Rangeland Soil Practice Exam

What is soil organic matter and how does it influence soil properties?

Soil organic matter is inert rock fragments; it reduces water retention. Soil organic matter is decomposed plant and animal residues; it promotes stable soil aggregates and increases water retention. Soil organic matter is soluble salts; it has no effect on water. Soil organic matter is only microbial biomass; it decreases aggregation.

Correct Answer:

Soil organic matter is decomposed plant and animal residues; it promotes stable soil aggregates and increases water retention.

Explanation:

Soil organic matter is decomposed plant and animal residues along with the living components and byproducts that accumulate in the soil. This material isn’t inert; it acts like a natural binder and sponge. It helps soil particles stick together to form stable aggregates, which creates a better soil structure with both small and large pores. That improved structure enhances water infiltration, reduces crusting, and increases the soil’s capacity to hold water for plants. So, the best description is that soil organic matter promotes stable soil aggregates and increases water retention. It also contributes nutrients and microbial habitat, but the key functional point here is the promotion of aggregation and greater water-holding capacity.

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