Variable Rate Fertilizer Calculator

Application map from soil test zones and yield goals.

Zone size (acres)

Yield goal (bu/acre)

Soil test P (ppm)

Soil test K (ppm)

Organic matter (%)

N factor (lbs N/bu)

P₂O₅ removal (lbs/bu)

K₂O removal (lbs/bu)

Previous crop N credit (lbs/acre)

Manure N credit (lbs/acre)

P sufficiency target (ppm)

K sufficiency target (ppm)

Tab to move between fields

N rate (lbs/acre)

190

P₂O₅ rate (lbs/acre)

K₂O rate (lbs/acre)

104

Total N credits (lbs/acre)30

OM N credit (lbs/acre)30

P₂O₅ maintenance (lbs/acre)74

P₂O₅ buildup (lbs/acre/yr)23

K₂O maintenance (lbs/acre)54

K₂O buildup (lbs/acre/yr)50

P sufficient? (1=yes)0

K sufficient? (1=yes)0

Est. cost per acre ($)$214.03

Total zone cost ($)$8,561

How to Use This Calculator

Enter Zone Size (acres) and Yield Goal (bu/acre) for the management zone being calculated.
Enter Soil Test P (ppm), Soil Test K (ppm), and Soil OM (%) from lab results.
Set N Factor (lbs N/bu), P₂O₅ Removal (lbs/bu), and K₂O Removal (lbs/bu) for your crop.
Enter Previous Crop N Credit and Manure N Credit if applicable to reduce synthetic N rates.
Review Recommended N, P₂O₅, and K₂O rates (lbs/acre) — export these values to your precision ag controller for zone-specific application.

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