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The Science Behind It: Phosphorus 101

“The Science Behind It” is an educational video series by Dr. Tuesday Simmons, science writer at Trace Genomics. It was created to illuminate the scientific foundations of soil microbiology that form the basis of Trace technology. This video is about the significance of phosphorus in agriculture and its role as a crucial macronutrient for plant growth.

More details on soil phosphorus can be found in our blog posts: “My phosphorus saturation is low – now what?” and “Bacteria as the Baristas of the Soil: Understanding the Phosphorus Cycle”.

Video Script:

Phosphorus is an element on the periodic table abbreviated as the letter “P”. For folks in the agriculture industry, it’s one-third of “NPK”, where the other 2 letters stand for Nitrogen (N) and Potassium (K). Together, N, P, and K are the three essential macronutrients that all plants need to grow. If any of these are low in the soil, crops may not grow to their full potential. This is why farmers will often apply fertilizers – the tricky part is knowing how much to add.

If growers add too much phosphorus fertilizer, excess can be leached away or lost through soil erosion, which isn’t good for their wallets or the environment. Understanding the phosphorus cycle can help growers and their agronomists make decisions about what type and how much fertility management products to use.

In the soil, phosphorus exists in 3 different states:

  • Organic forms that plants cannot use directly (like compost, crop residue, manure)
  • A soluble form that plants can use
  • Inorganic forms that plants cannot access (bound to iron, aluminum, or calcium in soil particles)

The second type, soluble, plant-available phosphorus, is only 6% of the total phosphorus in the soil. To make the best fertility management plan, Trace provides both chemical and biological data that impact the phosphorus cycle. This includes:

  • How much soluble phosphorus is in the soil (measured by Bray, Olsen, and Mehlich-3)
  • Second – Phosphorus saturation. This is a calculation that first measures the amount of inorganic phosphorus that your soil can hold (called the soil phosphorus storage capacity). You can think of that as the size of your phosphorus sponge. A larger storage capacity is like a larger sponge that can hold more phosphorus. Psat is a measurement of how full the storage capacity is, or how full your sponge is. This is a value from 0-100 where 100 is fully saturated with phosphorus.
  • The next two pieces of data are driven by soil biology, and we measure them using metagenomics. Phosphorus mineralization is a process by which microorganisms break down large organic phosphorus compounds, and when we sequence the DNA in the soil, we can find genes responsible for this process without having to identify the microorganisms first.
  • Similarly, phosphorus solubilization is when microorganisms transform inorganic phosphorus into soluble phosphorus that plants can use. At Trace, we can directly measure the potential for this activity using DNA.

All of this data together is organized into your TracePHOS report. We developed the TracePHOS report to deliver the most comprehensive analysis of your soil phosphorus. Importantly, rather than just overloading growers with a firehose of data, we also include interpretation – actionable insights that help to select the type of product that is most beneficial for your soil.

Plus, since we don’t expect everyone to have the phosphorus cycle memorized, each report includes the Science Behind It on the last page as a reference. By incorporating guidance from TracePHOS into a soil fertility management plan, growers can optimize retention of soluble phosphorus and prevent loss. This protects their valuable investment in soil nutrients and helps to maintain soil health for generations to come.

About the author: Dr. Tuesday Simmons is the Science Writer at Trace Genomics. She earned her Ph.D. in Microbiology from the University of California, Berkeley, studying the root microbiome of cereal crops.