Time is more important than numbersHere's a statement that provides a challenge to conventional wisdom: You cannot overgraze a paddock!
Principle Number 5 says that only a plant can be overgrazed, which immediately raises the question, "What exactly is 'overgrazing'?". The answer is: "Overgrazing is the second or further bite of a plant, before it has fully recovered from a previous bite."
Overgrazing occurs to individual plants, and it happens plant, by plant, by plant. It can only occur when one of two specific conditions exist:
1) Animals remain too long in a paddock under fast growth conditions; orWhen animals remain too long in rapid growth
2) Animals return to a paddock (and therefore its plants) too soon in periods of slow growth.
If one or more animals remain in a paddock long enough that they again bite a plant (or many plants) that have produced fresh growth after an earlier bite taken during the same visit, the plants involved are overgrazed. You can get an idea of how quickly plants might become at risk by noting how quickly a paddock displays 'green-up' once animals are removed. You'll notice that under the right conditions it can be very fast. Under appropriate moisture and temperature conditions, new edible leaf can be visible within just a few hours, and often within a day or so.
This spurt of post-grazing growth comes from stored root energy moving upwards to form new leaf. As part of the process but not visible because it happens below ground level, the portion of a plant's roots that deliver this energy to its leaves, will die. If this is allowed to occur regularly there is a compounding effect. The plants root resources are increasingly depleted, and eventually plant death(s) begin.
When animals return too soon in slow growth
This scenario is far more common, and usually much more damaging because many more plants are usually involved. When animals return too soon to a paddock, they return to a situation where almost every plant that was bitten the last time the animals were in the paddock are not yet fully recovered. When plants are only partially recovered they have not yet fully developed the complete new root structure necessary to replace the roots killed off in the process of recommencing growth. NOTE: The process of 'recovery' means growing an entirely new root system. It is not just reconstructing the framework of an old root system.
The essence of holistic grazing planning is to be constantly matching the speed of animal moves to the physical rate of plant recovery. This rate or speed of recovery changes constantly in response to variations in soil moisture and atmospheric humidity, soil and atmospheric temperatures, litter cover, microbiological activity, and much more.
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