Drought is one of these natural weather phenomena set to accelerate that causes massive losses to agricultural crops, increase land degradation, reduce clean water supplies and thereby inducing malnutrition and starvation, and jeopardise global food security. One potential mitigation is the development of drought resilience in typical cropping soils by using a form of Negative Emissions Technology (NET) called Enhanced Weathering (EW), which is the application of silicate rockdust to soil and/or water. This paper will investigate the ability of rockdust to increase the water holding capacity of two typical Queensland cropping soils and also examine the silicon release from each type of rockdust, as silicon is an important plant element in drought resistance. This paper investigates the potential of Enhanced Weathering (EW), a form of Negative Emissions Technology (NET) to increase the soil moisture holding capacity of two types of Australian cropping soil by application of specific silicate rocks (geomaterials) in rockdust form. The geomaterials of focus are vesicular basalt, bentonite clay, pumice and zeolite.

The aim of this study is twofold, firstly to investigate the potential for specific types of naturally-occurring rocks and minerals (vesicular basalt, pumice, bentonite, zeolite) to improve soil moisture-holding capacity of common Australian cropping soils. Secondly, to analyse the nutrient release of the geomaterial in leached soil with particular focus on silicon.Climate change means that future projections of extreme weather events are set to escalate in frequency and intensity. Four types of geomaterials will be used for rockdust: vesicular basalt; bentonite clay; pumice and zeolite. Using six application rates control (0t/ha), 5 t/ha, 10 t/ha, 20 t/ha, 40 t/ha and 100 t/ha and overnight oven temperatures of 30°C, 35°C, 40°C, 45°C, 50°C, 55°C and 60°C, each treatment started at field capacity. Total water loss was calculated inclusive of soil moisture, geomaterial moisture and water added for field capacity. Initially, there were no clear results indicating that the geomaterials reduced water loss. The bentonite treatments developed cracking at higher temperatures and condensation was evident on the inside of the all of the containers. It was noted that the weights of each treatment were continually decreasing on the scales hinting that water loss had not reached its equilibrium. Further experimentation revealed that the treatments required 6-8 days in the oven to reach this equilibrium, which would be more reflective of drought conditions. However, a final experiment that focused on the sandier soil with bentonite applied at higher rates did conclude with a definite reduction of water loss at 40°C. Nutrient testing on the soils showed that zeolite released the highest amounts of silicon in leached Quilpie soil, however, silicon was not released in the soil water of the Mungindi soil.