two people sampling the soil

Utilizing Soil Test Results

August 30, 2022 7:30 a.m.

With phosphorus being critical throughout a plant’s entire life cycle it’s important we understand how phosphorus’s availability is influenced by our soil.  Soil phosphorus consists of two forms: organic (non-plant available) and inorganic (plant available) P. While these forms exist in equilibrium and replenish each other, the process is very slow, so the amount of available P can be relatively low. To add to the complexity, the inorganic, or plant available form of P, is highly reactive and can be tied up by our soils. Therefore, you’ll often hear the term P-solution used to describe the amount of inorganic P actually available to the plant. You may have heard the phrase “Plants don’t chew, they drink”, well this is exactly right as the inorganic P has to be dissolved into solution (P-solution) for the plant to be able to take it in. One of the problems we face when applying phosphorous fertilizers is its reactivity with our soils, as the majority of the P we apply will either adsorb to the soil or precipitate out of solution, both making it unavailable to our crops.

Utilizing soil test results is the best way to understand soil pH, organic matter, CEC and available nutrient levels to inform fertilizer management decisions.

Because it takes about nine pounds of phosphorus to raise a soil test one unit, there can be concern about the amount of unused phosphorus left in the soil and loss to the environment. Though phosphorus is immobile in the soil, physical movement through runoff or leaching can happen once soils reach their phosphorus saturation point. Runoff is a major cause of phosphorus loss for growers. The water carries away the soil-bound phosphorus, and dissolved phosphorus from manure and fertilizers. Leaching also removes dissolved phosphorus from the soil through vertical water movement. It can be a concern when there is a high level of phosphorus in soils where connections to tile drains exist.

That’s why retailers and growers have a responsibility to help properly manage fertilizers in crops that provide economic, social and environmental benefits. Using the 4R nutrients stewardship concept is an easy way to ensure that the right fertilizer source at the right rate at the right time and in the right place, to keep a grower’s operation thriving.

For help with your nutrient management plan or for more information about Trivar, contact your CHS Agronomy representative or visit