How do you calculate soil porosity?

To calculate soil porosity, the appropriate formula involves understanding the relationship between bulk density and particle density. Soil porosity is defined as the volume of voids or pore spaces in a soil sample compared to the total volume of that sample. The formula for soil porosity is:

Porosity (%) = 100 - (Bulk Density / Particle Density * 100)

This indicates that soil porosity is derived from the ratio of bulk density (the mass of soil per unit volume that includes both soil particles and the spaces between them) to particle density (the mass of the soil particles only) expressed as a percentage.

Thus, by calculating the fraction of the volume that consists of solid matter (using bulk and particle densities) and converting that to a percentage, you can accurately determine how much of the soil's volume is made up of pores or spaces, which is crucial for understanding water retention, nutrient availability, and overall soil health within nutrient management practices.

The other options do not represent the correct calculation for soil porosity, as they either incorrectly manipulate the relationship between bulk and particle densities or describe a different measurement entirely.