Define field capacity and wilting point, and explain their roles in predicting plant water stress and irrigation scheduling.

• A. Field capacity is the soil moisture content after drainage by gravity; wilting point is the water content at which plants cannot recover from wilting. The available water (FC minus WP) guides irrigation scheduling to prevent water stress.
• B. Field capacity equals wilting point; both represent fully saturated soils.
• C. Wilting point is the water content at which soils are fully drained.
• D. Available water is field capacity plus wilting point.

Answer: (A)

Field capacity and wilting point define how much water in the soil a plant can actually use. Field capacity is the soil moisture content after gravity drainage has ceased, essentially the amount of water the soil holds when free drainage stops and the pores are filled to a stable level. Wilting point is the water content at which plants can no longer extract enough water to recover from wilting, so once the soil dries to this point, recovery is unlikely without rehydration. The water available to plants in the root zone is the difference between field capacity and wilting point, often called available water. This quantity is what irrigation scheduling relies on: keep soil moisture above the wilting point to prevent stress, and manage irrigation so you don’t exceed field capacity to minimize water loss through drainage. In practice, irrigation is planned to replenish the available water pool as it’s used by the crop, maintaining soil moisture within a range that supports healthy growth without waste. The other statements mix up these concepts or the arithmetic—for example, field capacity does not equal wilting point, wilting point is not simply the point where soils are fully drained, and available water is not the sum of the two.