Lupins feed crop but a pest as well
Merino farmers are looking at ways to grow russell lupins as a feed crop without spreading them around the high country.
The fast growing lupin has been identified as showing potential as a feed source by researchers commissioned by the New Zealand Merino Company (NZM) because it can handle tough environments with soils containing low pH and high aluminium levels.
However, its ability to colonise on scree slopes and braided rivers can also make it a problem and Environment Canterbury has labelled the plant a serious weed. The regional council is working with the merino company to find ways to manage the lupins as a fodder crop without them spreading.
Environment Canterbury programme manager Don Chittock said the challenge was to allow production of alternative fodder crops while avoiding a high public cost of controlling their spread.
Farmers needed to know the lupins were a serious weed, he said.
"We recognise that farmers, agencies and the merino industry are looking for options to combat the dry climate and meet the Government's goal of growing production and doubling the value of primary industry exports by 2025."
Lincoln University trials showed the lupins bound soils which might otherwise blow away and tolerated aluminium levels toxic to lucerne. The trials were part funded by the Ministry for Primary Industries' Primary Growth Partnership and are part of the merino company project to improve merino genetics, health and forage.
Chittock said public funds were already being spent controlling the lupins in areas with high biodiversity values, but there were no restrictions on planting or requirements to control spread because of their pest status in the Canterbury Regional Pest Management Plan.
Braided rivers were one of the most susceptible habitats and the lupins out-competed native plants and choked nesting habitats for endangered birds.
The lupins had been discovered in inter-montane basins and foothills, montane scree slopes, alpine valley floors and wetlands and around spring-fed streams in the Canterbury high country. Their seed could be spread long distances by water, stock and vehicles.
NZM production science manager Mark Ferguson said the company planned to release a management protocol for the plant this winter and would work with other environmental groups.
"Farmers who choose to plant this fodder crop are expected to avoid spread into threatened or fragile environments."
He said research suggested the lupin spread was only likely near waterways and farmers could realise the potential of the plant with minimal risk to the environment under careful management.
"We don't want to be seen to be environmental vandals. If it turns out that these plants will spread everywhere and threaten native habitat, that's not an outcome we want."
NZM was advising farmers to keep crops more than 100 metres from rivers, streams and races to avoid seeds washing downstream and germinating along riverbeds.
The Department of Conservation says the lupins had spread into several riverbeds in the Mackenzie Country and posed a risk to native ecosystems. The Mackenzie Country's rare dryland ecosystems support more than 60 rare and threatened plant and animal species.
Government organisations had spent hundreds of thousands of dollars over more than 30 years controlling the lupins in the Rangitata headwaters. Their hard seed exterior becomes chipped when tumbled down a rocky river, aiding germination.
They were first planted along roadsides in the Mackenzie Country in the 1940s by Connie Scott of Godley Peaks Station. Her son, retired AgResearch scientist David Scott of Tekapo, has long promoted the legume's potential as a fodder crop for sheep.