What is the thickness threshold for considering soil with coarse fragments in retention calculations?

In soil retention calculations, the threshold for considering the impact of coarse fragments—such as gravel and stones—on the soil's water retention capacity is set at 15%. This means that once coarse fragments make up 15% or more of the soil volume, their presence significantly affects how water is held in the soil. This is essential for accurately evaluating soil properties related to agriculture, infiltration, and overall water management. Coarse fragments do not retain moisture in the same way that finer particles do, so their presence needs to be factored into any retention calculations above this percentage to understand the soil's effective holding capacity. Therefore, recognizing the 15% threshold is crucial for accurate soil assessments and management practices.