Pasture for traprock, sandstone and dry granite country

A pasture plant namely clover

Subterranean clover is well adapted to the sandy soils of the Granite Belt and the hard setting gravelly soils of the traprock country of southern inland Queensland

Pasture requiring less than 700 mm rainfall can be grown in the dry granite, sandstone and traprock soils which retain little moisture.

Soils

These traprock, granite and sandstone soils retain little moisture. Some soils derived from traprock have hard setting surfaces. Granite soils are acid (usually below pH 5.7). Acid sandstone in the Leyburn area is usually indentified by bulloak and cypress pine trees.

Pasture productivity

Grass production on these soil types is generally restricted to summer-growing species. The quality during the growing season is adequate for animal production but during the winter, animal production can be severely limited. The inclusion of winter-growing legume in pasture sowings can assist in supplying some of the protein required for livestock production.

More than half of the area has topography unsuitable for commercial sown pastures. Establishing pasture on degraded soils can be expensive and unrewarding unless soil fertility and organic matter are improved with fertiliser and crop residues. In suitable areas, good sown pasture can give a two to three-fold increase in carrying capacity over native pasture.

Potential productivity depends on soil moisture storage. The deeper permeable traprock and fine-textured granite and sandstone soils in the higher rainfall zones are the better soils and are most likely to be improved. The shallow gravelly soils are less productive as they have features like hard setting surfaces and steep slopes that shed rainfall. Coarse sands are the least productive.

Seasonal production

The benefits of improving pastures are in increasing winter production and replacing unproductive native grasses with improved species. Sown-pastures are used to improve winter and spring production. Table 1 shows the seasonal dry matter production for sown and native pasture.

Table 1: Percentage of total production
Season Sown pasture
with winter legume
Native pasture

Spring

26 30

Summer

28 42

Autumn

23 25

Winter

23 3

Pasture species and sowing rates

Sub clover is recommended for all sowings on granite and traprock soils. Serradella is a species well adapted to granite and sandstone soils. Cluster clover and rye grass contribute little in the first few years, but are valuable in the long-term. Additional winter/spring species could include white clover, and rose clover in selected areas. Lucerne grows well on the better traprock soils, but will not persist under very wet conditions.

Table 2: Mixtures (kg/ha)
Winter/spring
species
Hard
setting soils
Acid
granite
Acid
sandstone
Clustered clover 1

½

½

Serradella - 2 2-3
Sub clover 2 2 1
White clover - 1 -
Fescue - 2 -
Ryegrass
(perennial or annual)

½

½

½

Note: Inoculate and lime pellet all legume seed. Pellet serradella with bauxite or ground rock phosphate. Sowing rates given can be increased.

The grass component is usually provided by existing native species, but if these have been cultivated out or depleted by overgrazing leaving undesirable species, sow one or a mixture of the improved grasses from the list below. The variety names of some of the legumes mentioned above are also included in the list below:

  • Digit grass (Premier) for all soil types
  • Rhodes grass (Katambora, Finecut) on sandstone soils but not granite and traprock
  • Forest bluegrass (Swann) for traprock soils
  • Indian bluegrass (Medway) for traprock soils
  • Kikuyu (Common) for granite soils
  • Brunswick grass (Blue Dawn) for granite soils
  • Perennial rye grass for granite soils
  • Annual ryegrass (Wimmera) mainly for traprock soils
  • Lucerne has been grown on traprock soils but will not persist for long under constant grazing or wet conditions
  • Serradella a mixture of Yelini, Santorini, Caharano, and Jebala for granite and sandsone soils
  • Sub clover (Nungari Izmir, Dalkeith, Urana, Seaton Park and York)
  • White clover (numerous varieties)
  • Rose clover (Hykon or Sardi rose) are not very productive but very persistent
  • Biserrula (Casbah and Mauro) is a new species that has shown promise in trials on granite and traprock soils.

Sowing

When to sow

Sow the winter/spring growing mixtures between April and June after the first growth of native grasses has slowed.

Where summer grasses are to be included, sow the winter-growing annual legumes between April and June and sow the summer grasses and lucerne in the following spring/summer. An alternative is to undersow the annual legumes under oats in autumn and sow the grass into the stubble in spring or summer.

How to sow

Prepared seedbed

Cultivate early enough to prepare a seedbed and store some water. Seed may be broadcast onto the dry seedbed surface, or drilled shallow into the dry seedbed with precision planters fitted with presswheels. Small seeds should not be covered by more than 5-10 mm of soil.

Seed-soil contact may be improved on non-crusting soils by rollers or presswheels that will firm the seedbed soil around the seed. Be careful if harrowing after sowing that the small pasture seed is not being buried by more than 5-10 mm of soil or the shoot might not have the energy to emerge and establish.

Oversowing (aircraft or ground spread)

Oversowing is seldom successful in this area unless conditions are favourable, with good soil moisture and a good cover of dry grass. Use only the annual winter legumes and white clover, inoculated and lime pelleted. Do not oversow the hard setting soils.

Direct drill

Drill legumes to a depth of 5-10 mm in autumn, and use presswheels to consolidate the row. Small seed should not be covered by more than 10 mm of soil. Direct drilling has a greater probability of success when carried out in a wet autumn.

Fertiliser

Superphosphate is recommended for all pastures applied before or at sowing.

Table 3: Superphosphate application
Soil test phosphorus
(mg/kg)
Superphosphate
rate (kg/ha)
Below 7 300
7-12 250
12-17 200
17-22 150
22-30 100

Molybdenum is applied at sowing, as Mo 200 superphosphate at 250 kg/ha, or added to seed-pelleting lime at 130 g of molybdenum trioxide per ha.

Management of new pastures

Graze leniently in the first season. Grasses need to have secondary roots and preferably have set seed before grazing.

It is important to allow annual legumes to set seed in the first year. Some grazing can be applied during the growth period. While plants are flowering and setting seed they should be locked up or the grazing pressure reduced.

General information

Cover crops

A winter cereal may protect young pasture plants from frost but more often competes strongly with the pasture. If used sow at about one third its normal rate (i.e. 10-12 kg/ha). Sowing depth, sowing time and grazing management should be considered in relation to the pasture, not the cover crop. A cereal cover crop can provide useful feed while waiting for the pasture to become productive.

Annual grazing crops (winter)

Where these grazing crops are used, a legume component should always be sown with them. Woolly pod vetch (2-3 kg/ha) is suited to all soils under cultivation, and can be sown at the same time and depth as the grazing crop. Annual winter pasture species should not be sown until mid-March and then at a shallower depth than the cereal seed.