MANY FARMERS have long recognised the value of a good windbreak - but what are the real gains in profitability and sustainability?
Helen Cleugh from CSIRO Land and Water took on this question as part of the National Windbreaks Program. "We investigated the long-term effects of wind shelter on yields of .wheat, maize and mungbean crops around Australia's cereal-growing region using computer models with large amounts of real data, and predicted no decline in yields anywhere," says Dr Cleugh.
"While the potential gains ranged from negligible to over 20 per cent, the biggest gains were simulated at locations with lower cropping seasonal rainfall where there is greater likelihood of water deficit at grain fill," she said.
The National Windbreaks Program was one of the most comprehensive studies of windbreaks so far undertaken anywhere in the world. It investigated how windbreaks work, how they might limit productivity, and how farmers can effectively design and maintain them.
Dr Cleugh said farmers need to account for the costs associated with establishing and maintaining a viable windbreak, and identify what other products and benetits the windbreaks might provide.
The main benetits of windbreaks to plant and animal production are:
- wind erosion control
- shelter and reduced animal losses reduced physical damage to plants, including plant knockdown (lodging)
- microclimate moderation and improved water-use efficiency
- provision of shade.
"Windbreaks aren't a magic-bullet," Dr Cleugh said. "They can only improve agricultural productivity if they change some factor that is already limiting."
Windy environment and crop yield increase
For example, research in south-western WA found that, in dry windy years, average yields of crops within "20 windbreak heights" of a windbreak were around 25 per cent greater than those of unsheltered crops that suffered damage from sandblasting ("20 windbreak heights" is the distance into the crop that is 20 times the height of the windbreak) .
The best windbreak design will depend on the benefits the graingrower is seeking. Some main aims could be to protect crops from potentially damaging winds, to boost crop growth or a range of other objectives. The windbreak itself may also present opportunities for wood production, biodiversity conservation and improving the amenity of the property, she said.
"Studies from the National Windbreaks Program have demonstrated that windbreaks on farms offer many benefits with good design and management.
"Although the gains in crop yield for most parts of Australia are likely to be small, the shelter offered from occasional extreme winds can make the difference between a reasonable crop and none at all."
The findings of this work are presented in an easy-to-read, fully illustrated book, Trees for Shelter: A Guide to Using Windbreaks on Australian Farms. It is the second publication in the Agroforestry Design Guidelines series produced by the Joint Venture Agroforestry Program (JVAP). The first in the series is Trees, Water and Salt, reviewed in the last issue of the National Dryland Salinity Program's SALT Magazine.
Obtain Trees for Shelter by phoning 02 6272 4819 for $34 inc GST + P&H.