An international soil scientist has spelled out the way New Zealand can meet part of its commitment to reducing carbon dioxide in the atmosphere.
Dr John Baker says it can be achieved without radical changes to farming practices. "It just requires a refinement of what's being done now," he said.
The New Zealand government, at the Paris Climate Change conference, has agreed to reduce the discharge of greenhouse gases.
Dr Baker, CEO of Cross Slot No-Tillage Systems, said New Zealand had more potential to remove millions of tonnes of carbon dioxide from the atmosphere than most other countries in the world because we had a high land-to-emissions ratio.
"It involves our farm crops and pastures utilising sunshine, which we have in abundance, to take carbon dioxide out of the atmosphere by photosynthesis and retain it in the ground undisturbed," he said.
"In doing so, New Zealand's 1 million hectares of newly established crops and pastures each year hold the key to reversing a significant portion of its greenhouse gas emissions by converting it into soil carbon which, in turn, increases crop and pasture yields."
Dr Baker said it could be achieved by New Zealand farmers learning how to manipulate the soil to their advantage.
"The remedy is to absolutely minimise any form of soil disturbance and stop burning crop residues, both of which release massive quantities of carbon into the atmosphere," he says.
Dr Baker said there was a far better method of seeding that not only retained carbon dioxide in the soil but added new carbon each time a new crop was grown.
"I'm talking about a unique form of 'no-tillage', distinctive from any others, known as low disturbance, no-tillage which has already shown spectacular results in New Zealand and around the world."
Dr Baker said the challenge was to stop our farmers' love affair with disturbing the soil. All disturbance oxidised organic matter into carbon which was the most common greenhouse gas.
Ploughing and many simple forms of no-tillage couldn't work through residue - the decaying matter left on top of the ground after a crop is harvested, he said.
So instead, farmers burned it which was the worst thing they could do. They released the carbon, which otherwise fed the earthworms and microbes and enriched the soil's health and its water holding capacity he said.
"New Zealand gets enough water and sunshine but these two commodities don't always arrive at the best times of the year. You can't store sunshine but you can store water. So it's essential New Zealand farmers learn to store more water in their soils for when it's needed," he says.
"Low disturbance no-tillage does this by recapturing carbon from the atmosphere through photosynthesis and retaining it in the soil. It's a win-win."
Dr Baker said conventional tillage, or cultivation, had stripped the organic matter from the soil over hundreds of years.
"Organic matter is the silver bullet. If you retain crop residues and leave the soil undisturbed, you increase soil organic levels and retain the soil's water storage capacity," Dr Baker says.
"To do this you need a special combo-disc-and-tine type 'no-tillage' opener that penetrates through the crop residue or vegetation on top of the soil and creates humidity-retaining seed slots beneath it without leaving the seeds embedded in the residue itself."
Such low disturbance, no-tillage drills sow the seed and fertiliser in separate bands at the same time through any amount of surface residues. Done properly the process traps the humidity, preserves the earthworms and micro-organisms, increases yields and largely prevents carbon from escaping into the atmosphere.
"Because plants absorb carbon from the atmosphere through photosynthesis this is one way of ensuring that more carbon goes into the soil than out. The method, based on university research, addresses climate change and increases the amount of food that the world produces at the same time," Dr Baker said.
Dr Baker said that if New Zealand universally adopted 'low disturbance, no-tillage', it would reduce 11 per cent of the greenhouse gases New Zealand emits and at least a quarter of agriculture's emissions alone.
"That's an incredible saving potential that is greater than almost any other country on earth except Australia," he said.