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Calcimator

Organic Matter Building Calculator

Estimate years to reach your soil organic matter target based on compost, cover crops, manure additions, decomposition rate, and tillage intensity.

Inputs

%
%
%

Results

Years to Target OM

-1

Total Cost to Target ($/acre)

-$1.00

Annual Stable OM Added (lbs/acre)1,326
Annual Amendment Cost ($/acre)$135.00
Water Holding Gain (gal/acre)30,000
OM Gap (%)1.5
Total OM Needed30,000
How to Use This Calculator
  1. Enter current soil organic matter (SOM %) from a recent lab analysis.
  2. Enter annual compost or manure application rate (tons/acre) and carbon-to-nitrogen ratio of amendments.
  3. Enter tillage intensity level and expected annual SOM decomposition rate (%).
  4. Read projected SOM (%) after specified years and annual carbon sequestration (tons C/acre).
  5. Use results to track progress toward soil health program benchmarks and verify amendment rates.

What each input means

Current Soil OM (%)
Current soil organic matter percentage from soil test.
Target Soil OM (%)
Desired soil organic matter percentage.
Compost (dry tons/acre/year)
Annual compost application in dry tons per acre.
Cover Crop Biomass (dry tons/acre/yr)
Annual dry matter from cover crops returned to soil.
Manure (dry tons/acre/year)
Annual composted manure application (NOP requires composting).
Annual OM Decomposition (%)
Annual rate existing SOM decomposes (1-2% cool, 2-3% warm climates).
Tillage Intensity (0-3)
0 = no-till, 1 = reduced tillage, 2 = conventional, 3 = intensive.
Soil Depth (inches)
Depth of soil being managed (typically 6 inches for plow layer).

What each result means

Years to Target OM
Estimated years to reach target organic matter level (-1 = unreachable).
Annual Stable OM Added (lbs/acre)
Pounds of stable humus added to soil per acre annually.
Annual Amendment Cost ($/acre)
Estimated cost per acre for compost, cover crops, and manure.
Total Cost to Target ($/acre)
Cumulative cost per acre to reach target OM (-1 = unreachable).
Water Holding Gain (gal/acre)
Estimated improvement in soil water holding capacity.
OM Gap (%)
Percentage points of organic matter to build.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Current Soil OM (%) = 2.5, Target Soil OM (%) = 4, Compost (dry tons/acre/year) = 3, Cover Crop Biomass (dry tons/acre/yr) = 2 = 8 input(s) provided
  2. Calculate Years to Target OM
    -1 = -1
  3. Calculate Total Cost to Target
    -1 = $-1
  4. Calculate Annual Stable OM Added
    Annual Stable OM Added = compostContribution + coverCropContribution + manureContribution
    1326 = 1326
  5. Calculate Annual Amendment Cost
    Annual Amendment Cost = compostCost + coverCropCost + manureCost
    135 = $135

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