Myron Sylling

Baseline Rx in action. Pretty cool to pull samples from zones across a field and still end up with consistency like this. We ask the soil what it can provide (before giving recommendations) by utilizing zones like these paired with soil analyses looking at its chemical, physical, and biological makeup.

If the goal is to build Phosphorus in the soil, it’s probably best to use a Bray P1, Mehlich 3, or an Olsen extraction and spread MAP and or DAP in the fall. Although some claim that these extractions tell us what’s “plant-available,” this is not totally true. Others claim that these extractions were created to help farmers determine if they should be applying phosphorus to maximize yield. Also not totally true. If we start by treating the soil as a math equation, we end up building phosphorus rather than supplying phosphorus to the crop. Here’s an example: 225 bu yield goal for corn 12.4 CEC soil in Central Indiana pH of 7.1 Bray P1 of 13 ppm Utilizing Purdue’s Tri-State Recommendations Fertilizer Tool, they are calling for 131 P2O5 or 252# of MAP. If @MasonClaude5 math is correct, then with soil moisture from 1 in of rain at 60° soil temps, we could solubilize up to 55% of applied phosphorus. In our scenario that would mean 138# of phosphorus could be solubilized in the fall. And that’s with one inch of rain. That equals tie ups come spring time. Especially if there is not enough WEOC in the system. This would essentially “build” phosphorus. Meaning the phosphorus is in an unavailable form. But that’s not really the goal. In the scenario from above, this sample had an H3A P of 18.4 ppm. Based on Agronomy 365’s recommendations, we would need 50# of P2O5 or 97# of MAP (applied in the spring). This sample also had a WEOC/CEC of 10 which is a good start. WEOC drives biology activity which helps drive phosphorus availability. When we rely on the soil to provide phosphorus and supplement where it needs help, we create efficiency. All of this to say, extraction methods matter. The reasoning behind extraction methods matters. These largely determine recommendations. A slight change in thinking about extractions and a slight change in how soils are viewed can make a huge difference to the plant/soil, but also make an economic difference.