Tall grass could fuel a revolution

TALL ORDER: Lincoln University researchers Steve Wratten (left) and Chris Littlejohn among giant miscanthus grass growing on trial at a Kirwee dairy farm.
TALL ORDER: Lincoln University researchers Steve Wratten (left) and Chris Littlejohn among giant miscanthus grass growing on trial at a Kirwee dairy farm.

A giant grass could be the answer for replacing Canterbury's lost shelter belts.

Miscanthus grass - a sterile hybrid from Japan - grows up to 4 metres tall and is showing promise for sheltering cows and irrigated pastures.

The versatile grass has more uses for farmers as another feed source, bedding material in calf sheds and a fuel source for renewable diesel, while centre pivot irrigators can roll over it easily.

A trial of the bamboo-like perennial grass at the Kirwee farm of Mark Williams by Lincoln University PhD student Chris Littlejohn is the first known study looking at its value as a shelter-belt plant. Trial belts are 6m wide along paddock margins for the $125,000 study funded over three years by Westland Milk Products and DairyNZ, but plantings could end up being in 3m-wide strips.

Littlejohn said miscanthus would provide good shelter for dairy cows at its mature height of 4m and reduced moisture loss in soils to produce an eight to 10 per cent increase in grass growth

"Under centre pivot irrigation, yields of 30 tonnes of dry matter per hectare are achievable.

"That produces about 9000 litres of renewable diesel per hectare at a cost of around $1.10 per litre [compared with around $1.50 at a fuel station]. In Rome, a whole fleet of city buses is powered by the renewable diesel produced from miscanthus."

Littlejohn said miscanthus was a resilient plant and had recovered easily when it was crushed by a centre pivot blown over by last year's winds and trampled by repair teams.

Ecology professor Steve Wratten, who is supervising Littlejohn's studies, said miscanthus had the potential to revolutionise dairy farming on the Canterbury Plains.

"No other product seems capable of providing these three key benefits," Wratten said.

"Effective animal shelter, effective pasture shelter and a cash return in the form of renewable diesel.

"Plus it can be used as fodder, as a superior bedding material in calf sheds, and, dried, as fuel for boilers to reduce dependence on diesel, coal and electricity."

He said miscanthus was a sterile hybrid so it could not reproduce itself by seed and spread only slowly by creeping rhizomes and could be easily controlled by grazing or spraying.

"The main function was to replace the shelter belts that dairy farmers cut down because when these enormous pivots go in a circle they can't push through the trees and shrub and this [plant] provides excellent shelter for animals, pasture growth downwind and when the irrigation comes along it passes through the growth and it flicks up again."

Miscanthus is grown in the United Kingdom for cow bedding and also in Canada as a "co-fire" for coal-burning power stations.

Miscanthus reaches its maximum height in late spring and early summer when shelter from sun and wind was needed and farmers had the option of harvesting it as a bedding source, straw or as a fuel.

The plant's nutrients return to its underground rhizomes, leaving a leaf and stem base, and it grows again the following spring.

If the grass was left standing over winter, it would eventually break down and not affect the following season's growth.

Average yields of 17 to 20 tonnes of dry matter a hectare are found in Europe, but can increase to 30 tonnes under irrigation.

Weed control is only needed in the first growing year when it reaches 1m and there are no recognised pests or diseases outside of Japan. The crops have a lifespan of 15 years and, unlike other alternatives such as flax or toetoe, the upright-growing plant does not grow a thick base harbouring rodents.

Researchers are trialling other shelter alternatives to be planted in between miscanthus to attract bees and welcome insects.

Overseas finance companies are interested in bankrolling a $1 million to $2m renewable diesel processing plant in New Zealand.

Wratten said there were opportunities to build mobile units for smaller-scale processing on farms to supply directly to farm fuel tanks or sell.

Westland Milk Products environmental manager Chris Pullen said the multi-purpose potential of miscanthus attracted Westland to the research project as the main sponsor.

Dairy and agricultural companies will be invited to a field day at the trial property on May 14 to demonstrate its potential, with a full field day for farmers held next year when the trial plots are at their best.

The Press