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Agronomy QUESTION #2055
Question 1
The permanent wilting point (PWP) of soil is the moisture content at which:
  • All gravitational water has drained from the soil macropores
  • Plants can no longer extract sufficient water from the soil and wilt permanently, corresponding to a soil matric potential of approximately \(-1500\) kPa (or \(-15\) bar)✔️
  • Soil moisture equals 50% of field capacity
  • Surface evaporation exceeds plant transpiration
Correct Answer Explanation
PWP is the soil moisture content at which the remaining water is held so tightly by soil particles (matric potential ≈ −1500 kPa) that roots cannot exert sufficient suction to extract it. Plants wilt permanently — they do not recover even when placed in a humid atmosphere. Plant-available water = FC − PWP.