Mapping available water capacity as a soil production capital metric in Australia

This study aims to identify a key soil property influencing farmland prices as a soil production capital indicator for soil security. There is generally a strong relationship between farmland price and production capital, as well as with biomass production. From a soil-centric point of view, under dryland agriculture in Australia, we hypothesise that soil available water capacity (AWC) is a key soil property influencing farmland prices and consequently can act as a soil production capital indicator. Here, we relate soil AWC of Australia to median farmland prices using digital soil maps of AWC. The results revealed that AWC from 0 to 100 cm is significantly associated with farmland prices (r = 0.31, p-value<0.05), providing a linear regression to estimate the soil production capital. As long as the AWC (mm) is above 67.6, the coefficient suggests that a 1 mm increase in AWC (mm) results in an increment of 293.6 $/ha in farmland prices in Australia. Additionally, an assessment of the anthropological impact on soils was conducted through phenosoil-genosoil differentiation analysis. We concluded that despite the shared formation characteristics of each pedogenon, soils with the highest AWC were not necessarily chosen for agricultural purposes since European settlement. Furthermore, our findings indicate that phenosoils in Queensland and Tasmania have higher levels of insecurity, likely due to intensified and inappropriate farming that may result in AWC reductions. This analysis provides another perspective to quantify the capital dimension of soil security, valuing its critical role in sustainable food systems and ecosystem services.