Annual pastures are those that germinate at the break of the season. They grow, flower, set seed and then die off during late spring.
Once sown, annual pastures should not require any further re-seeding for many years if managed correctly.
Perennial pastures are those that generally remain alive and green all year round such as couch, kikuyu, Rhodes grass, lucerne and strawberry clover.
The balance of winter and summer growth varies between species and is influenced by the availability of summer moisture.
Perennial pastures generally require rotational grazing and higher management input as they are inclined to thin out over time.
It is best to mix annual and perennial species that have different growth habits and resistance to insects. A suitable mix may include three legumes and two grasses.
It is possible to have a thriving winter annual pasture and a productive summer perennial pasture in the same paddock.
It is a good idea to seek specific advice on the selection of varieties once you have established your land management types and other environmental conditions.
Subterranean clover is typically the dominant legume for all pasture mixes on mildly acidic sandy loam and loam soils. Recommended varieties and their features can be found on our Subterranean clover page.
Other annual clover varieties include Paradana balansa clover, Nitro-plus Persian clover, Cefalu arrowleaf clover, crimson clover and Hykon rose clover.
Your choice will depend on the characteristics of your block, including rainfall reliability, soil texture, your proposed grazing management and the incidence of insects and disease.
Several annual legume varieties may be used together to give variable growing times and to increase the probability that at least one will persist in difficult conditions.
Two other types of annual legumes, serradella and medic, may be added for specific soil types and climatic conditions.
Serradella such as French serradella and yellow serradella will survive on more acidic and sandier soils where other annual legumes and medics tend to perform poorly.
Medics are more suited to heavy loam soils, but are very susceptible to low pH (acidic) soils.
If you are growing a legume species for the first time, it will need to be inoculated with an appropriate soil bacterium (rhizobia); this is required so the plants properly fix nitrogen (N) when growing.
Just before planting, seed is coated with inoculant that comes in small bags of peat (be sure to match the right strain of rhizobia for the variety).
Lime is then added to the seed to provide the rhizobia with an alkaline environment when the seed is planted.
It is important to use agricultural lime — slaked or hydrated lime is too alkaline and will kill the rhizobia. Dry granular inoculant is now an alternative and comes in a vermiculite or clay based granule that is mixed with the seed.
There is a large range of annual ryegrasses and new varieties appear each year. Dargo, Rocket, Tetila Gold, Pronto, Safeguard, Surrey, Adrenalin, Concord and others all have their different advantages.
Be aware that annual ryegrass toxicity (ARGT), can be a livestock health problem associated with some annual ryegrasses - long season ryegrass types are less troublesome than others.
Palestine strawberry clover is the main perennial clover used on non-irrigated pasture. It requires permanently moist soils, yet tolerates drought and mildly saline conditions and prefers a near neutral soil pH.
Lucerne maybe an option in some situations, particularly where there is access to irrigation over summer.
Winter active/summer dormant perennial grasses include perennial ryegrass, phalaris, cocksfoot and tall fescue.
They are well suited to land south of a line between Busselton, Lake Muir, Mt Barker and Cape Riche in Western Australia.
Cocksfoot and phalaris are the most drought tolerant, however phalaris can be toxic — especially if grown as a dominant species. Giving animals a mix of pasture is always safer.
Sub-tropical grasses tend to be more active in spring and summer and have less tolerance of frost.
Rhodes grass is generally recommended as it has excellent spreading capability. Varieties include Callide, Finecut, Topcut and Katambora.
Kikuyu, couch, paspalum and Gatton panic are other perennial sub-tropical grasses in use. Kikuyu can be invasive in summer moist areas like creeklines.
Heavy winter rainfall and over–watering irrigated pastures can cause the loss of the phosphorus (P), sulphur (S), potassium (K) and nitrogen (N) that has been applied, or accumulated, in the soil.
Be aware of the environmental issues associated with fertiliser application.
The lost nutrients may be leached into water bodies, contributing to eutrophication and algal blooms. Best management practices to reduce the leaching of nutrients to water bodies are necessary.
An essential element of any best management practice is soil testing. Strategies to reduce leaching:
- Measure the area to be fertilised. Do not include non-productive areas, firebreaks, laneways and waterways.
- Apply the nutrients needed. Soil tests are the best guide to determine the P, N, K and S status and hence fertiliser required.
- Apply nutrients at a strategic time. To avoid leaching of major nutrients apply them at the best time to enhance plant uptake. If the nutrients are applied only once, application at 3–4 weeks after germination is the best time for both pasture and the environment.
- Use a slow release fertiliser source on sandy soils.
The optimum soil pH is 5.5- 6.5 measured in water; landowners should soil test to identify if soil pH is below this level and requires action (generally the application of lime).
As a landuser you need to be constantly vigilant when it comes to weeds and their control. Ensure that:
- You know and recognise your weeds.
- A quarantine paddock should be used for all stock entering or returning to the property, to allow time for disease and weed seed isolation to occur. Stock will only need to be isolated for a few days. It is better to concentrate any new weeds in one paddock than all over the farm.
- Rubber tyres and footwear are cleaned of seeds before coming on-farm from other properties and off-farm events.
- Grazing is managed so that it does not result in bare patches, which are prone to weed invasion. Regularly inspect your property for weeds and control them promptly.
- When using any chemicals follow the label instructions and safety procedures.
- Stock are checked for seeds and seeds removed before being transported to the property.
The number of stock a pasture can support without becoming overgrazed and degraded is called its ‘carrying capacity’.
Carrying capacity is expressed as the number of adult dry sheep equivalents (DSE) that can be grazed on a year round basis on the land without soil degradation, and with only minimal hand feeding in the late summer/autumn period.
With the right number of grazing animals on a pasture they will remain healthy and the soil will not become bare at the end of summer/autumn.
Many small landholders, particularly horse owners, are surprised at how few animals can be run per hectare without serious damage to the property.
Sprinkler irrigated pastures play an important role on many holdings as an all-year-round source of feed. Close attention to the establishment of pastures and their subsequent watering, fertiliser and grazing management is needed to ensure success.
Water quality for irrigating pastures should have a low salt content. Less than 135 milliseimens per metre (mSm) for clover or up to 450mSm for kikuyu, some reduction in yield will be experienced with higher salt levels.
Large volumes of water are required for irrigation.
From November to the end of February, sprinkler irrigated pastures require up to 600 cubic metres (m3) of water per hectare per week; that is, a 60 millimetre (mm) depth of water per week over the whole area. Outside these months, the requirement drops to about 375m3 of water per hectare per week.
Correct irrigation scheduling is necessary to ensure optimum irrigation efficiency and to reduce leaching of nutrients.
As a guide, pastures need irrigating once a week in cool weather and, in hot weather, twice a week on loam soils and at least three times a week for clover-dominated pastures on sandy soils.
Soil moisture monitoring is good to include for irrigation scheduling.
Determining the best pasture for your needs requires a holistic stocktake of your operation including the livestock you intend to carry, climatic conditions, soil type, potential weed problems and the topography and layout of the land.
An understanding of how these factors work in combination will go a long way to helping you make an informed pasture choice.