Establishing sown pastures
We do not recommend replacing productive native pastures of black speargrass, Queensland bluegrass or forest bluegrass unless they have been overtaken by unpalatable species (such as wiregrass).
Sown pastures have the potential to improve stock production in many areas of the Burnett. Introduced grasses and legumes can rejuvenate run-down native pastures and old cultivation country.
We do not recommend replacing productive native pastures of black speargrass, Queensland bluegrass or forest bluegrass unless they have been overtaken by unpalatable species (such as wiregrass). Careful management of native pasture provides the cheapest long-term fodder source for stock. The addition of a tropical legume may be all that is needed to give native pasture a worthwhile boost (see Enhancing native pastures ). New sown pastures will be the most productive for the first 3-5 years. After this, there is usually a tie-up of nitrogen in the soil and production decreases. To maintain production levels fertiliser, scarifying and adding a legume will be required. The rules of thumb for establishing sown improved pastures are:
- Better seedbeds mean better establishment.
- Sow most grass and small legume seeds on the surface.
- Sow when there is good soil moisture at depth.
- Know the quality of the seed before planting.
Selecting pasture mix
The mix of grasses and legumes planted depends on the soil or land type and on the cost and availability of seed. See Pastures for detailed information about grazing land types and species descriptions to help select suitable species. Preparation time and planning is important. It is best to plan up to 12 months in advance for a pasture planting program.
When to plant is the most difficult decision in establishing pastures. It is always hot and dry after you plant! Plant summer pastures from August to March. Early or late is the best option. Early rain in September will be useful for germination and establishment, while rain may fall more reliably in January-February. Hot, dry spells from October to December often kill young seedlings. April-May is the preferred time for temperate species such as lucerne, medics, clovers and vetches. Grass weeds, particularly in old cropping ground, can cause establishment failures. Sometimes the pasture will not be at its best until the second year. Weeds are generally worse in spring plantings. Delaying planting until January-February is often worthwhile, but do not leave it so late that short new pasture is frosted. Pasture seeds are usually planted dry and will be dormant until the next rain. The seed zone needs to be moist for 3-4 days for germination to occur. Along with surface moisture, pasture establishment relies on deeper, sub-soil moisture.
Cover crops have been widely used to establish pastures in the Burnett. Cover cropping involves planting crops such as maize, oats, grain sorghum, forage sorghum and millets at half their normal seeding rates.
There are four reasons given to justify the use of cover crops:
- shading to protect young seedlings on sandy soils
- suppressing weeds
- providing grazing or some cash return if the pasture fails
- reducing erosion on steep country.
Of these reasons, only minimising erosion is valid. Planting in early spring or autumn will avoid seedlings being burnt in sandy soils. Planting a cover crop thick enough to suppress weeds also suppresses the pasture. A cover crop is often grazed before the pasture has fully established. Successful pasture establishment using cover crops occurs only in good seasons. Often the cover crop will compete for moisture with the pasture, inhibiting its growth and establishment.
Seedlings need some soil disturbance to establish. Few legumes and almost no grasses will establish in undisturbed soils, especially those with hard-setting surfaces. Failure of sown pastures is often due to poor seedbed preparation, so give yourself enough time to prepare a suitable seedbed. If preparation is left too late the result is often a rough, cloddy seedbed, poor weed control and little sub-soil moisture. Prepare a firm seedbed for small pasture seeds. Avoid over-cultivation of soils that are prone to setting hard or crusting after rain. These soils include many Inland Burnett forest soils and some old cultivation soils that are often poorly structured and have a tendency to surface seal. Seedbed preparation does leave soils prone to erosion. Try to follow these guidelines to reduce soil loss:
- Do not cultivate in gullies and drainage lines.
- Divert run-off water away from the cultivated ground.
- Leave grass strips in ploughed areas.
- Avoid overworking soils to produce a very fine, powdery seedbed.
The planting method chosen depends on the seed type and machinery available. Often a local neighbour with good pastures has the best experience for your local area.
Seed can be spread using a rolling drum seeder, fertiliser spinner or combine drill with the seed hoses removed. Other options are full cultivation, sod-seeding, bandseeding and using a crocodile seeder. Adding a legume during pasture cropping can also have some success (see Enhancing native pastures ).
Planting fluffy seeds
Fluffy seeds, such as Rhodes grass and creeping bluegrass, are hard to spread with some planters. To make planting easier try mixing the seed with fertiliser, cracked grain or sawdust to act as a carrier. Another option is to purchase coated seed. If mixing with fertiliser, do not leave seed and fertiliser mixed longer than necessary. If the planting mix includes inoculated legume seed, these seeds must be pelleted before mixing with fertiliser. Mixing seed with sieved, dry sawdust is safer than using fertiliser as the carrier. Use twice the volume of sawdust to grass seed. Calibrate the seeder using only sawdust, before adjusting with seed and sawdust. If broadcasting, only fill the hopper with enough seed for 1-2 ha to prevent bridging. Use runs 1.25-1.5 m apart and check how far the seed has thrown. It may be better to plant across the wind.
Many seed companies now offer coated seed. Using coated seed will generally make planting easier and more accurate. The coatings are lime-based and contain various fertilisers. Remember to increase the planting rate to compensate for the increased weight and volume of the coated seed. A kilogram of coated seed contains less seeds/kg. To determine the required rate of coated seed multiply the seed rate in kg/ha by 3.
Coated seed is advantageous if ants are likely to remove or destroy fluffy seeds. The seed coating can have insecticide added to protect the seeds from ant damage. In the case of legumes, the rhizobia inoculant can be added when the seed is coated and will remain viable for 28 days.
Seed is usually placed on the surface and lightly covered with soil. To achieve the best strike with most pasture grasses and legumes do not bury the seed deeper than 10 mm. However, lucerne, purple pigeon grass and silk sorghum can be planted as deep as 25 mm. A small seeds box or a C-seeder mounted on a combine will let you plant at two depths.
Rolling and harrowing
Rolling and/or harrowing will improve emergence on most soils. However, many old cultivation soils are poorly structured and tend to surface seal. Using a roller after planting can make crusting worse.
Harrows on their back or chains and weldmesh will cover seed from 0-10 mm deep, depending how rough the seedbed is. Very loose soils, such as red snuffy soils, may need rolling before and after planting. Rolling with dual tractor wheels has proven very successful on these red soils.
Old cultivation soils often have low fertility. Before investing in pasture improvement it is worth getting a soil test to see if there are any problems. A fertiliser program can then be implemented. Phosphorus, nitrogen and potassium are the main nutrients pastures need. Many red soils in the Burnett are very acidic. These soils will benefit from applications of lime before planting the improved pasture. Lack of nitrogen is a common cause of poor grass growth and low nutritive value, especially on some old cultivated forest soils.
Weeds can be a major problem when establishing pastures. They are usually worse in old cultivation ground. Ways to reduce competition from weeds include:
- Delay planting until January-February to reduce the number of grass weeds.
- Slash to reduce weeds; this will limit their growth and reduce competition for moisture.
- Use herbicides to control grass weeds. Most herbicides will damage young legumes. 2,4-DB, Spinnaker and Broadstrike are recommended in pastures containing lucerne, medics and clovers.
- If broadleaf weeds are a major problem, another option is to plant grasses and then when they are established oversow with legumes. This way broadleaf herbicides can be used in the establishment phase of the grass.
First year management
Grazing management in the first year is critical to the establishment and long-term viability of sown pastures. There are two general approaches:
- no grazing until the pasture seeds
- lightly grazing once or twice during the first summer/autumn.
Light grazing is preferable. It will provide some feed, and encourage the grasses to spread out and reduces the build-up of too much growth that can smother the young grasses and legumes. Heavy grazing will permanently damage the pasture. Allowing the pasture to seed in the first year is important for grasses that reproduce only via seed rather than runners. Rhodes grass and creeping bluegrass will fill in the gaps without seeding. Frosted pasture can be grazed. After spring rain, allow a build-up of feed before grazing. Planning a forage sorghum crop for this time can give pastures a break. More pastures are destroyed in the first year due to overgrazing than for most other reasons. Sown pastures are not indestructible.