When a fragipan is present, AWHC should be calculated how?

• A. Include layers below fragipan in AWHC calculation
• B. Exclude layers below fragipan in AWHC calculation
• C. Include only above the topsoil above 6 inches
• D. It does not affect AWHC calculations

Answer: (B)

AWHC reflects the amount of water plants can actually use in the effective rooting zone. A fragipan is a dense, restrictive layer that slows water movement and limits root penetration, effectively isolating the deeper soil from the roots. Because water stored below the fragipan is not readily accessible to plants under normal conditions, those layers shouldn’t be counted in AWHC. So, the calculation should include only the soil above the fragipan and exclude layers below it. Including deeper layers would overstate what the plant can use, and treating only the top 6 inches or saying it doesn’t affect AWHC would not accurately reflect the rooting environment shaped by the fragipan.