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

Abstract

Key findings •• Lime is the most effective amendment to increase pH and reduce exchangeable aluminium (Al). •• Deep placement of organic amendments (e.g. lucerne hay pellets) had limited effect on soil pH, but reduced exchangeable Al% significantly. •• The nutrients in lucerne hay pellets, particularly nitrogen (N), increased soil mineral N significantly, but its effectiveness depends on available soil water. In dry years, there was no yield improvement, despite more soil mineral N being available at sowing. •• In dry years, crops developed more roots at 0–10 cm, presumably to capture valuable rainfall, rather than producing deeper roots to seek non-existent soil moisture. However, in a wet year (i.e. 2016), root systems were distributed more evenly in the soil profile. •• There was no crop response in grain yield in 2017 and 2018 due to lack of soil moisture. The available soil water was in deficit for much of the soil profile during most of the growing season in 2017 and 2018 for canola and cereal crops. •• Grain protein was higher under the deep lucerne hay pellet treatments, with and without lime addition, compared with other treatments, in both wet and dry years.