Winter cereal growers in the higher yielding environments of the northern region may be sacrificing valuable yield potential for operational efficiencies by sowing on wider row spacings.
Grains Research and Development Corporation (GRDC) funded research suggests that the yield cost could be significant in areas where grain yields over 3.5 tonnes per hectare are expected – as much as 1.0 t/ha yield loss on 50cm rows compared to 30cm rows.
That yield loss represents a substantial cost to an operation’s bottom line and should be carefully weighed up against the operational efficiencies gained through sowing on wider rows.
The widespread adoption of minimum and zero tillage farming systems in the north has been a driving force behind the practice of widening row spacings which enable some growers to better handle stubble loads, reduce machinery and planting costs, and maximise soil water infiltration and storage.
What needs to be calculated is whether the cost reductions and farm management benefits of sowing on wider row spacings sufficiently offset the potential yield loss.
The other compromise of wider row spacings that needs to be factored in is reduced weed competition.
Wider row spacings reduce the crop’s ability to close the canopy and compete with weeds between rows which delays inter-row weed suppression – the wider the rows the longer the delay.
Row spacing is a particularly useful tool in maximising crop competition against weeds. Maximising crop competition helps to minimise the seed set of weeds, which in turn helps drive down the weed seed bank and decrease the rate of developing herbicide resistance.
Herbicide resistance is a rapidly escalating issue in the northern region with weeds such as wild oats, annual ryegrass, awnless barnyard grass, liverseed grass and common sowthistle already having confirmed resistance status. In all of these species, resistance is to one or more chemical groups. Needless to say, managing herbicide resistance is a key element of all good integrated farm management plans.
The most appropriate row spacing ends up being a delicate balancing act between crop yield, ease of stubble handling, optimising travel speed, managing weed competition and soil throw and achieving effective use of pre-emergent herbicides.
Although row spacing is relatively simple to change, the effect on the whole farm system can be complex and can influence grain yield, timeliness of sowing, machinery choice, residual herbicide choice, seed and fertiliser costs, weed management, development of herbicide resistance, and the configuration of other crops sown within the farming system.
Taking a `narrow as possible’ approach when it comes to sowing cereal crops should help ensure that delicate balance is found, enabling growers to preserve yield and manage weeds while sowing unimpeded through stubble loads.
Robert Weinthal, Director/Principal Agronomist
0427 230 427
Sarah Jeffrey, Senior Consultant Cox Inall Communications