Settings help weed control in zero-till system

Types of machinery and how graingrowers use them can make a difference in controlling weeds in a zero-till farming system.

A research project run by the Birchip Cropping Group (BCG), 10 kilometres south-east of Hopetoun in Victoria"s southern Mallee, is using different zero-till seeders at the same time as testing the effectiveness of different group D herbicides in controlling weeds.

The project is on trial plots sown to "Yitpi"Variety protected under the Plant Breeders Rights Act 1994 wheat last May on a paddock with retained canola stubble. Before sowing, researchers spray-painted a two metres by 0.5m area of each plot either pink or white to allow visual assessment of the amount, depth and distance of soil throw between tynes. Each machine worked plots at 8kmh and 11kmh.

Best early results in crop germination and weed control are from a plot sown by a Janke bar on a 22-centimetre row spacing worked at 8kmh. This produced 100 percent soil cover across inter-rows and 1cm soil depth in the inter-row. Soil cover between the inter-rows is essential to lock in the group D herbicides used in the experiment.

A Janke bar on 35cm spacing did not perform as well, with 80 percent inter-row soil cover and 1.5cm gaps in the middle with no soil cover. A Gason seeder on 25cm tyne spacing achieved 95 percent or 60 percent inter-row soil cover, depending on sowing speed, and uneven soil distribution in the inter-row. A Daybreak disc seeder on 45 percent spacing achieved 50 percent or 30 percent inter-row soil cover and large gaps of up to 25cm in the middle of the inter-row with no soil cover.

BCG consulting agronomist Harm van Rees believes the results show that press wheels suit the area"s sandy loam soil in improving seed and soil placement. At a recent GRDC update at Hopetoun, he said the narrower spacing provides more soil coverage, helping to suppress weeds. Plots were treated with Stomp Xtra, Stomp, TriflurX, Duet, or no chemical as control. Early weed seed counts show that Duet is not performing as well as its fellow group D herbicides.

GRDC Research Code: BWD00008.

For more information: Harm van Rees, 03 5439 3089,

PBR Varieties displaying this symbol beside them are protected under the Plant Breeders Rights Act 1994.

Region North, South, West