The Internet's Finest Tropical Fruit Discussion Forum!"All discussion content within the forum reflects the views of the individual participants and does not necessarily represent the views held by the Tropical Fruit Forum as an organization."
Available water is the DIFFERENCE between field capacity which is the maximum amount of water the soil can hold and wilting point where the plant can no longer extract water from the soil. (Container grown trees included) The reasoning behind the 25 to 33 percent is that at or below those percentages, available water to the tree while still available, becomes harder and harder (slower and slower) for the tree's root system to extract from the soil. More and more of the trees energy is being used for less and less water.
beicadad, The above recommendations come from the monthly publication "The Citrus Industry".. During the hot months of the year a citrus tree can drink 30 to 130 gallons of water per day depending on the size of the tree. Water is especially needed during flowering/fruit set, and fruit enlargement.