Grazing

‘Grazing’ happens to plants, and never to paddocks, blocks, pastures or veldt—you select the word depending on where in the world you live!  By definition, grazing is a tool that requires animals to be present and active. Much of the discussion here revolves around grasses, but the same principles apply for shrub plants and trees that are browsed.

Here’s an interesting thought: as you move through this page you will discover that proper grazing management is vital for the health of plants.  Most people know that grass is essential for the well-being of grazing animals, but few people recognise how important the animals are for the well-being of the plants.

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There are two ways that the tool of Grazing can be used:
  • ‘Grazing’, which fosters and maintains healthy, normal plants
  • ‘Overgrazing’, which leads to deformed plants with lower productive capacity.
If a plant is not grazed or overgrazed, then it will be overrested.

1. ‘Normal’ or healthy plants
When an individual perennial grass plant is grazed (whether lightly topped or severely defoliated), it is commonly invigorated and its life prolonged.  Over millions of years the bulk of perennial grass plant species coevolved with herding animals that graze severely.  As a result, many species of grass plants have developed growth points that are located out of harm’s way, close to the soil surface. The plant shown in the photograph below is erect and dense.  It has the structure of a ‘normal’ plant.  This plant is adapted to a regular program of severe grazing followed by adequate recovery time, and it can sustain this graze:recover regime for many years—for perhaps much of a human lifetime.  These plants really are a biological and financial asset to a farmer.



2. Overgrazed plants
As discussed in role of time graph, when normal plants who have their growth points down near the soil surface are grazed too frequently ie before they are fully recovered from a previous grazing, will, over time become deformed, and are then said to be ‘overgrazed’.   

You can quickly identify an overgrazed plant as it will tend to grow prostrate to the ground rather than erect, as the photo below shows. In this photo,  notice that the centre has very little emerging vegetation, and the few leaves that exist are growing sideways rather than erect.  The plant is effectively a damaged and deformed ‘solar panel’, capturing little sunlight and contributing little to the wealth of the farmer.



Plants develop the prostrate growth habit because as their mechanism for avoiding the ‘marauding mouths’ of grazing animals who are able to constantly return to them before they are fully recovered.  For otherwise healthy plants there are just two conditions that expose them to the risk of overgrazing:
  • Animals remaining too long in a paddock in periods of rapid growth
  • Animals returning to a paddock too soon in periods of slow growth
The second scenario is the most common, and most devastating over the long term.  The graph below shows the various parts of the growth cycle of a plant (whether annual or perennial).  You can quickly see that set stocking of animals is potentially very damaging to the health of the plants, because animals are always present and might nip short, new growth, time after time, after time.

Equally, any form of rotational grazing that does not adjust speed of moves to the dynamic and constantly changing plant recovery times creates the risks (if not certainty) of returning animals to a paddock too soon, whilst many or most plants are still low down on the plant recovery curve.  

Note: Returning a bit too late, or when their growth curve is at, or near the apex, does not cause significant problems to plants, although there may be a slight drop off in both plant productivity and animal performance.

Here is the “Golden Rule” and the most important part of this page.  You will ignore this at your peril!!

In periods of rapid growth you should move the animals quickly.
(That is: recovery periods can be shortened)

In periods of slow growth you MUST move the animals slowly.
(That is: grazing periods per paddock must be lengthened to match slow plant recovery rates)




3. Plants adapted to over-rest
Some bunched perennial grass plants are not dependent on severe grazing to sustain their health.  Such grasses are commonly found to have growth points along their stems, located well above the soil surface.  These plants are well adapted to over-rest.  Because they are adapted to over-rest they are also adapted to poor ecosystem function, and tend to grow much less bulk of material than normal, healthy plants.  

The plant below is adapted to over-rest.  The arrow points to the aerial growing point.  Notice that the growing point is a nice straw colour, whereas the balance of the plant is grey, and slowly oxidising away.  It is extremely unpalatable to most grazing animals, even to ruminants who can process significant amounts of lignified material. (Note: this photo is acknowledged as taken by Allan Savory).



In Australia, many of the remaining perennial grass plants exhibit form like the plant above.  Many of the ‘windmill’ grasses (chloris spp), aristida spp, and some of the stipa spp have variations of this theme.

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