Managing Native Pastures

While there is no set recipe for managing native pastures, some basic principles apply to all perennial-based pastures.  Management should consider the:

• effect of defoliation on the ability of the plant to withstand drought;
• effect of soil cover on the rate of soil erosion;
• need for seedling opportunities that allow recruitment and replenishment of soil seed bank;
• likely benefit of diversity of species on drought tolerance;
• effect of overgrazing on pasture composition; and
• benefits of periodic resting.

These principles are the same as those for introduced perennial pastures, with the added complicating factor that many more species occur in a native pasture.  As with all pastures, the key is to have a flexible system that can be changed as the season, pasture and stock require.

The most important principle is that stocking rates need to be matched to forage availability (this will vary seasonally and between years) and in the short to medium term is more important than the grazing system used.  However, under moderate to heavy continuous (or set) stocking, palatable grazing-susceptible species are likely to be lost.  Resting pastures at critical times of the year may reduce this deleterious effect, but to aid desirable species the rests need to be timed to the growth of the plants and not on a set time basis.  While rotational grazing may reduce grazing selectivity and provide rests for plants, the required fencing and stock movement may not always be practical or cost effective.

Overstocking is one of the major causes of native pasture degradation.  When perennial grasses are grazed short, the leaf area is reduced and plants need to rely on energy stores to regrow.  The heavier plants are grazed, the more that leaf area and energy stores are reduced.  As plants increasingly rely on energy stores to regrow, the recovery time needed between grazing increases and overall production declines.

Rundown of energy stores due to frequent heavy grazing either directly leads to the death of perennial grasses or weakens them, making them more susceptible to stress.  Hence, adequate rests are needed after grazing, especially where reserves may be low or plants are relying heavily on energy reserves (e.g. during and after drought, fire, heavy grazing or coming out of seasonal dormancy).

Conversely, not grazing or only lightly stocking perennial grasses allows them to become rank and unpalatable, reducing their grazing value.

Fertilisation of native pastures is generally less economic than for introduced pastures, as: many native species have a poorer response to increased fertility; some species will decline with elevated fertility; and native pastures mostly grow on poorer soils.  However, many native pastures need to be modified by farmers for their business to remain economically viable.  There is much data showing that carrying capacities and livestock performance can be greatly improved with legumes plus fertiliser.  This is particularly true where C4 species dominate, as the feed value and growth in winter is greatly improved.  The trick with modification of native pastures for improved production is to maintain natives for stability & year round production & to make the changes gradually over many years to allow for evolution & adaptation of the native system.  Where the change is not properly managed, annual grasses and weeds can become dominant, resulting in a loss of perennial ground cover.  Even where well managed, the addition of fertilisers to highly biodiverse native pastures will lead to a loss of biodiversity.  These factors need to be weighed up before undertaking a fertiliser program.

Each perennial grass species has its own pattern of seeding, germination and growth and will respond differently to the timing and length of rests, height of grazing, fertiliser, competition and shading.  While it isn’t possible to know the characteristics of every species in a diverse native pasture, understanding the differences of the more common species allows managers to maintain or improve the composition of their pasture by making informed choices of how and when to graze, rest and fertilise pastures to favour desirable species over undesirable species.