Fertilizer Calculator

Free reference guide: Fertilizer Calculator

26 results

About Fertilizer Calculator

The Fertilizer Calculator Reference is a searchable guide covering 27 topics essential for agricultural fertilizer planning and nutrient management. The Nitrogen Fertilizer section details urea (N 46%), ammonium sulfate (N 21%, S 24% for alkaline soils), and ammonium nitrate (N 34% with both NH4+ and NO3- forms). Phosphate entries cover fused phosphate (P2O5 20%, SiO2 25%, MgO 15% for acidic paddy soils), single superphosphate (P2O5 17-20%), and triple superphosphate (P2O5 44-46%). Potash options include potassium chloride (K2O 60%, avoid for tobacco/potato) and potassium sulfate (K2O 50%, S 18% for high-quality crops).

Compound fertilizer entries explain 21-17-17 general-purpose NPK, NK formulations for phosphorus-excess soils, and slow-release coated fertilizers (LP40 through LP140 with 40-140 day release). Soil amendment topics cover lime requirement calculation using SMP buffer pH method, silicate fertilizer for rice lodging prevention (SiO2 25%+, 150-200 kg/10a), and dolomite (CaO 30%, MgO 15%) for acidity correction. Crop-specific fertilization rates provide standard N-P2O5-K2O values for rice (9-11, 4.5-5.7, 5.7-8.0 kg/10a), pepper, fall cabbage, apple trees, and greenhouse tomato with timing splits.

Application method entries detail foliar feeding concentrations (urea 0.5-1.0%, potassium phosphate 0.3-0.5%), fertigation EC management by crop (tomato 2.0-3.0 dS/m, strawberry 0.8-1.2 dS/m), side-dressing placement (5-10cm lateral, 5cm below seed), slow-release single-application technology, and fertilizer mixing compatibility rules. Calculation formulas include nutrient content conversion between bulk weight and nutrient weight, and soil test-based correction coefficients from 1.5x (very low) down to 0x (very high) for adjusting standard application rates.

Key Features

Nitrogen fertilizer specifications: urea (N 46%), ammonium sulfate (N 21%, S 24%), ammonium nitrate (N 34%) with conversion calculations for target N rates
Phosphate and potash options: fused phosphate for paddy soils, SSP/TSP for upland, KCl (K2O 60%, avoid tobacco/potato) vs K2SO4 (K2O 50% for quality crops)
Compound fertilizer reference: 21-17-17 NPK with deficit supplementation, NK for P-excess soils, LP coated slow-release (40-180 day dissolution)
Soil amendment calculations: SMP buffer pH lime requirement, silicate for rice lodging (150-200 kg/10a), dolomite CaO 30%/MgO 15% acidity correction
Crop-specific standard rates for rice, pepper, cabbage, apple, and greenhouse tomato with base/top-dressing timing splits
Fertigation EC management: tomato 2.0-3.0 dS/m, strawberry 0.8-1.2 dS/m, paprika 2.5-3.5 dS/m with pH 5.5-6.5 targets
Fertilizer mixing compatibility rules: prohibited combinations (lime + ammonium sulfate, urea + SSP) and safe mixes (urea + KCl)
Nutrient conversion formula (bulk = nutrient / content% x 100) and soil test correction coefficients (very low 1.5x to very high 0x)

Frequently Asked Questions

What fertilizer types does this reference cover?

It covers three single-nutrient categories (nitrogen: urea, ammonium sulfate, ammonium nitrate; phosphate: fused phosphate, SSP, TSP; potash: KCl, K2SO4), compound fertilizers (21-17-17 NPK, NK, slow-release LP coated), soil amendments (lime, silicate, dolomite), crop-specific rates for five crops, four application methods, and two calculation formulas.

How do I calculate how much urea to apply for a target nitrogen rate?

Use the conversion formula: bulk weight = nutrient weight / content percentage x 100. For example, if you need 15 kg of nitrogen (N), calculate 15 / 46 x 100 = 32.6 kg of urea. Conversely, 50 kg of urea provides 50 x 46 / 100 = 23 kg of N.

Why should I choose K2SO4 over KCl for certain crops?

Potassium chloride (KCl, K2O 60%) is cheaper but contains 47% chlorine, which reduces starch content in potatoes and sweet potatoes and negatively affects quality of tobacco, fruits, and vegetables. Potassium sulfate (K2SO4, K2O 50%, S 18%) is chlorine-free and also supplies sulfur, making it the preferred choice for high-quality crop production.

What is the standard rice fertilization schedule?

Rice requires N 9-11, P2O5 4.5-5.7, K2O 5.7-8.0 kg per 10a (1000 sq meters). The timing split is: basal application (N 50%, P 100%, K 70%), tillering stage (N 20-30%), and panicle initiation (N 20-30%, K 30%). This schedule should be adjusted based on soil test results using correction coefficients.

How do I calculate lime requirements for pH correction?

Use the SMP buffer pH method. At buffer pH 6.5, apply approximately 200 kg/10a of dolomitic lime. At pH 6.0, increase to 350 kg/10a, and at pH 5.5, apply 500 kg/10a. One pH unit correction typically requires 200-300 kg/10a of dolomite. Be cautious of over-liming, which can cause micronutrient deficiencies.

What fertigation EC levels should I target for greenhouse crops?

Target EC ranges are: tomato 2.0-3.0 dS/m, strawberry 0.8-1.2 dS/m, and paprika 2.5-3.5 dS/m. Maintain pH between 5.5 and 6.5. Fertigation frequency varies from 3 to 8 times daily depending on growth stage, with nutrient solution concentration adjusted throughout the crop cycle.

Which fertilizers should never be mixed together?

Prohibited combinations include: lime + ammonium sulfate (causes ammonia volatilization), lime + superphosphate (phosphorus fixation into insoluble forms), and urea + superphosphate (excessive moisture absorption). Safe combinations include urea + potassium chloride, and compound fertilizer + potassium sulfate.

How do I adjust fertilization rates based on soil test results?

Apply correction coefficients to standard rates: very low soil test = 1.5x standard rate, low = 1.2x, adequate = 1.0x (standard), high = 0.5x, and very high = 0x (no fertilization needed). This prevents both under-fertilization and excessive application that leads to environmental pollution and nutrient imbalances.