The effects of increased soil temperature on Phosphorus (P) availability in Tasmanian soils

The dependency of P fertilisers has increased to counteract P deficient soils and increase soil productivity, particularly in Tasmania to achieve a $10 billion annual net valued agricultural sector by 2050. However, the effects of extreme climatic conditions due to human-induced climate change on P availability has been insufficiently studied in comparison to other soil nutrients such as nitrogen. Forecasting movement of P throughout the soil based on specific conditions not only advances current knowledge but will allow appropriate P management strategies to be implemented. Currently it is known that increased soil temperature will cause P availability to decline. However, no studies have attributed this relationship to human-induced climate change nor soil mineralogy. Here we show that increasing soil temperature of a Tasmanian Ferrosol and Dermosol to 45 ℃ causes the rate of sorption to increase, resulting in over 50% of applied P to be sorbed by day 15 in both soil types. Although the Ferrosol and Dermosol displayed similar P sorption trends, the magnitude in which it occurred at has been attributed to differences in soil mineralogy. We also found that the deposition of P in the Ferrosol was comparable with other studies, while higher temperatures caused the behaviour of the Dermosol to become unpredictable. Understanding these effects allows both soils to be treated as two separate systems to enable optimal P availability to be achieved. This can allow P inputs and specific management strategies to be implemented to maintain Colwell P, reduce P losses to the environment and reduce the reliance on costly P fertiliser inputs while maintaining, if not increasing agricultural productivity.