Why should students stop at a lithic or paralithic layer during soil assessments?

Stopping at a lithic or paralithic layer during soil assessments is crucial because these layers represent the transition from the soil profile to bedrock or partially weathered rock. Lithic layers are solid bedrock, while paralithic layers consist of weathered rock that is still too hard to be considered a part of the soil, although it may have some soil characteristics.

When conducting soil assessments, the maximum depth of evaluation is determined by these layers, as they signify the limit of the soil profile where significant soil-forming processes can occur. Below these layers, the physical and chemical properties of the material change dramatically, typically leading to a lack of further development of soil horizons. Therefore, exploring deeper into these layers would provide little useful information regarding the soil's potential for crops, its drainage characteristics, or its management needs.

Recognizing the maximum depth at which you can evaluate soil properties ensures that assessments focus on the layers where biological activity, nutrient availability, and other soil processes are occurring. Collecting data beyond this depth would likely not provide insights relevant to soil health, fertility, or suitability for various land uses.