MOST of the Australian cropping belt has always been regarded as existing in a variable climate where it can be too dry or too wet for long periods, including for vital operations such as sowing.
Increasing the feasible sowing window length, especially at the earlier sowing end, increases sowing options and the reliability of payable crops even in difficult years. Current research suggests sowing early is not too risky as to be dismissed.
There are factors to be addressed to allow earlier sowing of the winter crop, including variety choice, sowing equipment, ensuring subsoil moisture is retained as close as possible to the soil surface, rotations and ability to sow quickly should an opportunity occur.
A number of genetic factors are important for early sown varieties that allow them to mature slower than those sown at traditional times, so as to avoid flowering too early and being severely frosted. “Winter habit” or “vernalisation requirement” results in plants developing slowly until after sufficient time of cold temperatures, generally between 0.0 and 12 degrees. An example is Wedgetail and Kittyhawk wheat varieties.
Photoperiod sensitive (plants develop slowly until exposed to a given duration of day length) and thermal time responsiveness (plants speed up as temperatures increase) also feature in varieties suited to earlier sowing.
How early to sow winter crops, given suitable variety type, is very much temperature related. Documentation is sketchy but tends to revolve around mean temperature of about 23C. For many NSW areas this means early March onwards (common sowing time for dual-purpose cereals) but with big seasonal variability can mean a week or two earlier or later.
Many issues – weed and disease control – are different for early crops. Summer weeds, especially annual grasses, can be an issue because they can germinate with an early sown winter crop, a problem when trying to clean them up, as well as competition for moisture and nutrients. Also there is no opportunity to get a good kill of winter weeds like barley grass, ryegrass vulpia or brome before sowing. Yet, early sown winter crops commonly get a good start on winter weeds. As close as feasible rows, strong growing crops (for example high soil fertility), maybe higher sowing rates, big seeds, all play an important role in early sown crops being more weed competitive. Rotations before early sowing is also important for keeping weed soil seed banks low.
Diseases like crown rot and “take all” can also be a greater risk in earlier sown crops. Previous crops sequences in a rotation are important control aspects. Good stripe rust resistance in wheat varieties is important.
There are management issues with early sowing, yet high yields are more than possible including the option for mixed farmers to gain valuable winter grazing with minimal downside to grain yield. Of paramount importance is if an early sowing opportunity is missed the next one may be months away because of an extended dry period or if conditions become excessively wet.
Next week. Check pastures for legume content and plan to overcome any deficiencies.