A survey of paddocks in South Australia, Western Australia, Tasmania and Victoria shows more care may need to be taken when it comes to setting up seeders for sowing.

Dr Glenn McDonald, an associate professor at the University of Adelaide, says the survey of 143 paddocks showed considerable variation in seed placement and crop establishment.

"Crop establishment rates of more than 70 per cent were recorded, but values as low as 30 to 40 per cent were also measured," Dr McDonald says.

"Many crops can compensate for variations in plant numbers, so low establishment may not necessarily lead to lower yields."

Calibration

Dr McDonald says manual air seeder calibration produced poorer establishment results than paddocks in which the calibration was done using the air seeder control system.

However, he says errors can occur, so taking some extra time to ensure the seeder is calibrated correctly may be an important step in achieving good establishment.

Pictured is the variation in emergence and uneven spacing that often occurs with conventional seeders. Photo: Glenn McDonald

The 2018 survey of wheat, canola, faba bean and lentil crops was done with assistance from the Hart Field Site Group, Birchip Cropping Group, Western Australian No-tillage Farmers Association, Southern Farming Systems, Liebe Group, Facey Group, Corrigin Farm Improvement Group and the MacKillop Farm Management Group.

Dr McDonald says some growers were able to achieve high rates of establishment and low seed placement variability, which suggests that improvements to establishment can be achieved with current commercial air seeders.

"Separating seed and fertiliser delivery and sowing in paired rows rather than single rows were associated with improved establishment in a number of crops," he says.

"All growers used press wheels when sowing crops, but most did not know or were unsure of the press wheel pressure used, with the values provided covering a considerable range.

"Seed-to-soil contact is important for effective crop establishment, so growers who do not have sufficient pressure on their press wheels may end up with reduced crop establishment."

Dry sowing

Dr McDonald says dry sowing is widely practiced, but the associated risks are high.

"The current push to sow crops early in the season may inevitably lead to crops being sown more often in marginal conditions, which may reduce crop establishment," he says.

In terms of canola, Dr McDonald says one of the clear findings was that early sowing reduced crop establishment, which was most likely a result of sowing dry into marginal moisture.

"However, lentil establishment was reduced as soil moisture increased, which shows that different crops respond in different ways to a variety of seasonal and soil conditions."

Pictured is the emergence that occurs with a precision planter, which minimises the degree of interplant competition.
Photo: Glenn McDonald

Stubble cover

Apart from time of sowing, Dr McDonald says the other factors important for crop establishment were stubble cover, depth of sowing and sowing speed.

"In faba beans, increased establishment was recorded where the stubble load was high," he says.

"But in canola, the higher the stubble load, the poorer the establishment, which backs research in central New South Wales where similar results were recorded.

"Nonetheless, there are benefits in having stubble cover, so you need to weigh up the risks versus the advantages."

Sowing depth

In terms of sowing depth, Dr McDonald says better establishment was achieved in canola with slightly deeper planting to about 30 millimetres.

"With lentils it was the opposite, resulting in poorer establishment with deeper planting to between 50mm and 60mm.

"In faba beans, sowing at 20mm produced establishment results of just 50 per cent, whereas a sowing depth of 40mm produced establishment results of close to 100 per cent."

Sowing speed

Dr McDonald says the survey also showed sowing speed influenced crop establishment.

"Growers who sowed at eight kilometres an hour achieved more than 80 per cent establishment, whereas those sowing at 10km/h only achieved 50 per cent establishment."

More information: Associate Professor Glenn McDonald, 08 8313 7358, glenn.mcdonald@adelaide.edu.au