Rhizosphere biology and crop productivity - a review

There is great potential to use the wide genotypic and agronomically induced diversity of root systems and their exuded chemicals to influence rhizosphere biology to benefit crop production. Progress in the areas of pathogens and symbionts in this regard is clear. Further progress, especially related to interactions with nonpathogenic organisms, will rely on an appreciation of the properties of rhizospheres in the field: the spatial and temporal boundaries of these rhizospheres, and the effects of structural, chemical, and physical soil heterogeneity in which the roots and associated microorganisms exist and function. We consider the rhizosphere environment within Australian cropping systems in relation to the likely success of biological interventions, and provide 3 case studies that highlight the need to characterise the rhizosphere and the microbial interactions therein to capture agronomic benefits. New techniques are available that allow direct visualisation and quantification of rhizosphere processes in field conditions. These will no doubt help develop better genetic and agronomic approaches. Future success, as with those in the past, will rely on integrating interventions related to rhizosphere biology with other management constraints of specific farming systems.