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

Editorial: Sense at last

OPINION: For the first time in many years, a commonsense approach is emerging to balance environmental issues with the need for the nation's primary producers to be able to operate effectively.

Dark ages

OPINION: Before we all let The Green Party have at it with their 'bold' emissions reduction plan, the Hound thought it wise to run the numbers through the old Casio.

Govt limits forestry conversions

Farmers have welcomed the Government’s move designed to limit farm to forestry conversions entering the Emissions Trading Scheme (ETS).

Save soil - take a pledge this 'world soils day'

OPINION: Soil is one of the most valuable assets that a farmer has. It is our collective responsibility to make use of soils without damaging either the soil or any other part of our environment, protecting them for our own use and use by future generations.

Featured

Dr Mike Joy says sorry, escapes censure

Academic Dr Mike Joy and his employer, Victoria University of Wellington have apologised for his comments suggesting that dairy industry CEOs should be hanged for contributing towards nitrate poisoning of waterways.

People-first philosophy pays off

The team meeting at the Culverden Hotel was relaxed and open, despite being in the middle of calving when stress levels are at peak levels, especially in bitterly cold and wet conditions like today.

Farmer anger over Joy's social media post

A comment by outspoken academic Dr Mike Joy suggesting that dairy industry leaders should be hanged for nitrate contamination of drinking/groundwater has enraged farmers.

From Nelson to Dairy Research: Amy Toughey’s Journey

Driven by a lifelong passion for animals, Amy Toughey's journey from juggling three jobs with full-time study to working on cutting-edge dairy research trials shows what happens when hard work meets opportunity - and she's only just getting started.

National

Machinery & Products

JDLink Boost for NZ farms

Connectivity is widely recognised as one of the biggest challenges facing farmers, but it is now being overcome through the…

New generation Defender HD11

The all-new 2026 Can-Am Defender HD11 looks likely to raise the bar in the highly competitive side-by-side category.

» Latest Print Issues Online

Milking It

Buttery prize

OPINION: Westland Milk may have won the contract to supply butter to Costco NZ but Open Country Dairy is having…

Gene Bill rumours

OPINION: The Gene Technology Bill has divided the farming community with strong arguments on both the pros and cons of…

» Connect with Dairy News

» eNewsletter

Subscribe to our weekly newsletter