Soil acidity is an environmental and economic concern in Australian farming systems with negative impacts on soil fertility, biological activity and the productivity of crops and pastures.
In this article for World Soil Day, Graham Centre for Agricultural Innovation member, Dr Jason Condon, who works as a NSW Department of Primary Industries (DPI) soils scientist and Charles Sturt University (Charles Sturt) senior soils lecturer, reflects on the research so far and how we are training scientists for the challenges ahead.
Foundational work into acidification and acid soil management has been conducted in Wagga Wagga since the late 1970s.
Over the last 20 years Charles Sturt PhD students have been working on agronomic and soil chemistry impacts of soil acidity. Their research has identified the processes causing the formation of acid layers within the top soil of our crop and pasture systems. These layers create what is known as pH stratification.
NSW DPI has conducted several long term studies investigating possible management options for acid soils. One of these projects, a Grains Research and Development Corporation (GRDC) co-investment with the department, led by NSW DPI research scientist and Graham Centre member Dr Guangdi Li is investigating deep placement of liming materials to ameliorate subsoil acidity.
Additional research has focused on the impact on pH stratification on legume performance. NSW DPI and Charles Sturt staff are working with grower groups from the Holbrook Landcare Network, FarmLink and NSW Local Land Services in Bega, Berry, Yass and Goulburn to deliver workshops on soil acidity and conduct demonstration and research trials investigating acid soil management with funding from the National Landcare Program.
The Graham Centre is supporting a suite of Honours and postgraduate students to continue to research issues of pH stratification.
Mr Han Nguyen is in his final year of his PhD researching the role of organic matter in improving the movement of lime deeper in the profile. Also in her final year of PhD study, Ms Brooke Kaveney is investigating the role of pH stratification and liming on effectiveness of nitrification inhibitors.
The impact of pH stratification on the breakdown of herbicide residues and their effect on legume growth and nodulation is being investigated by Charles Sturt Honours student, Ms Anne-Maree Farley (pictured left) while another Honours student Mr Tom Price (pictured below), has successfully demonstrated the effectiveness of prilled lime placed in the seeding row of pulse crops on overcoming the effects of pH stratification. The research was also able to demonstrate that for the local soil, soil sampling should be conducted in depth intervals of 5 cm rather than the standard practice of 0-10, 10-20 cm intervals in order to accurately identify the presence of pH stratification.
Soil acidity and pH stratification has been identified as a major constraint to agricultural production and overcoming this problem will form more productive soils enabling our plant based agricultural systems to be more resilient to conditions of climate change. The Graham Centre’s researchers from Charles Sturt and NSW DPI, in collaboration with grower group networks and private companies continue to support agricultural industries by leading research into soil acidity. The development of a new wave of soil researchers trained at Charles Sturt with supervision from CSU and NSW DPI scientists will ensure industry has a skilled research-based workforce to address the soil problems of tomorrow.