Substrate Bulk Density Porosity

Derive substrate pore water/air partition from measured saturated and drained core masses; distinct from geology porosity inferred from assumed particle density, requiring full wetting and no core swelling.

Description

Substrate pore water and air can be measured using dry, saturated and drained core masses.

Substrate pore water and air can be measured using dry, saturated and drained core masses. Full saturation and a fixed core volume are needed for the mass differences to represent pore volume.^[1]

When to use Substrate Bulk Density Porosity

Use this tool to derive substrate pore water/air partition from measured saturated and drained core masses; distinct from geology porosity inferred from assumed particle density, requiring full wetting and no core swelling.

Prepare the plant, nutrient, light or scheduling measurements for the intended crop and period. Keep paired records aligned and confirm units and supplied target values.

How to use Substrate Bulk Density Porosity and understand its results

Prepare the plant, nutrient, light or scheduling measurements for the intended crop and period. Keep paired records aligned and confirm units and supplied target values.
Enter coreVolumeCm3, ovenDryMassGrams, saturatedMassGrams, drainedContainerCapacityMassGrams, waterDensityGramsPerCm3 using the field table and calculation rules, then run the tool.
Read dryBulkDensityGramsPerCm3, measuredTotalPoreFraction, containerCapacityWaterFraction, airFilledPoreFraction. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
coreVolumeCm3	Core volume cm3	number	Required
ovenDryMassGrams	Oven dry mass grams	number	Required
saturatedMassGrams	Saturated mass grams	number	Required
drainedContainerCapacityMassGrams	Drained container capacity mass grams	number	Required
waterDensityGramsPerCm3	Water density grams per cm3	number	Required

Use positive core cm³ and water g/cm³, with nonnegative masses ordered dry≤drained≤saturated. Require total measured pore fraction ≤1. Return dry bulk density, total porosity, drained water fraction and air-filled fraction.

total pore fraction=(saturated−dry)/(water density × volume); air fraction=(saturated−drained)/(water density × volume)

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
dryBulkDensityGramsPerCm3	Dry bulk density grams per cm3	number
measuredTotalPoreFraction	Measured total pore fraction	number
containerCapacityWaterFraction	Container capacity water fraction	number
airFilledPoreFraction	Air filled pore fraction	number

json

{
  "input": {
    "coreVolumeCm3": 100,
    "ovenDryMassGrams": 20,
    "saturatedMassGrams": 90,
    "drainedContainerCapacityMassGrams": 60,
    "waterDensityGramsPerCm3": 1
  },
  "output": {
    "dryBulkDensityGramsPerCm3": 0.2,
    "measuredTotalPoreFraction": 0.7,
    "containerCapacityWaterFraction": 0.4,
    "airFilledPoreFraction": 0.29999999999999993
  }
}

Limitations and assumptions

Core swelling, incomplete wetting and trapped air violate the measurement assumptions. Particle-density-derived porosity is a different method.

Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Peat Perlite Bark Blend Ratio Mixer: Scale caller peat/perlite/bark loose-volume ratios to a calibrated settled blend volume and balance dry/water masses; no additive pore-volume, pH or fertility guarantee. For a complementary task, use Skid Trail Bulk Density Compaction Percent Increase: Compare matched dry bulk-density cores using paired and physical-volume-weighted contrasts, preserving apparent decompaction; unlike simple porosity conversion, no compaction damage or trafficability conclusion.

References

Substrate Bulk Density Porosity — tool.io

Similar or alternative tools

Peat Perlite Bark Blend Ratio Mixer
Scale caller peat/perlite/bark loose-volume ratios to a calibrated settled blend volume and balance dry/water masses; no additive pore-volume, pH or fertility guarantee.
Skid Trail Bulk Density Compaction Percent Increase
Compare matched dry bulk-density cores using paired and physical-volume-weighted contrasts, preserving apparent decompaction; unlike simple porosity conversion, no compaction damage or trafficability conclusion.