Spring is an important and exciting time in agriculture. The perennial grasses that dominate our pastures have a lot of work to do this spring too. After a dry year and a harsh winter, these grasses initiate new growth from limited energy reserves.
At first, leaf area is small, and initial photosynthesis rates are not enough to meet the demands of the rapidly growing plants. So even though grass is greening up, it may still be using stored energy. If those first leaves are grazed off before energy reserves can be replenished, the grass may not have enough energy to regrow. Even when the grass is strong enough to regrow, it usually regrows slower.
Early season grazing can decrease production for the rest of the season. Some say that a day early in the spring can mean two or three days less grazing in the fall. Delaying the start of grazing until the main grass species has reached the three to four-leaf stage allows plants to recover better from grazing. However, it is not always possible to defer grazing on all paddocks until this stage.
When grazing early in the spring it is especially important to allow time for plant recovery in the rest of the grazing rotation. Grasses that have been well-rested will have greater energy reserves allowing them to better cope with spring grazing. A deferred rotation grazing system is desirable so that no one field is grazed first every year. Ideally, deferred grazing systems have at least three fields allowing the field grazed in the fall to be rested in the spring, and the field grazed in the spring to be rested for more than a full year. This reduces the stress of spring grazing each year and the selection pressure against early growing plants. A deferred rotation can support spring grazing by allowing for plant recovery.
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