Seed spacing history’s full turn
Ability to seed through heavy stubble loads has been the driving force behind the choice of row spacing for the Horwood family at Mingenew.
Peter and his wife Belinda confess to being among the last in their district to switch from combine seed drills to an airseeder bar, having previously weighted their enterprise mix more towards livestock than cropping.
But a move to expand cropping area and boost crop productivity on their 3400-hectare property, ‘Lockier River’, in recent years has led to a fine-tuning of production methods.
“When we switched to an airseeder, we decided to use 25-centimetre spacings with the wheels outside the frame,” Peter says.
“We did think about using narrower spacings, but our adviser warned there was a risk of chemical damage – especially from trifluralin – and that we could have problems getting through stubble.
“In hindsight, we could have gone for narrower spacings.”
Peter says instead of changing seeding machinery, he has been experimenting with ribbon and paired sowing systems on his existing bar.
Ribbon sowing involves planting seed evenly across an entire band (ribbon), usually 50 to 100 millimetres wide. Paired row sowing uses a single seeding boot that creates paired crop rows (usually 75 to 100mm apart).
“On 25cm row spacings, these modifications can ribbon or split-system sow to 8cm and 18cm wide,” he says.
“This most likely produces results similar to a seeder set up with single rows at 12 to 15cm spacings.”
Peter says row-spacing decisions need to be based on the practicalities of handling stubble.
But he is converting to the idea that narrower row spacings will lead to higher crop yields and better crop competition with weeds.
“In the GRDC–Department of Agriculture and Food, Western Australia (DAFWA) trial on our property last year you could clearly see big, bulky ryegrass plants and daylight down the rows in the wide (30.5cm) row spacing plots,” he says.
“There was significantly less ryegrass in the narrow row plots, and what was there produced less seed.
“Even at the lowest seeding rate of 60 kilograms per hectare, crops in the 15cm and narrow paired row spacing plots were a lot thicker than those in the plots with the highest seeding rate of 120kg/ha in the 30.5cm spacing plots.
“Past research has proven that switching to narrower row spacings will boost crop competition, reduce weed seed-set and lift yields – they are foregone conclusions.”
Peter says his future machinery decisions will be based on reducing row spacing widths.
In the meantime, he says there are economical ways to modify existing seeder bars to narrow the row space, including using wider press wheels and spreading seed out in ribbons or in paired rows to achieve the same effect.
Peter says row spacing is one part of his total cropping package that focuses on optimising soil health and plant nutrition.
“If you get the basics right, your crops will out-compete weeds and you will have an integrated weed-control system,” he says.
“Narrow row spacing is really an old technology, but it is a simple tool that can reap great benefits.
“Our grandfathers used 18cm spacings on their old combines and there must have been a reason for it.
“In recent years we have pushed spacings wider to handle stubble and reduce machinery costs, but the wheel is starting to turn back again.”
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The ability to seed through heavy stubble loads has been the driving force behind the choice of row spacing for the Horwood family at Mingenew. Watch this YouTube video for more information: www.grdc.com.au/GC109V-SeedSpacing
GRDC Project Code PLN00008