When determining water retention, which formula is used?

The correct answer involves calculating water retention by acknowledging the depth or thickness of the soil layer being considered and adjusting for the influence of rock content, which does not retain water. Water retention is an important characteristic of soil, as it influences both plant growth and water management practices.

In this case, the thickness of the soil is multiplied by a factor that represents the soil's water-holding capacity, and then further adjusted by subtracting the proportion of rock content. This adjustment is crucial because rocks do not contribute to the soil's ability to hold water; therefore, the greater the rock content, the lower the effective water retention capacity of the soil.

By using this formula, one can accurately estimate the volume of water that the soil can retain, enabling better agricultural and environmental decisions related to irrigation and land use.