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Agricultural Tool

Organic Matter Nitrogen Mineralization / Immobilization Calculator

Estimate whether an organic amendment will release nitrogen (mineralization) or temporarily tie up nitrogen (immobilization).

Organic Material Details

kg/ha
Dry matter basis
%
Allowed range 1 – 70%
C : N
Must be greater than zero
Advanced Settings
%
Default 35%
C : N
Default 8
Outcome

Net Nitrogen Mineralization

0 kg N/ha

Mineralization Immobilization
Strong N release Balanced Strong N tie-up
Carbon supplied
0
kg C/ha
N in residue
0
kg N/ha
Microbial N demand
0
kg N/ha
Critical C:N
0
break-even ratio

Interpretation & Recommendations

Interpretation

    Understanding Mineralization and Immobilization

    Mineralization

    Occurs when organic residues contain more nitrogen than the decomposing microbes require. The surplus is released to the soil as plant-available ammonium and nitrate.

    Well decomposed compost Poultry manure Legume residues Low C:N materials

    Immobilization

    Occurs when microbes must draw additional nitrogen from the soil to decompose carbon-rich residues. Soil nitrogen is locked in microbial biomass until decomposition slows.

    Rice straw Wheat straw Sawdust Wood chips Fresh maize stalks High C:N compost

    General guideline

    C:N ratioExpected outcome
    Below 20Usually mineralization
    20 – 25Transition zone
    Above 25Usually immobilization

    How the calculation works

    Carbon (kg) = Organic material × Carbon% ÷ 100
    Nitrogen in residue (kg) = Carbon ÷ C:N ratio
    Microbial carbon (kg) = Carbon × CUE ÷ 100
    Microbial N demand (kg) = Microbial carbon ÷ Microbial biomass C:N
    Nitrogen balance (kg) = Nitrogen in residue − Microbial N demand

    With the default settings the balance turns negative once the material's C:N ratio exceeds the critical C:N ratio = microbial biomass C:N ÷ CUE = 8 ÷ 0.35 ≈ 22.9, which is why the 20–25 band behaves as a transition zone. Changing CUE or the microbial biomass C:N in Advanced Settings moves this threshold.

    Disclaimer: This calculator provides a theoretical estimate based on microbial carbon use efficiency and microbial biomass C:N ratio. Actual nitrogen mineralization depends on soil temperature, moisture, aeration, residue quality, soil microbial activity, pH, and management practices. Results should be used as guidance rather than exact field predictions.