Phosphorus (P) and potassium (K) uptake depend on diffusion, which is directly tied to soil moisture. When soils dry, nutrient movement slows, limiting what roots can access, even when nutrients are present in the soil.

Managing fertility to a single, uniform critical level ignores the sub-acre variability in moisture, landscape position, and soil properties that determine nutrient availability. As a result, some areas are under-supplied while others receive more fertilizer than they can efficiently use.

Why do we manage fertility the same across every acre when nutrient availability varies by environment?

How Environment Drives P and K Availability

By leveraging Advanced Agrilytics’ Soil Wetness Index (SWI) along with key soil attributes, we can map how soil moisture influences the diffusion of P and K across environments. Areas with lower soil moisture require higher critical levels— and therefore higher fertilizer concentrations—to overcome reduced diffusion. Areas with higher soil moisture require lower critical levels and lower concentrations due to greater diffusion potential. The resulting Delta-to-Critical analysis enables more efficient reallocation of fertilizer dollars while supporting positive agronomic outcomes.

Advanced Agrilytics Research Insights

Dry soils require higher nutrient concentrations. In water-limited areas, roots have less opportunity to uptake immobile nutrients like P and K.
Landscape position affects nutrient access. Topography influences mineralization, leaching, and runoff—altering how much P and K each environment (or zone) needs.
Soil characteristics matter. Texture, organic matter, and cation exchange capacity (CEC) all influence nutrient holding capacity and plant response.
Static critical levels miss the mark. What really matters is how much P and K the plant can access, not just what the soil test says is there. That’s why we use our proprietary Spatial Critical Levels that adjust by environment or zone.

What Growers Are Asking

“WHY AREN’T MY P AND K APPLICATIONS SHOWING UP IN SOIL TESTS OR YIELD?”

When moisture decreases, diffusion decreases which causes P and K uptake to decrease. It’s often not that you’re applying too little, it’s that you’re applying where the crop can’t access it.

“HOW DO I KNOW IF I’M APPLYING IN THE RIGHT PLACES?”

Our patented Spatial Critical
Levels, calculated by
TerraSIGNAL™, use topography, moisture, and soil properties to show where you’re above or below what the crop’s P and K
needs.

“DOESN’T THE SOIL TEST ALREADY TELL ME WHAT I NEED?”

Soil tests tell you what’s there, not whether it will be available when the crop needs it. Availability depends on pH, moisture, and how nutrients move (or don’t move) through the soil.

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Soil fertility is just one strategy in our proprietary spatial agronomy system, powered by TerraSIGNAL™.

Soil Moisture Drives Nutrient Uptake. Are You Managing for It?