Fertilizer Mixing Calculator
Calculate custom N-P-K dry fertilizer blend weights (lbs/acre and total field tonnage) for Urea 46-0-0, DAP 18-46-0, and Potash 0-0-60.
Calculate Custom Dry Fertilizer Blend
Enter target Nitrogen (N), Phosphate (Pâ‚‚Oâ‚…), and Potash (Kâ‚‚O) requirements and field acreage.
Calculation Results
Calculated using commercial fertilizer blending algorithms: \text{Total Blend} = \text{DAP Rate} + \text{Urea Rate} + \text{Potash Rate}
Quick Summary
The Fertilizer Mixing Calculator evaluates custom bulk dry blending ratios ($\text{Total Blend} = \text{Urea} + \text{DAP} + \text{Potash}$) for Urea 46-0-0, DAP 18-46-0, and Potash 0-0-60 to meet exact soil test recommendations.
Formula Explanation
\text{DAP Weight (lbs/acre)} = \frac{\text{Target P}_2\text{O}_5}{0.46}
\text{N from DAP (lbs N/acre)} = \text{DAP Weight} \times 0.18
\text{Urea Weight (lbs/acre)} = \frac{\text{Target N} - \text{N from DAP}}{0.46}
\text{Potash Weight (lbs/acre)} = \frac{\text{Target K}_2\text{O}}{0.60}How It Works
Commercial ag retail dealers blend single-nutrient materials (Urea, DAP, Potash) in bulk vertical batch mixers. The Fertilizer Mixing Calculator computes the exact pounds per acre of each ingredient required, accounting for multi-nutrient interactions (such as N contained in DAP) to deliver a perfectly balanced custom N-P-K prescription.
Step-by-Step Worked Example
Practical Problem: Soil recommendation calls for 150 lbs N, 60 lbs Pâ‚‚Oâ‚…, and 90 lbs Kâ‚‚O per acre on 100 acres using Urea (46-0-0), DAP (18-46-0), and Potash (0-0-60). Calculate required blend weights.
- Step 1: DAP required for 60 lbs Pâ‚‚Oâ‚…: $60 / 0.46 = \mathbf{130.43\text{ lbs DAP/acre}}$.
- Step 2: Nitrogen supplied by DAP: $130.43 \times 0.18 = \mathbf{23.48\text{ lbs N/acre}}$.
- Step 3: Remaining N required from Urea: $150 - 23.48 = \mathbf{126.52\text{ lbs N/acre}}$.
- Step 4: Urea required: $126.52 / 0.46 = \mathbf{275.04\text{ lbs Urea/acre}}$. Potash required $= 90 / 0.60 = \mathbf{150.00\text{ lbs Potash/acre}}$.
- Step 5: Total custom blend weight per acre: $130.43 + 275.04 + 150.00 = \mathbf{555.47\text{ lbs/acre}}$ ($27.77\text{ total tons for 100 ac}$; grade 27-11-16).
Real-World Calculation Examples
Scenario 1: High Corn Prescription (150-60-90)
Parameters: 150 N, 60 Pâ‚‚Oâ‚…, 90 Kâ‚‚O target
Result: 555 lbs/acre blend (275 lbs Urea, 130 lbs DAP, 150 lbs Potash).
Scenario 2: Soybean Prescription (0-50-120)
Parameters: 0 N, 50 Pâ‚‚Oâ‚…, 120 Kâ‚‚O target
Result: 309 lbs/acre blend (0 lbs Urea, 109 lbs DAP/TSP, 200 lbs Potash).
Scenario 3: Wheat Prescription (100-40-40)
Parameters: 100 N, 40 Pâ‚‚Oâ‚…, 40 Kâ‚‚O target
Result: 348 lbs/acre blend (183 lbs Urea, 87 lbs DAP, 67 lbs Potash).
Scenario 4: High Nitrogen Topdress (180-0-0)
Parameters: 180 N, 0 Pâ‚‚Oâ‚…, 0 Kâ‚‚O target
Result: 391 lbs/acre blend (391 lbs Urea, 0 lbs DAP, 0 lbs Potash).
Key Benefits of Using This Calculator
Multi-Nutrient Credit Accounting
Automatically deducts secondary Nitrogen contained in DAP (18-46-0) or MAP (11-52-0) from total Urea requirements.
Ag Retailer Batch Sheet
Generates exact ingredient weights per acre and total field batch tonnage for ag retail dry blenders.
Custom Blend Grade Output
Calculates equivalent custom fertilizer N-P-K grade ratio (e.g. 27-11-16) for custom mixes.
100% Free & Client-Side
Executes locally in your browser with zero latency or web server transmission.
Frequently Asked Questions (FAQ)
Why does DAP (18-46-0) affect Urea calculations?
DAP contains 18% Nitrogen by weight. When applying DAP to meet Phosphate goals, the Nitrogen in DAP satisfies part of the crop Nitrogen requirement, reducing needed Urea.
What is custom dry fertilizer blending?
Custom blending physically mixes straight materials (Urea, DAP/MAP, Potash) in specific weight ratios tailored to a field's exact soil test recommendation.
How do I calculate custom blend N-P-K grade ratio?
Grade N% = (Target N / Total Blend Weight) × 100; Grade P% = (Target P₂O₅ / Total Blend Weight) × 100; Grade K% = (Target K₂O / Total Blend Weight) × 100.
Can Urea and DAP be safely dry blended together?
Yes — dry Urea (46-0-0) and DAP (18-46-0) can be dry blended and spread immediately. Avoid long-term humid storage as atmospheric moisture can cause caking.
What if my soil test requires no Phosphorus (0 lbs Pâ‚‚Oâ‚…)?
If Pâ‚‚Oâ‚… target is zero, the calculator omits DAP and calculates straight Urea (46-0-0) and Potash (0-0-60).
Can I use MAP (11-52-0) instead of DAP (18-46-0)?
Yes — MAP provides 52% P₂O₅ and 11% N, requiring fewer bulk pounds per acre than DAP for the same Phosphate rate.
How does fertilizer particle size segregation happen in spreaders?
If blend ingredients have different particle sizes (SGN numbers), larger particles throw further from spinner disks, causing uneven field distribution.
What is SGN (Size Guide Number)?
SGN measures average granule diameter in millimeters × 100 (e.g. SGN 240 = 2.4 mm). Blending materials with similar SGN prevents segregation.
How do I add Micronutrients (Zinc, Sulfur) to a dry blend?
Add granular Zinc Sulfate (35% Zn) or Elemental Sulfur (90% S) to the batch mixer based on soil test micronutrient target rates.
Why is custom blending more economical than pre-packaged 10-10-10?
Custom blending uses high-analysis straight materials without inert fillers, lowering freight costs and applying only nutrients needed by soil.