Local Govt | National News Video | Parliament Headlines | Politics Headlines | Search


Eruption’s agricultural risk analysed

Thursday, August 9, 2012

Eruption’s agricultural risk analysed

Massey University researchers say ash from this week’s Mt Tongariro eruption poses no great human health or agricultural threat.

Massey University's Volcanic Risk Solutions and the Fertiliser and Lime Research Centre, together with University of Canterbury researchers, tested ash samples collected beside state highways 46 and 1, near the volcano, along with one sample collected from Gisborne.

Professor Shane Cronin says initial tests show moderate levels of soluble Fluorine. “Concentrations between 20 and 70mgF/kg of ash were measured, which is in a similar range to the widespread volcanic ash produced during the 1995 and 1996 eruptions of Ruapehu,” he says. “Due to the restricted distribution and very thin ash fall, this currently poses no current human health or agricultural threat beyond the immediate vicinity of the volcano. In addition, heavy rainfall since the eruption has removed much of the ash and associated contaminants.”

If future, larger eruptions of Mt Tongariro also produce ash with similar concentrations of Fluorine, a significant agricultural hazard can be anticipated. “Ashfall can impact pastoral grazing systems by covering pasture, meaning that it is ingested by grazing sheep, cattle and deer,” Professor Cronin says. “Further, livestock drinking water in open troughs may be contaminated. Additionally, rural dwellers with roof-catchment drinking water sources should be vigilant in avoiding ash runoff into water tanks. During and immediately following ashfall the intake pipe to water tanks should be disconnected until ash has washed off the roof with rain.”

In grazed pastoral systems, following ash cover, some livestock will be put off grazing by the high levels of acidic and abrasive ash, while others will continue to graze. If supplementary feed is unavailable, this may lead to starvation of stock, especially pregnant or lambing/calving stock that face high energy demands at this time of year.

Professor Cronin says if significant ash is ingested along with pasture, livestock are also at risk of the disease Fluorosis. “Experience from the 1995-96 eruptions has shown that ash coverings greater than two millimetres, low-grazed pastures, and low rainfall following ash deposition are critical factors increasing hazard.”

Deaths of stock normally begin 4-10 days after ashfall if no supplementary feed is available. Heavy or persistent rainfall quickly disperses levels of ash and also rapidly leaches the fluorine, reducing the hazard considerably.

Professor Cronin says deer are likely to be the most susceptible to Fluorosis, followed by cattle, with sheep being the most resistant. Fluoride is absorbed rapidly by grazing animals from ingested ash or contaminated water – but in moderate levels it does not pass into milk.

In the event of future ashfalls he has the following advice for farmers:
1. If ash fall exceeds 2mm or coats more than 50 per cent of pasture/feed crops, either move stock to less affected areas of the farm or supply supplementary feed.
2. In these situations also refill stock drinking troughs from bore or river supplies.
3. If ash has not washed off pastures after 2-3 days, raise the quantity of supplementary feed and monitor stock condition closely.
4. In general, to reduce impacts from ashfall, maintain pasture length by regular rotation rather than close cropping. Longer pastures are less likely to be completely covered.

For rural residents with roof-fed tank water supplies:
1. Temporarily remove downpipe connections to water tanks during and following ashfalls to protect stored water.
2. If possible, wait until rainfall clears ash from roofs before reconnecting intake.
3. Water affected by ash will appear turbid (cloudy) and may have a bitter taste. If this is the case, avoid drinking this water and seek alternative supplies.

© Scoop Media

Parliament Headlines | Politics Headlines | Regional Headlines

Gordon Campbell: On The Leaders Debate

Do political debates change voter intentions, and cause voters to switch sides? According to a 2019 Harvard Business School study conducted across 61 elections in nine countries involving 172,000 respondents, the answer would seem to be a resounding “No.” Political debates have little effect on voter behaviour, let alone on election outcomes. Crucially, the limited effect they do have does not involve a change in voters’ policy preferences... More>>


National Agriculture Policy: Will Restore Farmer Confidence And Pride

A National Government will reduce regulatory burden and give farmers confidence for the future. Leader of the National Party Judith Collins and Agriculture spokesperson David Bennett announced National’s Agriculture policy in Gisborne today. “Agriculture ... More>>


Shaw: Wealth Tax Not A Bottom Line For Green Party But They Will Push For It

Green Party co-leader James Shaw says one of his senior MPs misspoke under pressure when she said a wealth tax was one of the party's bottom lines. More>>


Government: More Border Exceptions For Critical Roles

The Government has established class exceptions for border entry for a limited number of veterinarians, deep sea fishing crew, as well as agricultural and horticultural machinery operators. “Tight border restrictions remain the backbone of the Government’s ... More>>


PM: Auckland At Bolstered Level 2, Rest Of Country Provisionally At Level 1

Pandemic alert levels for the whole country have been reviewed by Cabinet and Prime Minister Jacinda Ardern is announcing whether restrictions will be eased. More>>


Dunne Speaks: The Election Campaign Just Grinds Slowly On And On

With just over three weeks until the General Election, the release of the first major pre-election opinion poll this week confirmed what was already being reported about this year’s campaign. Although the gap between Labour and National has narrowed ... More>>

Electoral Commission: Candidate And Party Lists Released

17 registered political parties and 677 candidates will be contesting the 2020 General Election Nominations have now closed and the Electoral Commission has released the electorate and party list candidates for 2020 online at vote.nz . Advance voting ... More>>

National: Plan To Restore NZ’s Prosperity

National’s Economic and Fiscal Plan carefully balances the need to invest in infrastructure and core public services while also reducing tax pressure on Kiwi families and businesses. National Leader Judith Collins and Finance spokesperson Paul Goldsmith unveiled National’s ... More>>


NZ First: Party List

New Zealand First has a proven twenty-seven-year history of bringing balance and common sense to our government. Amid the continued setbacks of COVID-19 restrictions, New Zealand First has once again sustained its profile by selecting a strong team ... More>>

Election: Arriving Travellers In Isolation To Be Able To Vote By Telephone

Up to 5,000 people in managed isolation or quarantine will be able to vote by telephone in the general election and referendums after an amendment to electoral regulations last week. Chief Electoral Officer Alicia Wright says the Electoral Commission sought ... More>>





InfoPages News Channels