A team of researchers across WA are working to devise the best strategies to maximise crop establishment post deep tillage.

Strategic deep tillage has been gaining momentum across the sandplain areas of Western Australia as yield gains demonstrate its benefit.

To maximise the benefits of this form of amelioration DPIRD Senior Research Scientist Wayne Parker is working with a team of researchers across regions of WA to learn more about the agronomic needs post deep rippling to optimise performance of crops.

Mr Parker has been a part of a team including Dr Steven Davies, Dr George Mwenda, Andrew Blake, Tom Edwards, Ranny Wilkins, Melanie Kupsch, Amandeep Kaur, and Jack Hughes involved in a large five-year GRDC-supported project investigating farming system aspects of deep tillage. The project has spanned the Geraldton, Kwinana West, Albany and Esperance Port Zones.

“Strategic tillage is a comprehensive once-off operation used to alleviate multiple constraints,” Mr Parker says.

“It commonly is carried out with spaders, mould board ploughs or modified one-way ploughs to a depth of 400 millimetres or more.”

“The project has incorporated 14 to 18 trials per season and has covered a broad range of agronomic aspects including herbicide use and pathology studies following deep tillage.”

Crop establishment and maximising groundcover post deep ripping is vital to not only set a crop up for maximum yield but also to minimise soil exposure to wind erosion.

Mr Parker says that the timing of deep tillage is probably of the highest priority.

“Overall, we found that strategic deep tillage can compensate to some extent for later sowing.”

“If the amelioration operation can be delayed until May following rainfall when the soil is wet, it can not only reduce exposure of the soil it may also reduce wear and tear on equipment.”

“One-pass operations combining amelioration and seeding increased crop establishment by 13 to 61 per cent compared to two-pass operations, but weed control and the logistics for growers to do this are challenging.”

Soil packing after the deep ripping operations and prior to seeding was found to consolidate the topsoil which improved trafficability. However, the use of heavier rollers did not improve crop establishment or grain yield. Rolling ridges was found to provide only minor protection from wind events.

Crop variety choice after amelioration is important and can be regionally and season specific. The use of high-quality seed is a requisite together with an appropriate season fit.

“Longer-season varieties can capitalise on early-season amelioration operations that arise from early breaks in the season in April.”

For time of sowing trials amelioration treatments were carried out just prior to sowing at every site.

“In 2022 at the Ogilvie site in the Geraldton Port Zone a cool and wet finish to the season resulted in the highest yields from the May time of sowing (TOS) with amelioration increasing grain yield by 1.27 tonnes per hectare compared to 1.0t/ha for the June TOS. The longer-season Rockstar had the highest yield in both April and May TOS whilst shorter-season varieties like Vixen performed better in June TOS.”

At the North Cunderdin site in the Kwinana West Port Zone in the 2022 season the April TOS had the highest yield for the control (un-ameliorated) treatment but the May TOS ameliorated treatment was the highest yielding overall.

Due to the nature of the deep tillage operation and generation of a soft seed bed seed can end up being sown deeper than intended. In these circumstances the use of long coleoptile cereal types is a good insurance tool to improve crop establishment.

“Across two sites at Merredin and Yuna in 2023 wheat with the long coleoptile trait had 18 to 47 percent better establishment when sown deep on ameliorated soils.”

In 2022 at the Ogilvie site the result was even greater where long coleoptile types increased establishment by 232 per cent.

Increasing the seeding rate remains one of the most reliable means of improving crop establishment in both ameliorated and non-ameliorated situations.

“Seed rate increases from 120 plants per metre squared to 180 to 200 plants increased wheat establishment by 45 per cent at North Cunderdin in 2022, 65 per cent at Ogilvie in 2022 and 33 per cent at Yuna in 2023.”

“These increases in crop establishment occurred independently of wheat variety or soil amelioration. It was observed that higher crop establishment improved weed suppression. However, higher establishment did not increase final grain yield at Ogilvie or Yuna but at North Cunderdin grain yield increased between 0.3 to 0.5 t/ha.”

More information: Wayne Parker, 08 99568511, wayne.parker@dpird.wa.gov.au