Research update for the long-term subsoil acidity experiment at Cootamundra, NSW

Abstract

Key findings • • Deep placement of organic amendments (e.g. lucerne pellets) did not increase soil pH as high as measured in laboratory/glasshouse experiments, but it did reduce exchangeable aluminium (Al) significantly at 10–20 cm and 20–30 cm, indicating that the organic amendment would relieve Al toxicity by combining Al3+ to form insoluble compounds, hence reducing toxicity to plant growth. • • There was a large crop yield response to deep organic amendments in year 1 due to extra nutrients supplied from the lucerne pellets, but no crop response was detected in year 2, partly due to lack of soil moisture during the crop growing season. To date, soil treatments have had little effect on soil water. • • Soil chemical, physical and biological properties will continue to be monitored to understand the soil–plant interactions, the factors driving the differences in crop response to the various treatments, and the residual value of the amendments over the long-term.