David Waters

Mechanisms of nutrient retention in biochar-amended soils of south-east NSW

Biochar has been associated with the increased productivity of highly weathered and acidic tropical Oxisols in the Amazon Basin. These Terra Preta soils have retained their fertility for more than hundreds of years and have enhanced characteristics such as soil carbon, structure, microbial activity, pH amelioration and nutrient availability resulting in improved plant growth.

While the increased retention of nutrients in biochar amended soils has previously been recorded, there has been little research on the mechanisms behind this. Biochar surface reactivity has been shown to vary with time and with abiotic processes such as temperature impacting on its capacity for nutrient retention.

David’s project is investigating the surface charge density of biochar, and its interaction with soil nutrients and soil micro-organisms in a broadacre dryland cropping context. Changes to char particle surface activity will be measured over time and under varying temperatures. The field trial will investigate the interaction of six rates of both green waste and cow manure biochars with nitrogen applied to soils sown to wheat and canola. An understanding of the mechanisms of nutrient retention within biochar amended soils is pivotal to provide beneficial outcomes in terms of agronomic production, environmental quality and system sustainability.

David’s research falls into the CRC’s Program 2 research area.

Objectives:

• Determine the mechanisms of nutrient retention in char-amended soils and the variation of retention with changes in char – abiotic and biotic influences
• Measure the impact of biochar in cropping soils of south eastern Australia.

For more information, email David.