2 Jul 2007
The NZ Sustainability Council report A Convenient Untruth is a welcome contribution to the climate change debate say forest owners. NZFOA president Peter Berg says the fact that there may be opportunities for farmers to economically reduce their emissions of greenhouse gases, particularly nitrous oxide, is good news for all New Zealanders.
“If such opportunities can be turned into reality it will obviously help offset the country’s blow-out in emissions, about half of which come from farming,” he says.
“From a forest owner’s point of view, it means the carbon credits produced by forestry will no longer be needed to shelter the agricultural sector.”
Mr Berg says the report discusses a range of technologies. One technology that is not covered is the potential for further reducing emissions using biochar.
A form of activated carbon similar to charcoal, biochar is produced -- along with a carbon-neutral fuel feedstock known as bio-oil -- during the combustion of wood in the absence of oxygen.
“Early indications are that incorporating about 10 tonnes of biochar per hectare, in a once-only application, will lock most nitrogen in the soil until it is needed for plant growth,” he says.
“There are huge implications for all land users if forestry wastes can be used to produce an industrial fuel as well as a soil conditioning product which reduces nitrate leaching into ground water and nitrous oxide emissions into the atmosphere.”
Mr Berg says there is an urgent need for research to establish whether the results of initial studies with biochar apply in NZ farming practice.
“Even without biochar A Convenient Untruth indicates that dairying and potentially other intensive livestock industries can greatly reduce their nitrogen emissions. It’s a real breath of fresh air in the climate change debate.
“If farmers are able to implement these technologies it would lead to a big improvement in the country’s carbon ledger, primary productivity and -- indirectly -- water quality.”
1. AGMARDT to study biochar
The trustees of AGMARDT have set up a small working group which aims to stimulate debate on the importance of soil to our society and its potential role in mitigating climate change.
The group will initially focus on the mechanisms and practices that would enable New Zealand to grow more soil than it uses post-2012. Storage of carbon in the soil is seen as a key contributor to achieving carbon neutrality and, among other topics, the potential of bio-char will be examined.
2. Soils approaching nitrogen overload
Soil Horizons, issue 12. See article on page 2
Research is confirming that soils have a finite ability to store nitrogen, and that because they have already been accumulating nitrogen for many years, many will become nitrogen saturated in the next 50 years or so. Research also confirms that as soils approach nitrogen saturation, with a carbon to nitrogen (C:N) ratio of about 10, more applied nitrogen is available for plants, but there is greater likelihood of increased nitrate leaching and nitrous oxide (a greenhouse gas).
We have been fortunate in New Zealand because our soils, with generally high organic matter contents, can store much of the nitrogen from fertilisers and biological fixation. The ratio of carbon to nitrogen in soil organic matter varies widely, generally being lower in intensively used land such as pasture, but being greater in forest. A soil with a high C:N ratio usually has the capacity to store more nitrogen.