Technology enthusiast Roger Todd employed a chaff deck for the first time last year to drive down the population of herbicide-resistant ryegrass on his family’s farm

Roger Todd used a chaff deck on his 7000-hectare family farm for the first time last year. He is hopeful it will drive down the population of herbicide-resistant weed seeds on his property north of Condobolin in central NSW.

Growers: Roger and Fabien Todd Location: Condobolin, NSW Farm size: 7000 hectares (3000ha zero-tillage and controlled-traffic farming; 4000ha mixed farming with agistment cattle) Annual rainfall (long-term mean): 420 millimetres Soil types: sandy red loam Soil pH (calcium chloride): 5.0 to 5.5 Enterprises: cropping and agistment Crops grown: wheat (LongReach Lancer and LongReach Spitfire), chickpeas (Kyabra), barley (La Trobe and RGT Planet), canola (ATR-Gem), oats and forage canola (Bouncer)

Through reading 'GroundCover™' and Twitter he had heard about the benefits of HWSC from Western Australian growers who had adopted the tactic and was keen to investigate the concept further. In August 2017, he and other central west NSW growers, led by his agronomist Chris Baker, travelled to WA and saw first-hand the pros and cons of various forms of HWSC.

Recently, Roger has noticed more ryegrass surviving through to harvest and, in 2017, he felt the time had come to implement harvest weed-seed control (HWSC) to reduce the ryegrass population.

Roger farms 7000ha with his wife Fabien 66 kilometres north of Condobolin, where 420 millimetres of rainfall is the long-term annual mean. They like to maintain as much stubble as possible to maximise water infiltration into their red sandy loam soils.

The 42-year-old hopes any weed seeds placed there will rot over time through compaction when his tractor, airseeder, self-propelled boomspray, urea spreader and harvester travel up and down the permanent and unsown wheel tracks he has had in place for more than a decade.

A new chaff deck is enabling Roger Todd to confine herbicide-resistant ryegrass seeds to wheel tracks on the 3000 hectares of land he runs under controlled-traffic farming in central NSW.

“We noticed a lot of guys were running chaff carts, but I was interested in a chaff deck. It appeared less labour-intensive because the chaff did not require burning,” Roger says.

After visiting Bolgart–Goomalling grower Trevor Syme and Esperance grower Mark Wandel, who both use chaff decks, Roger bought a WA-made chaff deck for $15,000 and had it shipped to his family’s farm.

He sees the system as a cost-effective way to place any ryegrass seeds that have escaped in-season weed control.

“If too many weeds emerge from the tramlines, we will make a shielded sprayer and control them with alternative herbicides,” he says.

During harvest Roger tweeted that the chaff deck was “working a treat”. He was asked if there were any adverse impacts on harvesting and replied that there was no additional dust build-up and the power requirement did not seem any different because the chaff deck is plumbed into the hydraulics.

When GroundCoverTM spoke to Roger, he said the chaff deck did the job but a shaft broke about halfway through harvest, requiring the manufacturer to send a replacement part from WA.

“Not much wheat was done, but it worked well on the barley, chickpea and canola,” he says.

Normally, Roger harvests crops high, to maintain efficiency, but the front was lowered to “beer can height” to maximise ryegrass seed capture and deployment onto the tramlines.

Later this year, Roger expects to have a better idea of how well the chaff deck performed in confining weed seeds, machine losses and chaff to the tramlines, and the impact of traffic on weed seed germination.

Other tactics

Aside from HWSC, another weed management tactic Roger employs is a diverse crop rotation that allows him to use a variety of herbicide groups with different modes of action.

After he bought a 12-metre NDF disc planter set on 304.8mm (12-inch) row spacings in 2010, Roger introduced a six-year rotation comprising one year of fallow, followed by canola/wheat/chickpeas/wheat/barley.

However, this year, paddocks are being transitioned to a four-year rotation comprising one year of fallow, then canola or chickpeas/wheat/barley.

A shorter rotation not only gives the soil a rest sooner, allowing weeds to be controlled during the year-long fallow, but also enables lime (and gypsum if necessary) to be incorporated with pre-sowing tillage, Roger says.

In 2017, he tried higher sowing rates in some paddocks, to boost crop competition, but was not happy with the result because of high pressure from silvergrass. These areas will be fallowed and double-knocked in 2018.

Variable rate lime

Another change on the agenda for the business is the gradual introduction of variable-rate lime application across the farm.

Traditional composite 10-centimetre soil tests have revealed some topsoils have a pH of 5.0, so this year funds usually invested in gypsum are being reallocated to lime to lift soil pHCa to 5.5.

In the past, Roger routinely applied 700 to 900 kilograms per hectare of lime but, mid-year, samples will be taken on a grid layout to develop pH maps and better target lime rates according to the soil’s needs.

Through Chris Baker, a contractor will collect GPS-referenced in-situ soil pH (water) measurements to pinpoint where high, medium and low soil pH zones exist.

After reviewing the data, soil sampling points and soil samples will be collected to ground-truth the in-situ soil test results in pHCa and calculate precise lime rates for the defined zones.

Research wish list

As reliable full-time farm workers are difficult to find in the Condobolin district, Roger longs for the day that he can deploy an automated planter to sow his crops.

“The young people around here are not really interested in agriculture,” he says. “The only people coming back are kids from farms and there are not many of those either, because half are finding careers outside of agriculture.”