G.P. McDonald1, S.L. Davies2
1 Department of Primary Industries and Regional Development, 444 Albany Highway, Albany, WA, 6330, www.dpird.wa.gov.au, email@example.com
2 Department of Primary Industries and Regional Development, 20 Gregory St, Geraldton, WA, 6530
Two small plot research experiments were established in 2016 at Darkan and Kojonup to investigate the longevity of banded soil wetting agents in duplex sandy gravel and loamy gravel soils in South-West Western Australia. Two commercial wetting agents were banded at sowing either in-furrow near the seed or banded on the furrow surface behind the press wheels. The experiments were designed to test residual or additive effects of the soil wetters by either applying or excluding them in different years to achieve different cumulative rates over the length of the trial. The 2017 crop rows were sown on or near the previous seasons rows for both trials but for the 2018 season off-row (inter-row) sowing was used at Kojonup. In the 2017 season at Kojonup some residual effect from the previous season was observed with the on-row sowing. In 2018, only treatments with fresh 2018 applications had crop yields greater than the control, with no residual effect of wetters. The Darkan site showed much smaller responses to any wetting agent treatment than Kojonup over both years. Some yield improvements were observed during the 2018 season with annual applications of wetting agents, but these were not as large as at Kojonup. Results over two sites and three seasons demonstrate that: a) annual applications are most effective at improving crop performance in repellent soils; and b) in some situations the amelioration effects of wetting agents applied in one season can carry over to improve crop performance in the next season.