Formerly Queensland Government
Land condition determines the capacity of grazing land to produce useful forage.
It is a measure of how well the grazing land ecosystem is working:
- how well sunlight is being captured and converted into feed,
- how well nutrients are being cycled, and
- how well rainfall is being used to grow grass.
Land condition is therefore directly related to carrying capacity, livestock production and profitability of a grazing enterprise.
What is land condition?
Land condition is a relative and arbitrary measure of the health of grazing lands. It has three components, all of which can be assessed, measured and monitored:
- soil condition
- pasture condition
- woodland condition.
Soil condition determines the capacity of the soil to absorb and store rainfall, to store and cycle nutrients, to provide habitat for seed germination and plant growth, and to resist erosion.
Pasture condition determines the capacity of the pasture to capture sunlight and convert its energy into palatable green leaf, to use rainfall efficiently, to conserve soil condition and to cycle nutrients.
Woodland condition determines the capacity of the woodland to grow pasture, to cycle nutrients, and to regulate ground-water.
Indicators of land condition
High presence of organic matter and good soil structure are key indicators of soil condition. Compare the soil surface condition around a grass tussock to that in a bare or scalded area.
Erosion is another key indicator of soil condition. Signs vary with the form of erosion. Inter-rill or sheet erosion is the loss of thin layers or sheets of soil in each successive storm and can eventually lead to the loss of all top-soil. As water concentrates into discrete flow paths, it forms rill erosion, seen as tiny gullies. As these rills widen and deepen, they form gully erosion.
Scalding is the result of massive loss of top-soil in texture-contrast or duplex soils. The sub-soil, when exposed, is typically hard when dry and has very low infiltration rates.
The density and coverage of 3P grasses (perennial, productive, palatable) is a key indicator of pasture condition. 3P grasses capture sunlight efficiently and help keep moisture and nutrients in the paddock. They maintain soil organic matter, thereby stimulating soil organisms and promoting soil structure. Decline in 3P grasses reduces land condition.
Maintaining ground cover above 50% is essential for minimising run-off and loss of nutrients and soil. Low ground cover results in less sunlight being used by plants and poor water use.
Weeds compete with the desirable pasture plants for light, nutrients and water. Some weeds also hinder stock movement and others may be toxic to cattle. Weed infestations are often associated with declining land condition, as weeds are able to exploit disturbed and bare areas, taking advantage of reduced competition from pasture.
Woody plants use resources that could otherwise be directed towards forage production. Increased woodiness therefore reduces carrying capacity. Many grazing lands have a trend of increasing woodiness associated with lack of fire. Woody plants can stimulate the ecosystem by acting as nutrient pumps and reducing water loss via evaporation. However as the density of woody plants increases, the competitive effects on pasture growth usually cancel out the stimulatory effects.
Classifying land condition
Land condition can be classified into four broad categories:
Figure 1. Land in ‘A’, or good, condition
Good or A condition (Figure 1) has all the following features:
- Good coverage of perennial grasses dominated by those species considered to be 3P grasses for that land type; little bare ground (less than 30%)
- Few weeds and no significant infestations
- Good soil condition: no erosion, good surface condition
- No sign, or only early signs, of woodland thickening.
Figure 2. Land in ‘B’, or fair, condition
Fair or B condition (Figure 2) has at least one or more of the following features, but otherwise is similar to A condition:
- Some decline of 3P grasses; increase in other species (less favoured grasses, weeds) and/or bare ground (more than 30% but less than 60%)
- Some decline in soil condition; some signs of previous erosion and/or current susceptibility to erosion is a concern
- Some thickening in density of woody plants
Figure 3. Land in ‘C’, or poor, condition
Poor or C condition (Figure 3) has one or more of the following features, but otherwise is similar to B condition:
- General decline of 3P grasses; large amounts of less favoured species and/or bare ground (more than 60%)
- Obvious signs of past erosion and/or current susceptibility to erosion is high
- General thickening in density of woody plants.
Figure 4. Land in ‘D’, or very poor, condition
Very poor or D condition (Figure 4) has one or more of the following features:
- General lack of any perennial grasses or forbs
- Severe erosion or scalding, resulting in hostile environment for plant growth
- Thickets of woody plants cover most of area.
On any land type, each of the condition categories may be represented by more than one form or ‘state’. For example, condition A land may be represented by different mixes of 3P grasses (including exotics). Similarly, condition D land may be represented by lack of 3P grasses, or by a high density of woody plants, or by extensive loss of soil condition. The four broad condition categories provide a means of ranking these ‘states’ with respect to their ability to grow useful forage.
Land condition can change due to natural events (e.g. drought) or due to grazing land management practices (e.g. stocking rates, fire, weeds) of the landholder. Degradation of grazing lands is the loss of land condition. In the early stages of degradation, the condition of the land is responsive to a change in management. Degradation is judged to be severe if it is irreversible over a reasonable time scale and/or is expensive to rehabilitate. The rolling ball model demonstrates these principles.