Tropicals

Always aim to sow into good subsoil moisture. Ideally, sow seed shallow into firm moist soil. Rain following sowing is critical. Ideally, favourable conditions are needed in the 3-4 weeks following emergence to ensure secondary root development. Rolling, sowing on time and reducing week competition can make better use of available moisture. Use a moisture probe to monitor subsoil moisture in the fallow.

Weed competition is a major cause of pasture failure. However weeds can be controlled prior to sowing. This is why planning is so important.

Get to know the paddocks intended for sowing and the weeds that are likely to establish following sowing. Remember that potential weeds of summer growing pastures may not be significant weeds in winter crops, and that herbicides for use in pastures are few. Annual grasses and broadleaf weeds such as rape, turnip, caltrop and mintweed threaten seedling establishment.

Broadleaf weed herbicides have a role but it is most cost effective to control weeds in the fallow and in crops before sowing. Prevent annual weeds seeding the previous summer. Do not sow in spring unless one good germination of annual weeds in controlled. Observe any plant back periods as per chemical labels.

The quality of tropical grass seed can be extremely variable and often disappointing. Seed dormancy is common. Insist on a recent seed test for purity, viability, germination and weed contamination (germination percentages in the order of 40% for tropical grasses are acceptable while 70% is considered very good). The risk of bringing parthenium weed and other noxious weeds onto your property in low quality seed can result in enormous ongoing expense. Inoculate all companion legumes unless you have good evidence that the correct strain of rhizobia is abundant in the soil.

Seed treatment to prevent seed theft by ants is essential for all surface sown seed. Nutrient seed coating has not shown any advantage except improved physical handling of fluffy seeds. Fungicides are unlikely to give a response except when sowing legumes in cold wet conditions.

A soil test conducted prior to planting should be undertaken to identify any fertility issues. Good nutrition is important as tropical grasses can produce large amounts of drymatter and without adequate nutrition soil nutrient decline will occur more rapidly.

Plants need to be well anchored before grazing. Unless you are trying to bulk up the stand an initial light grazing is encouraged to assist the plants tillering and to assist with weed control.

Once a pasture is established management can be difficult due to large paddock size. For high livestock growth rates, these grasses should be kept leafy and legumes should be kept in the pasture for as long as practical. This ensures grasses remain vigorous and improves the likelihood of nitrogen being available for subsequent crops.

Some producers have found that grazing pastures hard in summer/early autumn to open up the sward enables annual legumes to better regenerate. By grazing a number of paddocks in rotation, say one year in three, legume content may become sufficiently dense to maintain or increase soil nitrogen and promote grass growth.

Perennial grasses in general benefit from being allowed to seed periodically. Spelling the paddock allows root reserves to replenish and provides seed for regeneration.