Researchers back Canterbury stubble burning
The burn-off of stubble from harvested crops may be little used overseas, but researchers are convinced of its value for Canterbury arable farming.
Stubble burning demonstration plots were a talking point for managing crop rotations at the Foundation for Arable Research's (Far) Arable Research in Action field day at Chertsey on Wednesday.
Research and extension director Nick Poole said the plots were set up to show why stubble burning was important in Canterbury, especially to growers of small seed crops.
"One of the issues addressed in (our) stubble-burning review revolved around the differences between crops and cropping systems in Canterbury - where stubble burning, particularly cereal stubble burning, is a valued rotational tool - and other cereal- growing nations such as the UK and US, where the practice is no longer carried out."
He said it was misleading to compare Australia's virtual non-use of stubble burning because New Zealand wheat crops produced greater yields and resulting residue and arable farmers made more use of seed crops.
In a Far review commissioned by Environment Canterbury, strong views initially came through that it was an outdated approach not necessary in New Ze aland, since it was not practised in other cropping countries.
Many parts of Australia operate a no till and full-stubble retention system in their cropping rotation which is suited to an environment with a growing season when low rainfall often stops crop canopy growth and final grain yield. The average wheat yield for wheat in Australia is about 1.5-2.5t/ha compared to almost 9t/ha in New Zealand last year.
Australian wheat crops produce about three tonnes of chopped wheat straw and stubble whereas wheat crops can extend to 14-15t/ha in New Zealand and produce as much as 12t of chopped straw and stubble.
This makes it more difficult to incorporate it into the next crop as done in the UK which does not have New Zealand's break crops of grass, vegetable and clover seeds. They are often established after wheat, when stubble is burnt and soils minimally cultivated.
Poole also pointed to a wet 2010 year generating larger yields of 2.5-6t/ha at a trial site in Australia and farmers, struggling to drill in the next crop, in many cases reverted to burning stubble.
Poole said growers could learn a lot from overseas systems, but also had to accept New Zealand conditions and practices were sometimes different.
"We want to preserve, dare I say it, a privilege to burn stubble, but we need to protect the community we live in."
Far's plots showed how much straw was produced by cereal crops in New Zealand compared with Australia and also a range of treatments including stubble only, stubble and straw, and incorporated straw.
Removing much of the wheat residue makes establishing small seed crops - needing precise planting and prone to failure - easier and enables better control of grass weeds and pests such as slugs.
Burning helps maintain a cropping system less dependent on agrichemicals and pesticides, such as slug pellets.
Stubble burning was among 12 topics at the field day including cereal disease management, fungicide resistance, opportunities to use dairy effluent in cropping, options for grass grub control and a possible potato partnership.