Biological Capacity and Resilience As a Measure of Soil Biological Health.

Maintaining soil biological health, an integral part of overall soil health, is critical for the improvement and sustainability of agricultural industry and its interaction with the overall health of terrestrial and aquatic ecosystems regionally. Existing soil health indicator tests generally include a single measure for soil biology such as microbial biomass or microbial activity. However, experience from both cropping and natural systems has shown that such single property tests are inadequate to indicate the status of a diverse soil biota and their functional capacity in terms of C sequestration, nutrient availability or loss and disease suppression. Recent knowledge from research in agricultural systems worldwide has indicated that a functional approach to soil biological diversity and processes provides a useful measure of soil health in terms of plant nutrition and health, nutrient use efficiency, C sequestration and overall ecosystem health. Therefore, for an effective soil biological health test, it is the functional response of soil biota to changing management that should be measured and quantified in order to develop cropping systems that improve the functional capacity and resilience of soil biota. A ‘three-component testing system’ involving measures of (i) catabolic diversity (carbon turnover), (ii) genetic potential (abundance of functional genes) and (iii) functional capacity (biochemical tests) can provide a reliable and integrated measure of the capacity of soil biology. Such an integrated measure would also be suitable to quantify the resilience of soil biological capacity giving an integrated picture of overall soil biological capacity to withstand disturbance and chemical use. These measures would also complement pathogen-based assessments to determine the potential for disease risk and impacts on productivity. This type of function-based information would fit with developing regionally specific benchmarks and interpretation guides for soil biological health measures as part of an overall soil health test-set including physical and chemical tests.