Which item is listed under weather influences on irrigation planning?

• A. Rainfall
• B. Infiltration rates
• C. Compaction
• D. Salinity

Answer: (A)

Weather influences irrigation planning by directly changing how much water is available to crops and thus how much irrigation is needed. Rainfall is the prime example: when it rains, soil moisture increases and the irrigation schedule can be adjusted to avoid overwatering, delay irrigation, or stop irrigation altogether if the rainfall is ample. This makes rainfall the most straightforward weather factor in planning.

The other items are not weather factors themselves. Infiltration rates describe how quickly water moves into the soil, which depends on soil texture, structure, and moisture conditions, not the weather event itself. Compaction is a soil condition that affects how easily water enters and moves through the soil, again not a weather variable. Salinity concerns water and soil chemistry, which influence irrigation effectiveness and crop tolerance, but they are chemical properties rather than weather phenomena.