Sowing depth is critical for tropical grasses and needs to be checked.

Although recent rain has been variable in northern NSW, there are areas with good subsoil moisture and excellent prospects for establishing tropical grasses.

NSW Department of Primary Industries (DPI) District Agronomist at Inverell, Bob McGufficke, said tropical grasses could be successfully established from October to early February providing there was a good reserve of subsoil moisture.

"Summer weeds, in particular annual summer grasses, should have been prevented from seeding for the past two seasons in areas to be sown with tropical grass, as competition from annual weeds (particularly grasses) is a major reason for establishment failure," he said.

A range of tropical grass species is available, and Mr McGufficke said it was important to select the most suitable species for the environment and soil type.

This information is available from NSW DPI.

A range of equipment is used for sowing tropical grasses. Conventional sowing and direct drilling with press wheels are both reliable provided seed is not sown deeper than one centimetre as these grasses are very sensitive to sowing depth.

Air seeders should be fitted with diffusers to minimise seed bounce with the small seeds for more accurate seeding depth.

Surface sown seed should be treated with an insecticide to prevent ant theft and pressing the surface sown seed into loose topsoil can greatly enhance germination.

Adequate seed should be sown to ensure a plant population of 10 plants per square metre.

On red soils, it is estimated that 17 live seeds need to be sown to establish one plant per square metre.

"Heavy soils can be more difficult," Mr McGufficke said.

"If seed is coated, check you are sowing adequate seed to compensate for the weight of the seed coating, which can be much more than the weight of the seed.

"It is important to always obtain a recent seed test for germination, purity and the presence of noxious and other weeds."

Most tropical grasses have low seedling vigour and therefore adequate nutrition is vital to successful establishment.

Phosphorus, sulphur and nitrogen (10-15 kilograms per hectare of N) may be needed on low to moderate fertility soils.

Tropical grasses should be grown with a suitable legume to provide adequate soil nitrogen for grass growth and quality.

Perennial tropical grasses are not usually grazed in the year of establishment until they have seeded.

Under good growing conditions, grazing can increase tiller development.

"It is important to ensure an adequate establishment, as the most expensive pasture is the one that fails to establish properly," Mr McGufficke said.

Contact Bob McGufficke, Inverell, (02) 6722 1388, bob.mcgufficke@dpi.nsw.gov.au