How many inches of water must be used on a plant with an 18" root depth, due to slow permeability of clay?

In this scenario, with a plant that has an 18-inch root depth and is growing in clay soil known for its slow permeability, the correct amount of water that must be applied is 3 inches.

Clay soils have a small particle size and tightly packed structure, which means they retain water well but also slow down the rate at which water can infiltrate. When watering plants in such soils, it’s important to apply enough water to penetrate deeply into the root zone to ensure that the entire depth of the root system can access moisture.

Given that the plant’s roots extend to 18 inches, the application of 3 inches of water allows for sufficient penetration while taking into account the slow uptake characteristics of clay. This volume helps ensure that the moisture reaches the lower sections of the root system, which is essential for healthy plant growth, especially during dry periods. A less substantial amount of water may only saturate the upper layer and leave the deeper roots underserved. Thus, applying 3 inches in this context is an appropriate recommendation to accommodate the specific conditions presented.