Abstract
Background and aims Repeated surface application of lime for managing subsoil acidity is slow and ineffective, resulting in an accumulation of undissolved lime (carbonate) in the topsoil. We investigated the impact of the incorporation of undissolved lime into the subsoil to improve acidity and crop performance. Methods The undissolved lime in 2-cm layers of topsoil (0–10 cm) from three long-term experiments in Western Australia was measured. Both limed and unlimed topsoil with the acidic subsoil of the same profile was incubated at eight incorporation rates for six weeks, followed by growing barley and wheat in the incubated soil for two weeks to assess the impact on soil acidity and crop root architecture, respectively. Furthermore, a three-year-long field experiment was conducted following strategic tillage in limed and control plots to assess the impact on soil acidity and performance of wheat, canola and barley. Results A significant amount of undissolved lime was concentrated in the topsoil, amounting to 1.7, 1.8 and 1.3 t/ha for the limed plots at Wongan Hills, Northam and Merredin, respectively. Incubation of 5–25% topsoil after incorporation with the acidic subsoil was enough to ameliorate subsoil acidity and to improve root length density by up to 13-fold depending on undissolved lime content in topsoils and soil type. In the field experiment, the incorporation of undissolved lime also significantly improved subsoil acidity and canola performance. Conclusion We concluded that the incorporation of topsoil containing sufficient undissolved lime with acidic subsoil may offer a quick amelioration of subsoil acidity.