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


Rain a blessing – but watch for nitrate poisoning risks

8 April 2014

Rain a blessing – but watch for nitrate poisoning risks

Rain is high on farmers’ wish list as the run of dry weather in many regions is affecting pasture growth. But nature’s blessing can come with a sting in the tail with the risk of nitrate poisoning in stock increasing when a dry spell is followed by rain or a run of moist, overcast days.

“During a severe drought, lack of moisture stops plant roots from absorbing nitrate. When the rain finally arrives, roots suck up nitrate rapidly, with the pasture accumulating high levels in the stem and leaves,” says Ballance Science Manager Aaron Stafford.

“After a drought-ending rain, it could be two weeks before nitrate levels in pasture stabilise at safe levels, provided environmental conditions are favourable. Hail or light frost can also damage plants, affecting photosynthesis and leading to elevated nitrate levels.

Aaron says plants usually absorb soil nitrogen as nitrate and convert most of it into ammonium and amino acids. But weather conditions in late autumn and winter can sometimes interrupt the conversion process, increasing the risk of nitrate poisoning.

All ruminants can be affected. Cattle are the most susceptible, sheep the least and young stock is more vulnerable than old. Nitrate poisoning sets in rapidly after an animal eats pasture or feed with excessive nitrate levels (0.21% or 2,100 parts per million and above is considered ‘at risk’).

Aaron says rape is known for high nitrate levels, closely followed by other brassicas. Vigorous ryegrass (especially annuals) can create problems, as can cereal green-feeds. Nitrate concentrations are generally higher in new plant growth and decrease with age. Stalks are highest in nitrate content, followed by leaves and then grain. Notably, young pastures (e.g. those re-sown in the last 1-2 years) generally present greater risk to grazing livestock than older pastures.

“Nitrate poisoning progresses quickly and has no ready cure so prevention is important. Testing pasture and feed for nitrate is one option but there are other ways to mitigate the risk.”

Farmers who suspect they have a high nitrate risk can use the following strategies:
• Split nitrogen applications late in the season to distribute nitrogen better. Apply nitrogen after grazing.
• Don’t put hungry stock on high-nitrate feeds. Give them a low-nitrate feed first, preferably one that takes a while to digest (such as straw or hay) so they are less likely to gorge themselves on risky pastures.
• Dilute high-nitrate feeds with low-nitrate feeds. This helps microbes in the rumen adapt to high nitrate feeds. Adjustment can take three to four weeks.
• Pasture nitrate levels are highest overnight and in the morning. Where possible constrain stock access to pasture (particularly in the morning grazing) until animals have been supplemented with low nitrate feed. This could involve in-shed feeding, use of feed pads or laneways, or fencing off areas on pasture to feed out supplementary feed and reduce pasture access.
• Minimise stock intake of pasture in the first 1-2 weeks following drought-breaking rain. This requires adequate supplementary feed to cover this most at-risk period.
• Stock lightly, so animals can selectively graze and avoid hard grazing - the lower part of stems have the highest nitrate content.
• Provide a lot of clean drinking water for stock on high nitrate forage.


© Scoop Media

Parliament Headlines | Politics Headlines | Regional Headlines



Key In NY: Prime Minister Addresses United Nations

Prime Minister John Key has addressed the United Nations General Assembly in New York, focusing on a call for action in Syria and on other conflicts, reform of the veto process and on the UN’s Sustainable Development Goals. More>>.


Gordon Campbell: On The Lack Of Accountability Over Philip Smith

In New Zealand, accountability is an exotic creature rarely glimpsed at ministerial level, or among senior management. The flight to Rio by the paedophile /murderer Philip John Smith/Traynor is no exception. More>>


More On Corrections

Gordon Campbell: On Putin’s Diplomatic Coup Over Syria

There’s a simple historical precedent for what is occurring in Syria. During WWII, the Allies joined forces with a known butcher and tyrant – Joseph Stalin of the Soviet Union – in order to defeat a greater evil, Nazi Germany… More>>


Key 'Didn't Know': Brownlee Seeks Pandas In China

While Defence Minister Gerry Brownlee is in China pushing a taxpayer funded deal to bring two pandas to New Zealand, the country’s military look set to be hit with a pay freeze, Opposition Leader Andrew Little says. More>>


Scoop Business: GCSB Willing To Extend Cyber-Attack Programme To Local ISPs

The Government Communications Security Bureau’s ‘Cortex’ cyber-security programme has been successful in helping identify and mitigate a series of cyber attacks since its introduction and an extension to cover local internet service providers is still on the cards... More>>


Gordon Campbell: On The Chris Brown Furore

Thank goodness Dame Tariana Turia has been able to inject a bit of common sense into the Chris Brown visa issue – her argument being that forgiveness has a place in this decision, and there is an opportunity here that should be taken... More>>


Get More From Scoop



Search Scoop  
Powered by Vodafone
NZ independent news