Preparation of a seedbed to ensure good seed soil contact was always an important element in successful crop establishment. Minimum and no-till crop production systems have, however, proved that a fine tilth for a seedbed is not so critical.
Advances in equipment for minimum and no-till systems has incorporated sowing implements with tynes and press wheels that create furrows. The furrow harvests water into the seed row and the press wheels ensure good seed soil contact.
The use of disc seeding systems is increasing, which leaves the soil surface essentially undisturbed.
Sowing wheat
Seasonal variability always modifies a calendar decision, but whether the season ‘breaks’ early or late, farmers need to be prepared.
Every year there is a weather limit on the window of opportunity for sowing. Sowing requisites and equipment need to be ready to exploit that window.
A season which ‘breaks’ in April is ideal because of the opportunity to use all options. They also provide the best weed control.
Long season (winter) wheat varieties are sown first in April then mid-season varieties follow in May and early maturing varieties in June.
If the ‘break’ is later, long season varieties are dropped out for mid and early maturing varieties.
Many farmers have demonstrated the benefit of sowing a portion of the crop dry if a seasonal break has not been received by late April.
These crops germinate rapidly when rain falls and generally make the best use of limited growing season rainfall.
Depth of sowing
Deep sowing may delay or stifle emergence, while shallow sowing risks seed damage from herbicide uptake.
The length of the first shoot (coleoptile) has a bearing on depth of sowing. If a variety is sown deeper than the natural growth extension of the coleoptile then the seedling may not emerge.
Most current varieties are derived from so called semi-dwarf lines which have shorter stems and shorter coleoptiles than older varieties.
Seasonal differences in depth and availability of moisture influence decisions about depth of sowing.
A sowing depth between 25mm and 50mm, depending on soil type and available moisture, is a useful guide to sensible seed placement.
In moist conditions shallower may encourage faster emergence and crop establishment.
Seeding rate
To achieve total ground cover and establish the foundation for maximum yield, a crop density of 150 to 200 plants per square metre is needed.
This equates to a seeding rate of about 60kg per hectare in lower rainfall zones (up to 400mm annual rainfall) and about 80 to 90kg per hectare in the higher rainfall zones.
Sowing rate can be calculated by knowing the seed weight, germination percentage and required plant density.
The source of seed is very important. Most farmers grow and store their own seed for use in the following year.
However, when introducing a new variety or extra seed, it is sensible to source the best quality seed.
If certified seed is not available, a thorough inspection for insects, weed seeds or mixed grains prior to purchase is the obvious precaution.
Seed dressings
Seed dressings for the control of smuts and bunts should be applied to all wheat seed prior to sowing.
Although major losses from these diseases are now rare, this is due to the routine use of seed treatments.
Seed not treated prior to sowing may result in yield losses as high as 85 per cent.
Some seed dressings can also suppress a selection of wind- or stubble-borne diseases, however some chemicals can reduce coleoptile length.
For more information, go to the Agriculture Victoria website.
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