.2) and higher than 6.3 (iron and aluminum bonds below 6.3).

When and how should I apply phosphorus? Phosphorus is best applied in spring, prior to planting by a granular application of MAP or DAP. Liquid products, in-furrow and 2x2 applications can supply the plant with concentrated bands of phosphorus to replace some of the demand for dry fertilizer. Foliar applications also create a good source of available phosphorus and during peak demands has an even greater efficiency. According to research conducted by Dr. Carl Spiva, a pound of foliar phosphorus is equivalent to 20 pounds of soil applied fertilizer.1 

Why should I choose an orthophosphate over a polyphosphate starter product? Orthophosphate is readily available to a plant, meaning it can be taken up anytime. On the other hand, polyphosphate products need to undergo enzyme-driven hydrolysis, which generally occurs at or above 50-degree soil temperature for conversion (between 10 to 14 days) to orthophosphate. 

Should I consider stimulating soil microbes to promote the release of phosphorus? Vitalyze™ fertilizer contains 15 labeled microbes that boost mineralization of the soil, creating more readily available nutrients.Your Simplot Grower Solutions sales representative can make suggestions that fit the needs of your fields. 

When looking at premium phosphorus starter fertilizers, what makes each product different than the other? Each starter fertilizer contains a different blend of orthophosphate to polyphosphate, chelators and micronutrients. A starter fertilizer like Captivate™ EDTA contains orthophosphate and has an innovative technology called V-row which helps keep the orthophosphate available for plant uptake. It’s essential to find starter fertilizers that provide readily available phosphorous and increase early season growth to maximize your yield potential. 

1 Midwest Laboratories. (n.d.). Agronomy Handbook. Retrieved from 

- Tyler Carda 

Tyler worked as an intern with Pinnacle Agriculture for 3 years, which gave him the opportunity to work directly with Innvictis Crop Care, LLC and Mission Seed Solutions, LLC products in both full fields and strip-trial settings. This experience allowed him to fully understand how proprietary products perform in different scenarios. Tyler is now a Simplot Grower Solutions Proprietary Products Agronomist for the northern geographies. He has a Bachelor’s degree in Agronomy and Precision Agriculture from South Dakota State University. 

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