Which of the following is a soil factor affecting infiltration in irrigation design?

• A. Infiltration rates
• B. Rainfall
• C. Temperature
• D. Evapotranspiration

Answer: (A)

Water entering soil is governed by the soil’s physical properties that determine pore space and how easily water moves through the soil. The infiltration rate is a direct expression of those properties, reflecting texture (sand, silt, clay), soil structure, compaction, surface sealing, moisture content, and organic matter. In irrigation design, knowing the infiltration rate helps you size water applications and prevent runoff or deep percolation by matching flow rate and application time to how quickly the soil can absorb water. Weather factors like rainfall, temperature, and evapotranspiration influence how much water is available or lost, but they are not soil properties themselves and don’t define the soil’s capacity to absorb water.