The benefits of perennials in filling feed gaps, improving water use and protecting fragile soils is well recognised, but incorporating them into the cropping system still presents many challenges
With more than 50,000 hectares of perennial grasses sown in the northern wheatbelt and about 150,000ha of kikuyu pasture in the south, there is significant potential for pasture cropping in Western Australia. The practice, which involves sowing a winter-active crop over a summer-active perennial grass or legume, can provide an alternative feed source or even a cash crop.
When growers in WA’s northern wheatbelt over-sowed with winter cereals to produce additional feed when perennial growth slowed in winter, they found the performance of the winter cereals was often greater than initially expected, prompting some growers to retain the cereal crops through to grain harvest. Growers in the south are also experimenting with pasture cropping, prompting EverCrop researchers to study the benefits.
In a trial at Moora from 2009 to 2012, researchers from the Department of Agriculture and Food, WA (DAFWA), found that when barley was sown over different perennial species (Rhodes grass, Gatton panic and siratro) and in line with district practice (50 kilograms of nitrogen per hectare), pasture cropping did not significantly reduce crop yield. However, under higher-input conditions (80kg N/ha), the perennial pasture base reduced cereal crop yields by up to 26 per cent.
Not only did pasture cropping prove to be profitable at Moora, but the perennial pasture and pasture-cropped treatments also reduced deep drainage by about 50 millimetres per year compared to the annual crop-only treatment. Despite differences in root depth between the perennial (3.5 metres) and annual crop (1.5m) systems there were no significant differences in soil carbon to a depth of 4m. However, microbial activity and biomass were higher with perennial-based systems.
Between 2012 and 2014, the EverCrop team also collaborated with growers to confirm the fit for pasture cropping over subtropical perennial grasses in the medium-rainfall zone of the northern agricultural area and along the south coast on deep sandy soil with limited capacity to store moisture from summer rainfall.
The team is now expanding investigations into the potential for pasture cropping over kikuyu pastures in the south to break up the thatch and rejuvenate legume production in the paddock following a crop. Other advantages include out-of-season feed in response to summer rain, protection from wind erosion and reduced waterlogging and nutrient leaching.
The concept of perennial grains – planting a crop in one year and harvesting grain from the same crop for several successive years – is also undergoing trials in Australia. Previous research by the NSW Department of Primary Industries at Cowra found a perennial wheat continued to yield for up to four successive years.
Initially, perennial grains are likely to be a novel grain and graze option for mixed-farming operations in higher-rainfall regions, promising to increase grain production potential in the present permanent pasture zone of southern Australia. Possible benefits of a perennial cropping system include increased flexibility to cope with variable seasonal conditions, reduced need for sowing and improved resource use efficiency compared to annual cropping systems.
Further development is still required to improve the longevity of the existing material for the Australian environment and to refine the perennial cropping system. Ongoing research is examining the potential to grow perennial grains in mixtures with a legume.
Perennial wheat lines grown with lucerne at the Cowra Agricultural Research and Advisory Station.
PHOTO: Richard Hayes
One of the common challenges facing mixed growers is managing increasingly large paddocks that are highly efficient for cropping machinery, but make feed utilisation and high grazing efficiency difficult to achieve. This is particularly the case where there are highly variable soils and areas of potentially erodible soils or poor establishment within paddocks.
Use of temporary electric fencing is not an attractive option, so it is no surprise there has been major grower interest in the potential to use virtual fencing technology for spatial grazing management.
A commercial version for cattle, eShepherd, is close to commercial release and enables growers to set GPS-based electric lines, or ‘virtual fences’, so when the animal approaches that line it learns to respond to an audio cue to deter it from going further.
Virtual fencing could allow growers to deter animals from areas where more ground cover is needed and encourage them into areas more able to support grazing or to assist with weed control.
A Mallee Sustainable Farming study that tracked sheep movements showed that sheep spent 50 per cent of the time grazing only 25 per cent of the paddock and up to a quarter of the paddock was not grazed at all, resulting in inefficiency losses valued at $4000 in one paddock alone.
When investigating the case for developing virtual fencing for sheep, EverCrop farm economic studies showed that if spatial grazing could be applied with sheep on a typical Mallee mixed farm, it could boost whole-farm profit by 15 per cent and greatly increase the role of livestock in mixed farming.
On-farm trials conducted by CSIRO in the NSW Mallee this year showed that sheep learn to respond quickly to the cues and were successfully deterred from grazing on erosion-prone areas, but substantial development is still required to commercially adapt the technology for sheep.
Virtual fencing can keep sheep away from potentially erodible soil types within a paddock.
PHOTO: Rick Llewellyn
GRDC Research Code CSA00044
David Ferris (pasture cropping),
08 9690 2117,
Richard Hayes (perennial grains),
0448 231 704,
Rick Llewellyn (spatial grazing),
0429 690 861,