Subsoil Acidity

Innovative Approaches to Managing Subsoil Acidity Activity in the Southern Grain Region

Project Partners: GRDC, FarmLink, NSW Department of Primary Industries, La Trobe University, Charles Sturt University, CSIRO, Holbrook Landcare, Riverine Plains, Southern Farming Systems
Project Code: DAN 00206
Project Duration: 2015-2020
Project Location: FarmLink Region

Background

Soil acidification is a natural process which is accelerated in areas of high agricultural productivity, high rainfall and on soils with low buffering capacities (Conyers et al., 1996). In the eastern FarmLink region, where these characteristics are typical, surface liming has been used to combat soil acidification in the topsoil (0-10 cm). Due to the very slow movement of lime through the profile and consumption of alkalinity in the topsoil however, this practice has limited potential to neutralise or prevent sub-soil acidification (Tang et al., 2013).
The detrimental impacts of low pH soils include nutrient deficiencies and toxicities (particularly Aluminium toxicity, which adversely affects root growth), accelerated nutrient leaching, breakdown/loss of clay materials, a reduction in carbon sequestration and limitations to crop and pasture options within the rotation (Ryan, 2018; Page et al., 2018).
To treat soil acidity in deeper layers of the profile, investigation of ameliorants and technologies capable of economically placing products at depth is required. This project brings together four research organisations and four farming system groups within the high rainfall area (500-800 mm) of south-eastern Australia to analyse aggressive amelioration options for soil acidity at depths of 10-30 cm. The standard farmer practice of surface liming will be compared to three intensive management options; deep ripping to 30 cm, ripping plus lime at 10-30 cm and ripping plus organic ameliorant at 10-30 cm.
FarmLink’s involvement in this project consists of two large scale replicated block trials (100 x 10 m strips), each being assessed for three seasons following treatments being executed. Site 1 (Binalong) was implemented at the start of 2016, with final soil sampling occurring in February 2019. Site 2 (Boorowa) commenced in February 2019.