Proper irrigation is essential to maintaining a healthy and productive orchard. Over-irrigation slows root growth, increases iron chlorosis in alkaline soils, and leaches nitrogen, sulfur, and boron out of the root zone, leading to nutrient deficiencies. Over-irrigation can also induce excessive vegetative vigor, and reduce fruit size.
Excessive soil moisture also provides an environment ideal for crown and collar rots. Applying insufficient irrigation water results in drought stress and reduced fruit size and quality.
Properly managing irrigation is analogous to managing money. In addition to knowing your current bank balance (soil water content), it is important to track both expenses (evapotranspiration) and income (rainfall and irrigation).