Fertilizer Cost per Nutrient Unit: Compare N, P, K Prices

The tool divides the product price by the amount of nutrient it contains. The formula is: CostPerUnit = PricePerUnitMass ÷ NutrientMass, where NutrientMass = (NutrientPercent ÷ 100) × BaseMass. For example, if 1 short ton of fertilizer contains 920 lb of N (at 46%) and costs $500, the cost per lb of N is $500 ÷ 920 = $0.54/lb. The calculation converts the price unit to the display unit (lb or kg) and divides by nutrient mass. For products with zero percent of a nutrient, the cost is not calculated (shown as 'no N', 'no P₂O₅', or 'no K₂O'). Understanding this calculation helps you see how price and analysis determine cost per unit of each nutrient.

Fertilizer analysis is reported as N (elemental nitrogen), P₂O₅ (phosphorus pentoxide), and K₂O (potassium oxide). These are standard reporting forms by convention, not the actual chemicals in the bag. The first number (N) represents elemental nitrogen percentage by weight. The second number (P₂O₅) represents phosphorus expressed as phosphorus pentoxide—P₂O₅ contains about 44% elemental phosphorus (P₂O₅ × 0.44 = P). The third number (K₂O) represents potassium expressed as potassium oxide—K₂O contains about 83% elemental potassium (K₂O × 0.83 = K). This tool uses the oxide forms as labeled on fertilizer bags, which is the standard for comparing products and matching soil test recommendations. Understanding these labels helps you read fertilizer analysis correctly and calculate nutrient content accurately.

No. The tool only compares price per unit of nutrient. The cheapest source of a nutrient may not be the best choice for your situation. Consider factors like nutrient availability (some forms are more readily available to plants than others), soil pH (affects which nutrient forms work best), application method (liquid, dry, and gas forms have different equipment requirements), storage and handling (some products require special storage conditions), secondary nutrients and micronutrients (some products provide additional nutrients not captured in NPK analysis), and your specific crop needs (different crops have different nutrient requirements and timing). Always consult soil test results and local agronomic advice before making fertilizer decisions. Understanding tool limitations helps you use it appropriately as one input into comprehensive fertilizer planning.

No. The tool compares product prices only. It does not account for differences in nutrient availability (how readily nutrients are available to plants), uptake efficiency (how efficiently plants take up nutrients), timing (when nutrients are applied affects availability), losses to the environment (volatilization, leaching, runoff), or crop response (how crops respond to different nutrient forms). Some nutrient forms are more readily available to plants than others—for example, nitrate nitrogen is immediately available while organic nitrogen must be mineralized first. Some forms are more prone to losses—urea can volatilize if not incorporated, while ammonium forms are less prone to leaching. This simple price comparison does not capture these important differences. Understanding efficiency limitations helps you see why cost per unit is one factor among many in fertilizer decisions.

Application costs vary widely based on product form (dry, liquid, gas), equipment (spreaders, sprayers, injection equipment), labor (application time and skill requirements), and distance (transportation costs). Handling costs include storage requirements (some products need special storage conditions), safety equipment (some products require protective gear), and regulatory compliance (some products have special handling requirements). Including these would require many additional inputs and assumptions that vary by farm, location, and situation. This tool focuses on the simple comparison of product price per nutrient unit, which is one factor among many in fertilizer decisions. For comprehensive cost analysis, consider application and handling costs separately, or consult with local suppliers and applicators who understand your specific situation. Understanding why application costs aren't included helps you see this tool's focused purpose and when to use other resources.

A short ton is 2,000 pounds (lb), commonly used in the US for bulk fertilizer pricing. A metric ton (tonne) is 1,000 kilograms (about 2,205 lb). The tool handles both short tons and metric tons, as well as prices per pound or per kilogram. Make sure to select the correct price unit that matches how your supplier quotes prices. If your supplier quotes prices per short ton, select 'Short ton (2000 lb)'. If they quote per metric ton, select 'Metric ton (1000 kg)'. If they quote per pound or per kilogram, select those units accordingly. Using the wrong unit will give incorrect cost per unit calculations. Understanding price units helps you enter prices correctly and get accurate cost comparisons.

Yes, as long as you enter the correct analysis and price per mass unit. For liquid fertilizers, you may need to convert from price per gallon to price per lb or kg using the product density. The analysis percentages should be on a weight basis, which is how most liquid fertilizers are labeled. For example, UAN 28 (28-0-0) is typically sold by the gallon, but the analysis (28% N) is on a weight basis. To compare liquid and dry fertilizers, convert liquid price to price per pound or kilogram using the product density, then enter the analysis and converted price. The tool will calculate cost per unit of each nutrient for both products, allowing you to compare them on an equal basis. Understanding liquid fertilizer conversion helps you compare all fertilizer forms accurately.

Your agronomist considers many factors beyond price per nutrient unit: soil test results (shows actual nutrient needs and soil conditions), crop nutrient timing (when nutrients are needed affects which forms work best), secondary nutrients and micronutrients (some products provide additional nutrients not in NPK analysis), soil pH effects (pH affects nutrient availability and which forms work best), application method compatibility (some forms work better with certain application methods), and environmental considerations (some forms have lower environmental impact). The cheapest N source, for example, may not be appropriate for your soil or crop situation. A more expensive source might provide better nutrient availability, timing, or additional benefits that justify the higher cost. Understanding why agronomists recommend specific sources helps you appreciate the value of professional guidance and see cost per unit as one factor among many.

The analysis is printed on the fertilizer bag or product label as three numbers (e.g., 46-0-0 for urea, 18-46-0 for DAP). These represent the guaranteed minimum percentages of N, P₂O₅, and K₂O by weight. The first number is nitrogen (N), the second is phosphate (P₂O₅), and the third is potash (K₂O). The analysis is required by law to be on the label, so look for the three-number code. If you have a blend or custom product, your supplier can provide the analysis. Some products may also list additional nutrients (secondary nutrients like sulfur, calcium, or micronutrients) separately from the NPK analysis. Understanding where to find analysis helps you enter accurate values for cost calculations.

You can enter any fertilizer with known N-P₂O₅-K₂O analysis and price. However, organic fertilizers often have variable analysis (analysis can vary between batches), slower nutrient release (nutrients become available over time through mineralization), and provide benefits beyond NPK that are not captured in a simple cost comparison (improved soil health, organic matter, microbial activity). Organic certification and soil health goals may also influence your choices beyond simple cost per unit. If you're comparing organic fertilizers, be aware that the analysis may be lower and more variable than synthetic fertilizers, and the nutrient release timing is different. For organic fertilizers, consider the analysis as a starting point, but also consider the additional benefits and your organic certification requirements. Understanding organic fertilizer considerations helps you use this tool appropriately for organic systems.

If a product contains zero percent of N, P₂O₅, or K₂O, the tool will show 'no N', 'no P₂O₅', or 'no K₂O' for that nutrient. The product will not be ranked for that nutrient (won't appear as cheapest source). This is normal for single-nutrient fertilizers like urea (46-0-0, nitrogen only) or muriate of potash (0-0-60, potassium only). Products with zero percent of a nutrient simply don't provide that nutrient, so there's no cost per unit to calculate. When comparing products, focus on the nutrients each product provides. For example, if you need nitrogen, compare products that contain nitrogen. Understanding zero percent nutrients helps you see how single-nutrient fertilizers work and why they're not ranked for nutrients they don't contain.

Currently, the tool does not save product lists between sessions. You can use the copy feature to save results to your clipboard and paste them into a spreadsheet or document. For repeat comparisons, consider creating a simple spreadsheet with your common products, their analysis, and current prices. This allows you to quickly update prices and recalculate costs as market conditions change. Some users find it helpful to maintain a spreadsheet with their regular fertilizer products and update it periodically with current prices. Understanding saving limitations helps you plan how to track your fertilizer cost comparisons over time.

The tool handles unit conversions automatically, but understanding conversions helps you verify results. For imperial: 1 short ton = 2,000 lb, 1 metric ton ≈ 2,205 lb. For metric: 1 metric ton = 1,000 kg, 1 short ton ≈ 907 kg. To convert manually: Price per lb = Price per short ton ÷ 2,000, Price per kg = Price per metric ton ÷ 1,000. For liquid fertilizers, you may need density: Price per lb = (Price per gallon × Density in lb/gal), where density varies by product (e.g., UAN 28 has density ~10.6 lb/gal). The tool converts price units to base units (lb for imperial, kg for metric) before calculating cost per unit. Understanding unit conversions helps you verify calculations and work with different supplier price quotations.