While scientists grapple with technologies to reduce methane emissions from livestock, Lincoln University’s Professor Derrick Moot believes a more immediate answer to methane reduction lies in legumes.
Speaking about a changing climate at the recent New Zealand Institute of Animal and Horticulture Science conference, Professor Moot built a strong case for using legumes to drive highly efficient livestock systems – where animals are grown out and finished quickly, therefore minimising their methane emissions.
“A legume-based system can deliver on greenhouse gas targets. We’ve spent tens of millions of dollars trying to create a vaccine or breed a sheep that will reduce methane emissions when we’ve got a system that will already do this, it’s called feed the animals quick and cut their heads off, that will reduce their greenhouse gas emissions quite quickly.”
Looking at the big picture, Derrick says the fundamental driver of climate change is a burgeoning world population and the demands on this planet’s resources by close to eight billion people.
Despite all the talk, fossil fuels continue to be burnt at an ever-increasing rate, pumping carbon dioxide into the atmosphere unabated, and the main driver of this energy production and consumption is population growth.
“It’s not something that people want to talk about.”
This population needs to be fed and Derrick credits the intensification enabled by the Green Revolution, particularly the use of nitrogen (N), to the fact that no more swathes of forestry have been cleared to make way for food production.
It now takes .6 billion hectares of land to feed the world population, without intensification, 2 billion hectares would be required.
You either have intensification or deforestation, he says.
In New Zealand, N has been a critical part of agricultural intensification. Despite the exponential rise in the use of bagged N, grass-dominant pastures still remain N deficient. Carbon dioxide is also emitted in the production of N fertilisers.
Legumes are the most environmentally-friendly and cost-effective way he can think of to get N into pastoral systems and will fix N at a rate of 30kg of N/1000kgDM grown.
While the practice of “spray and pray” has come under scrutiny, Derrick, who describes over-sowing legumes onto hill country as “aerial no-till,” says this method of improving pastures has a low carbon footprint.
The N introduced through the legume helps break down thatch (which typically has a 40:1 carbon nitrogen ratio) stimulating the N cycle and providing N to chronically N-depleted pastures.
“There is minimal risk of N leaching from hill country because these pastures are so N deficient.”
Getting N in the system can increase drymatter production on hill country by 75%, so long as basic science is adhered to and molybdenum levels are adequate. Legumes require molybdenum.
Derrick says farmers need to identify which legume to grow where and while subterranean clover is ideal for north facing, dryland hill country, lucerne and red clover can be grown on easier or very intensively farmed parts of the farm.
Managed correctly, legumes can drive daily lamb growth rates of 300gms and over, which means lambs can be grown and finished very quickly post-weaning in about 33 days.
Derrick says his focus is getting N into farming systems and the most cost-efficient way to do this is to use legumes.
Capturing the nitrogen accumulated in the soil in the wake of winter grazing, and using it to grow high-quality feed in spring, is good for...