State Institution
Institute of Soil Protection of Ukraine

(044)-356-53-21
Логотип

State Institution
Institute of Soil Protection of Ukraine

  • Укр
  • Eng

Calculation details

This page contains the formulas, explanations, and all reference tables used in the calculation.

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How it works

This page contains formulas and reference tables. The actual calculation happens in the calculator on the previous page — that is where you enter data and get results.

  • Open the calculator and choose the method and nutrient (N / P₂O₅ / K₂O).
  • Enter planned yield, nutrient removal, utilization coefficients, and (if needed) soil stock.
  • If soil stock is unknown, click “Calculate P by formula”.
  • The calculator computes required active ingredient Kne (kg/ha) for the chosen method.
  • Then it converts to fertilizer physical rate (kg/ha) and total amount for the area.

Abbreviation explanations

Short explanations of the abbreviations used in the forms and formulas.

  • Bne — active ingredient percentage in the selected fertilizer, %.
  • Removal V — nutrient removal per 1 centner of yield, kg/cwt.
  • Up — planned yield, cwt/ha.
  • Kg — soil utilization coefficient, %.
  • U — mineral fertilizer utilization coefficient, %.
  • Soil stock P — nutrient stock in soil, kg/ha.
  • Gn — organic fertilizer rate, t/ha.
  • Hv — nutrient content in 1 t of organics, kg.
  • β₁ — utilization from organics in year 1, %.
  • β₂ — utilization from organics in year 2, %.
  • Nm″ — nutrient applied to the predecessor with mineral fertilizers, kg/ha.
  • U″ — mineral aftereffect utilization, %.
  • a — nutrient content in soil, mg/kg.
  • d — bulk density of the arable layer, g/cm³.
  • h — arable layer depth, m.
  • Kne — required active ingredient rate, kg/ha.
  • Kd — fertilizer rate (physical mass), kg/ha.

Calculation methodology

Below are formulas and calculation steps used in this calculator.

Formula 1 (Balance method): N = (100 × Up × V − P × a − Gn″ × Hv × β″ − Nm″ × U″ − Gn × Hv × β) / U Formula 2 (Balance-calculation method): N = (100 × Up × V − P × Kg − Gn × Hv × β) / U Soil stock formula: P = a × d × h × 10 Conversion to fertilizer physical rate: Kd = Kne × 100 / Bne

Reference tables used in calculations

Dropdown options are based on the fertilizer reference and active nutrient content.

Basic mineral fertilizers

Fertilizer Chemical formula Active ingredient, % Effect on soil

Complex mineral fertilizers

Fertilizer N, % P₂O₅, % K₂O, %

Table 2.2. Crop nutrient removal

These values are used to auto-fill the `Removal V, kg/c` field after crop selection.

Crop N P₂O₅ K₂O

Table 2.3. Mineral fertilizer utilization coefficient

Values are auto-filled into the `Mineral utilization coef. U, %` field based on crop, soil group, and soil stock.

Soil group Crop N up to 50 N 50-100 N 101-150 P₂O₅ up to 50 P₂O₅ 50-100 P₂O₅ 101-150 K₂O up to 50 K₂O 50-100 K₂O 101-150

Maximum nitrogen doses

Maximum allowed nitrogen doses by soil-climatic zone (kg/ha of active ingredient).

Crop Polissya Forest-steppe Steppe