Which pore type is primarily associated with plant available water?

• A. Macropores
• B. Micropores
• C. Total porosity
• D. Gaseous pores

Answer: (B)

Plant available water comes from the water stored in the smallest pore spaces, where capillary forces hold water at a suction level roots can pull. Large pores are macropores; they drain quickly under gravity and mostly contain air or water that isn’t readily accessible to plants. Water in these big pores is not held for plant use as effectively. Micropores, by contrast, trap water tightly enough to be held between field capacity and wilting point but still within reach of roots, making them the main source of water plants can extract during dry periods. Total porosity includes both big and small pores, but it doesn’t indicate how much of that space actually contributes to plant-available water. Gaseous pores are air-filled and do not contain usable water. So the pore type most associated with plant available water is micropores.