The dynamic nature of farming means that growers are always tweaking their enterprise mix, trying new crops, and perhaps adding or removing livestock. Such changes bring the usual challenges, although one unexpected aspect can be the consequences for a farm or district’s biosecurity status.
This has been highlighted in long-term surveys of Victorian farmland, and the intensifying cropping in that state. Plant Health Australia (PHA) grains biosecurity officer Jim Moran, from the Victorian Department of Environment and Primary Industries, says among the significant changes documented in the Mallee and the north-west regions of Victoria are the decline in pasture and fallow periods and reduced variety in rotations. There has also been a corresponding increase in cropping intensity.
Annual or biannual land-transect surveys, supported by state and federal funding, have been undertaken annually in the Wimmera since 1996, and since 1998 in the north-west. This year, a survey was also introduced in Victoria’s south-west, which has identified a historic shift from grazing to cropping – from about nine per cent of paddocks surveyed to more than 40 per cent.
Mr Moran says that when a traditional grazier moves into cropping some major biosecurity challenges arise. “Even the best-managed farm biosecurity system for a pasture-based enterprise is no match for the different pests and diseases and weed pressures faced by cropping enterprises,” he says.
“Suddenly questions of certified seed, cropping-equipment hygiene, crop rotations and sound chemical use emerge as necessary to manage a whole new world of potential risks. Removing the green bridge, for example, becomes crucial to prevent the loss of soil moisture and nutrients, and to eliminate hosts for pests and disease.”
Mr Moran says weeds in cropping systems are nothing new, but weeds adapted to annual cropping systems are generally different to pasture weeds. The way weeds can move from farm to farm and paddock to paddock can also create new challenges.
When cropping enterprises remove pasture or legumes from their rotations, or eliminate fallows, they can also exacerbate any underlying disease issues, he says. Creating a disease break is an important strategy in managing biosecurity risks and maintaining a resilient and productive farming system.
In particular the transect surveys have identified the potential for higher disease risk with the increase in oilseed plantings. The 2013 survey of the Glenelg Hopkins Catchment Management Authority transect, between Ararat and Caramut in Victoria’s south-west, found 53 per cent of the cropped paddocks were sown to oilseeds and legumes, with the remainder planted to cereals. This compared with 21.5 per cent sown to oilseeds and legumes in the northern Wimmera and 35.5 per cent in north-east Victoria (Table 1).
“There has been a huge expansion of canola plantings and, although it is early days for the south-western survey, it indicates that growers may be adopting a shorter, two-year rotation for oilseeds, without break crops, which would not adequately manage disease,” Mr Moran says.
Future surveys are expected to help track further land-use changes and allow biosecurity extension efforts to target risks emerging from new agronomic regimes.
PHA’s grain biosecurity officers can help provide information and assistance on biosecurity planning to manage new and existing risks. More information is available from Jim Moran on 03 5430 4479, or go to the Grains Farm Biosecurity Program webpage for the contact details of the grains biosecurity officer in your state.
Article written by Catherine Norwood and reproduced with permission from the Grains Research and Development Corporation.