Science and logic for good grazing management

Overgrazed pastures typically recover far slower when rain does occur with many associated adverse outcomes. These include more water runoff (with less available for pasture growth), often greater plant losses, lower seed set and much less total pasture growth.

Other aspects of grazing management are important but nothing is more critical than adequate groundcover. Pastures are like miniature “solar panels” and if not allowed to develop sufficient leaf area they fail to grow anywhere near their maximum. Ability to grow at maximum rate is a balance between not being too high and thick when bottom leaves begin to be smothered and die off (which generally doesn’t occur until drymatter levels are around 3.0 - 4.0 t/ha) and too low with insufficient leaf area.

While it is tempting to use all available feed in dry times, if it affects regrowth and total productivity after breaking rains it is not in the long run best management. Annual legumes respond more to groundcover and density levels for growth rates. It is important to allow aerial flowering and seeding species to set good levels of seed reasonably often.  

Probably the most important aspect for many soils and terrains in maintaining good groundcover is the ability to effectively capture rain when it does occur. Low groundcover levels lead to big water losses should the rain event be other than slow and prolonged. Water is like good soil fertility critical to effective pasture growth.

Scientifically documented grazing management research has focused on a multitude of situations including different species and environments and has arrived at a variety of conclusions as to what is best grazing management.

Lucerne is well studied. Best persistence occurs with a combination of relatively short periods of grazing (one to three weeks) and for recovery to reach around 10 percent flowering in spring summer and to mid-autumn. In the warmer months that is a recovery period of around 42 days to result in maximum root reserves recovery.

While physiological studies are limited for perennial grasses, native and introduced, also appear to need recovery periods to replenish root reserves and to provide opportunities for recruitment and new plant establishment. Desirable grazing duration and recovery time for actively growing perennials is species as well as environment and current season related. Good groundcover seems to be a critical consideration.

A major northern tablelands study (Cicerone), involving producers, researchers and extension specialists, found that high soil fertility and pasture renovation enhanced productivity more than any given grazing management, without imposing risks to the environment. An Extensive grazing system study conducted by CSIRO and Queensland DPI (MLA funding) on nine properties, noted that grazing system had little impact on pastures or soil surface condition. A recent issue of African Journal of Range and Forage Science noted that broad generalisations of grazing management type commonly was not supportive of any given system.

Some perennials can survive greater depletion of root reserves (example red grass) or can build or maintain them over longer grazing periods than other (Kangaroo grass). Also in any native or introduced pasture there generally is a mixture of palatable, moderately palatable and relatively unpalatable species. If stocked for lengthy periods unpalatable species rarely grazed have a selective advantage. 

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