Richard C. Hayes1, Matthew T. Newell2, Philip J. Larkin3, Lindsay W. Bell4, Rick S. Llewellyn5
1 NSW Department of Primary Industries, Wagga Wagga Agricultural Institute, Pine Gully Rd, Wagga Wagga, NSW 2650, Email email@example.com
2 NSW Department of Primary Industries, Cowra Agricultural Research and Advisory Station, Binni Creek Rd, Cowra, NSW, 2794
3 CSIRO Agriculture and Food, GPO Box 1700, Canberra, ACT, 2601
4 CSIRO Agriculture and Food, PO Box 102, Toowoomba, Qld, 4350
5 CSIRO Agriculture and Food, PMB 2, Glen Osmond, SA, 5064
Maintaining desirable species in a mixed pasture sward is an ongoing challenge for growers in south-west NSW, particularly in lucerne-based pastures. This study examined the prospect of addressing this concern through separating species in drill rows at sowing, a practice change which represents a minimal impost to the farmer. A sensitivity analysis using the ADOPT decision support tool showed that the relatively low level of investment required to try the practice meant that there was potential for relatively rapid adoption provided environmental and/or profitability benefits could be demonstrated. A financial risk analysis determined that, for the scenarios tested on a 1000 ha farm, whole-farm profitability could be increased by between $523 and $3162 for every 1% increase in pasture production. Results from field experiments at 5 locations showed that spatially separating species enhanced the persistence of subterranean clover in perennial-based swards but effects on biomass were mixed. Annual pasture production was never significantly greater where subterranean clover was planted in separate drill rows compared to where it was grown in mixed rows with lucerne or phalaris, but in year 1 at three sites, biomass decreased by as much as 130% due to the separation of subterranean clover in drill rows. The study also unexpectedly demonstrated an enduring legacy of the original sowing row, with soil microbial populations shown to be twice as abundant under the sowing row compared to between rows in the third year following sowing.