In soil moisture terms, what does field capacity refer to?

• A. The minimum soil moisture required for plant growth
• B. The maximum amount of water soil can hold before free water appears on the surface
• C. The amount of water drained after irrigation ends
• D. The water content when soil pores are completely empty

Answer: (B)

Field capacity is the amount of water the soil holds after gravity drainage has ceased, meaning the soil has drained to a point where free water no longer drains to the surface. It represents the water retained in the smaller, capillary pore spaces that resist gravitational loss, and it marks the upper limit of plant-available water for a given soil texture. Practically, if soil is saturated and allowed to drain, it will reach this moisture level; adding more water will cause surface water to appear. This is why this choice describes field capacity as the maximum water the soil can hold before free water shows up on the surface. The other ideas describe different moisture states: the minimum moisture for growth aligns more with the lower bound of available water, not field capacity; the water drained after irrigation ends refers to the drainage that occurs from saturation down to field capacity; and water content when pores are completely empty corresponds to near oven-dry conditions, which is far from field capacity.