Gupta, V.V.S.R.1, Kroker, S.J. 1, Hicks, M. 1, Baudin, N. 1, Davoren, C.W. 1, Ward, P.2, Ferris, D. 3 and Llewellyn, R. 1
1CSIRO Agriculture Flagship, Glen Osmond, SA 5064; Email: Gupta.Vadakattu@csiro.au
2CSIRO Private Bag No 5, Wembley WA 6913; 3DAFWA, PO Box 483, Northam WA 6401
Summer active perennial grasses can provide a rich source of carbon and environment for soil microorganisms during the non-crop summer period. Additionally, they fill the summer-autumn feed-gaps generally faced in the winter rainfall dominated regions of southern and Western Australia. We analysed rhizosphere bacterial communities (taxonomic and functional) associated with summer active perennial grasses including Panicum species Petire and Bambasti, Rhodes grass and Digitaria sp. Samples were collected from field experiments on sandy-textured soils at Karoonda, South Australia and Moora, Western Australia. Summer active perennial grasses altered the genetic and catabolic diversity of microbial communities, microbial activity and biological processes involved in C, N mineralisation and supply in both the field experiments. Greater rhizosphere bacterial diversity under perennial grasses coupled with higher carbon inputs and greater volume of rhizosphere soil resulted in significant changes in the C and N cycling processes compared with cropped soils. However, the grasses were found to host soilborne plant pathogens such as Rhizoctonia solani AG8 during the non-crop period thereby increasing pathogen inoculum levels resulting in higher disease incidence during the cropping phase. These changes in key functions, populations of beneficial and pathogenic microbes and resilience reflect the status of soil biological health with implications to plant nutrition and health, productivity and long-term soil C status.