Stephen Davies1, Tim Boyes2, Liz Petersen3, Chad Reynolds1, Joanne Walker1, Ty Fulwood4, Rob Dempster5
1 Department of Primary Industries and Regional Development, 20 Gregory Street, Geraldton, Western Australia, 6530, www.dpird.wa.gov.au, firstname.lastname@example.org,
2 agVivo, PO Box 80, Stoneville, Western Australia, 6081,
3 Department of Primary Industries and Regional Development, 3 Baron-Hay Court, South Perth, Western Australia 6151,
4 ‘Meenar’ Farm, Meckering, Western Australia, 6405,
5 ‘Adair’ Farm, Goomalling, Western Australia, 6460
Over the past 10-years numerous strategic deep tillage methods have been developed for ameliorating sandplain soil constraints in WA. Degree of soil disturbance varies: deep ripping loosens soils with low topsoil impact; ripping with inclusion generates seams of incorporated topsoil; deep mixing incorporates topsoil and amendments to 0.3-0.4m; and inversion buries topsoil (and weed seeds) in layers at 0.15-0.4m. Replicated field experiments comparing 13 strategic deep tillage combinations, were established on deep sand (0.4-0.6 m) over clayey gravel (duplex sandy gravel) and deep yellow sand in 2016 and 2017, respectively. On duplex sandy gravel, treatments with deep ripping to 0.5m+ increased wheat yields by 39-49% in 2017, but combining ripping with mixing or inversion has had more sustained yield increases of 42-62% in barley for 2018. For the deep sand, which has limited capacity to store water, grain fill was compromised on mixed or inverted soils, with deeper ripping better matched to crop water supply in both 2017 and 2018. At this site a loss of tillers between 22 August and 12 November in 2018 reflected dry, hot conditions through September with greater losses for some of the deep mixed and inverted treatments which had higher yield potential that could not be met.