Dr Gustavo Boitt1, Dr Andreas Neuhaus1, Mr Peter Rees1
1CSBP, Kwinana, Australia
Biography:
James is a Senior Agronomist at CSBP. He joined the company in 1988 after graduating from the University of Western Australia with a degree in Agricultural Science (Hons), specialising in soil and plant nutrition. James has had a long association with the Company’s extensive Field Research program and enjoys working closely with colleagues and industry consultants to improve fertiliser advice to Growers.
Abstract:
Continuous cropping without legumes in the Western Australian grain belt has depleted soil nitrogen (N) reserves. In the last 30 years, legumes have declined from 20% of the cropped area to about 4%, and increased cropping has taken the place of productive legume based pastures. In addition, increased crop yield potential from soil amelioration, improved genetics and better agronomic practices have increased the demand for N. It may take more than higher N rates to maximise returns in better seasons and there is greater financial risk from increasing N fertiliser rates. In 2021 and 2022, CSBP established a series of replicated small plot trials in the central grain belt of Western Australia to determine the potential benefits of growing legumes to following crops – including the effects on responses to N fertiliser. At Dandaragan, there were similar responses to 118 kg N/ha in wheat after lupins (W/L) as wheat after canola (W/C), but yields were 1.5 t/ha higher after lupins. At Meckering, with 118 kg N/ha applied, canola after lupins (C/L), was 1.1 t/ha higher yielding than canola after wheat (C/W). The results from Dandaragan and Meckering show that a productive legume may be required in the rotation to capitalise on the good seasons, especially if soil N reserves are low and yield potential has increased following soil amelioration. At Bruce Rock and Toodyay, higher N rates on W/W and C/W did produce the same yields as W/L and canola after faba beans (C/FB), but higher grain/seed N concentrations after the legumes indicate that these rotations could have produced higher yields with lower risk had yield potential been higher. Collectively these trials show the potential for increasing cropping returns in high yielding environments with the inclusion of legume crops in the rotation.