Wednesday, 04 September 2019 12:55

Setting Olsen P targets

Written by  Dr Bert Quin, managing director of Quin Environmentals (NZ) Ltd
New Zealand soils are mildly acidic. New Zealand soils are mildly acidic.

A new scientific article on the management of soil phosphorus makes fascinating reading, writes Dr Bert Quin, managing director of Quin Environmentals.

The article is entitled ‘A Global Perspective on Integrated Strategies to Manage Soil Phosphorus Status for Eutrophication Control Without Limiting Land Productivity’, published in Journal of Environmental Quality, July 2019.

It was co-written by 15 scientists from several countries, including Lucy Burkitt from Massey University, and Murray Hart, formerly a senior research scientist for Summit-Quinphos before moving to Australia.

Here are a few direct quotes from the article:

‘Phosphorus losses from agricultural soils are hard to mitigate because they occur in both dissolved and particulate form, and are transported from highly variable source area…. Managing soils and soil P status represents an important strategy for the mitigation of eutrophication’.

‘Modern agriculture has come to rely on maximising the availability of P in soils through [so-called] insurance application rates of highly soluble P fertilisers to build up soil P fertility and minimise risks to productivity. This makes it harder to manage resulting soil P losses’.

‘Legislation to help reduce (loss-inducing) threshold soil P test values has been generally slow to implement despite widespread eutrophication problems’.

‘Our analysis spanned three continents and catchments with different ago-hydrochemical functioning. The study areas were expected to represent variable run-off response, soil P response patterns and erosion vulnerability’.

‘All data sets showed a highly significant effect of soil P status on P runoff concentrations’.

‘Future sustainable P management within the food system must reconsider old philosophies that place undue emphasis on maintaining an artificially high level of P fertility dependent on inputs of highly soluble manufactured fertilisers towards new philosophies that concentrate on precision feeding of the crop not the soil’.

‘Our meta-analysis across three continents suggests agronomic optimum P concentrations need to be in the range of 10-20 Olsen P to match challenging eutrophication control targets being set for freshwaters (around the world)’.

In New Zealand, where all our soils are mildly acidic, we have the enormous advantage that we could maintain high pasture production levels without Olsen P levels needing to be pushed above 20, simply by avoiding the use of soluble P fertilisers such as superphosphate where sustained-release P fertilisers like reactive phosphate rock (RPR) will maintain at least as high production, with much less P run-off and leaching. 

Dairy farmers, you need to figure this reality out for yourselves soon, before you are forced to destock. Unfortunately, vested interests in a small country like ours prevent the fair and open discussion of scientific knowledge.

• Dr Bert Quin is managing director of Quin Environmentals (NZ) Ltd.

More like this

Council tasked with making unworkable work

Following a meeting between farmer representatives and environment and ag ministers, Environment Southland will be setting up a local advisory group for freshwater rules.

Farmers try to rectify mistakes

After hearing about problems with the Government’s new freshwater regulations, Tony Cleland organised a meeting between farmer representatives and the Ministers for the Environment and Agriculture.

Well meaning rules do not mean well

OPINION: Investing in environmental improvement makes a lot more sense than paying for bureaucratic processes that are perceived to add no value.

Featured

 

New Feds man keen to build

New Feds board member, William Beetham wants the organisation recognised for its significant contributions to NZ farming and society as a whole.

National

Global movers and shakers

Dairy companies around the world are facing a dilemma – whether to expand or divest assets, says Rabobank’s Mary Ledman.

Live cattle exports in limbo

The fate of 28,000 cows in quarantine in New Zealand and supposedly destined for China in the coming weeks hangs…

Machinery & Products

Mowers get a makeover

Well known throughout New Zealand over the past 18 years, Pottinger has redesigned its rear-mounted Novadisc mowers to incorporate a…

Hardy spotlight

High quality, reliable lighting is essential for anyone involved in agriculture or the great outdoors.

Simmm twin water blasters

Italian made Simmm Power Cleaner 100/11 and Power Gun 100/11 single-phase (230 volt) electric water blasters are proving popular in…

OPD argument raging on

A stoush is brewing with the Federal Chamber of Automotive Industries (FCAI) heavily criticising Farmsafe Australia’s recent Safer Farm Report.

» Latest Print Issues Online

Milking It

Cows and earthquakes

OPINION: It has long been suggested that animals have senses that humans don’t, and often behave differently than usual shortly…

Battle is on

OPINION: One of Australia’s biggest dairy businesses is back on the market after the Federal Government knocked back a bid…

» Connect with Dairy News

» eNewsletter

Subscribe to our weekly newsletter