For simplicity, forage height can be used as an indicator for when to let animals into, and when to move them off, a pasture. The basic rule for the pasture species used in western Oregon is 8–12 inches to start grazing and 3–4 inches to stop grazing. This will protect plants from overgrazing, but does not provide specific information about available forage, which is required to determine stocking numbers and grazing duration.

Effect of grazing and mowing on root growth

Plant roots stay healthy when grazing severity is moderate and grazing periods are short with long rest periods. Root growth significantly decreases when grazing is continuous, and plants are given little time to recover.

Take half, leave half concept

Many ranchers in rangeland conditions (semiarid climate areas without irrigation) manage their pastures according to the principle of “take half, leave half.” This grazing philosophy has a scientific basis, assuming grazing is based on the appropriate starting point for plant height. As a general rule, removing up to 50% of leaf growth has minimal impact on root growth; however, once you remove more than 50% of shoots, root growth decreases significantly.