Potassium Newsheet   Vol 2 Iss 1 : Summer 2003

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SA: K deficiency confirmed in northern cropping regions 

A trial site established in 2002 at Laura by the South Australian Research and Development Institute (SARDI) has confirmed that K deficiency could be severely limiting yields on some South Australian soil types.  The possibility of K deficiency in South Australia's dryland cropping regions was raised by private agronomist, Stuart Roennfeldt who recognized deficiency symptoms in several cereal crops in 2001, which was confirmed by soil and plant analyses.  

Subsequently Stuart, and Nigel Wilhelm from SARDI, established the Laura trial site to confirm the diagnosis, to quantify the impact of K deficiency on crop yields and to investigate the options for fertilizer application.  In 2002, wheat yield at the site was increased from 0.5t/ha to 2.5t/ha with K application, and at the same time grain screenings were reduced from 12% to 7%.  In the 2002 season, banding K fertilizers below the seed at planting was more effective than broadcasting either before planting or mid-season.  The site is being monitored again in 2003 to quantify the residual value of K fertilisers.

Results from the trial site are summarised in a short article available on the Potassium in Agriculture website by clicking here.  For more information contact Nigel Wilhelm by email or on (08) 8303 9353. 

Can dietary K in late lactation improve bone redeposition in dairy cows?

Pastures which are high in K have been considered a problem in dairy systems because of the potential to increase the risk of milk fever in calving cows.  However, recent thinking suggests that K-rich pastures may play a role in preventing milk fever if utilized at a different stage in the lactation.  Work has recently begun at the University of Sydney's Camden facility to test the hypothesis that increased dietary K in late lactation, but no later than two weeks before calving, can encourage the re-deposition of bone, therefore increasing bone density at calving and subsequently reducing the risk of milk fever.  It is also possible that improving bone re-deposition between lactations may also lengthen the productive life of animals.  

PhD student Marie Bhanugopan, under the supervision of Dr David McNeill has initiated research to investigate the impact of high and low K diets during late lactation by measuring in-situ bone density at calving and the subsequent impact on blood Ca status and milk production.  For more information on this research contact David McNeill on (02) 4655 0633 or by email.  

Audit review of nutrient concentration in agricultural produce is available on Potassium website

As part of the National Land and Water Resources Audit completed in 2001, an assessment was made of the farm-gate nutrient balance of Australian agricultural systems.  In order to calculate the amount of nutrient removed from the farm-gate in produce, Drs Doug Reuter (CSIRO) and Geoff Judson (SARDI) undertook a comprehensive review of published and unpublished literature reporting the nutrient concentration of a wide range of agricultural products.

The results of this review are now available in the Research section of the Potassium in Agriculture website.  It is possible to view both the final list of nutrient concentrations used to calculate nutrient balances for the Audit, as well as accessing the complete set of references identified in the review.  The reported concentration values for a wide range of grains, oilseeds, fruits, vegetables, nuts and livestock products are presented in a tabular format.  This information may also be useful for calculating nutrient budgets on a regional or individual farm basis.  To search the Nutrient Concentration database on the Potassium website click here, or for more information about the National Land and Water Resources Audit and its results, visit the Audit website. 

VIC: Windrow effects show up in cereals near Hamilton

A banded or 'wave' effect, corresponding to the trash windrows of previous crops has appeared in numerous fields in the Western Districts of Victoria this season.  Experience in Western Australia has shown that this effect is often related to a depletion of soil K reserves and the concentration of remaining K in the windrow areas resulting in poor crop growth in off-windrow areas and better growth in on-windrow areas (see article).  

Private Agronomist Craig Henson, based in Hamilton, recognized the effect as a symptom of K deficiency despite the fact that several of the fields had been soil tested at 120 mg/kg of Colwell K.  Hi-Fert research agronomist, Andrew Speirs has also seen numerous examples of the windrow effect in crops in western Victoria and suggests that the best method of diagnosing the problem is to sample and analyse Youngest Emerged Blades (YEB) from good and bad areas separately.  

While Craig has undertaken strip trials at Hamilton which have shown a spectacular effect of top-dressed K at early tillering, his priority is developing options for applying K fertilisers to these fields next year.   For more information about the crop symptoms contact Craig Henson on 0427 554 968 or by email.  Dry matter, grain yield and plant nutrient concentration results from the replicated topdressed strips will be reported in the Potassium Newsheet when they become available.   

Fertilizer industry accreditation system to be introduced in 2004

In October, the Fertilizer Industry Federation of Australia (FIFA) launched an Eco-efficiency agreement with the Federal Government.  One of the key initiatives which will contribute to meeting the agreement is the development of the FERTCARE® product stewardship program.  FERTCARE® is a national education and accreditation program developed by FIFA and the Australian Fertilizer Services Association with the support of the National Heritage Trust.  It aims to improve the understanding of soil health and plant nutrition and to prescribe a level of competency required for the provision of information on the environmentally responsible use of fertilizers.

Three levels of accreditation will exist: Level A is for transport, storage and application service providers, Level B is for sales staff and staff in related agricultural and environmental roles in government and research institutions who may provide basic advice on fertiliser use, and Level C is for crop and pasture nutrition advisers and consultants who interpret soil analyses and prepare nutrient management plans.

The FERTCARE® accreditation scheme will recognize existing levels of competency but will also provide training and assessment opportunities in order to meet the standards required by each level.  A number of pilot groups will undertake training and assessment at Level B in November, with a rollout of the scheme expected in early 2004.  While the FERTCARE® program specifically addresses environmentally responsible fertiliser use, it also considers productivity issues and is a valuable training program for anyone involved in fertilizer sales, advice or logistics.  For more information on the FERTCARE® product stewardship program or FERTCARE® accreditation contact FIFA by email or on (02) 6230 6987.  

K Questions

Answers to recently posed questions on K nutrition:

A farmer asks: "What's the difference between red and white potash?"

Answer:   The most common potassium fertilizer, muriate of potash, can come as granules which are pinky-red or white.  Both sources come from naturally occurring mineral deposits that were precipitated when ancient shallow seas evaporated.  The deposits usually contain minor amounts of iron impurities, lending the ore a pinkish colour.  

The difference in colour of the final product arises due to differences in extraction techniques at different processing facilities.  With red potash, mined ore is crushed and put into a fluid suspension in which potassium chloride floats to the surface, is skimmed off, dried and screened.  White potash is produced by dissolving the ore under pressure in a hot brine.  Potassium chloride is precipitated as the brine cools and pressure reduces.  This second process also removes the very small amounts of iron impurities and therefore the red colour.

There is no agronomic difference between red and white potash due to its colour.  Both are equally soluble and contain comparable amounts of potassium and chloride.  However, some fertilizer handlers prefer to use red potash because it is easily recognisable and easily distinguished from other products, especially in blends.  

There may be differences in product handling characteristics between different potash producers that also happen to use differing extraction techniques, however these are not a result of the product colour.  

Recently published papers

Recently published scientific papers examining issues of potassium nutrition are listed below.   A searchable database of abstracts of scientific papers addressing issues of potassium nutrition is available on the Potassium in Agriculture website, where links to the home pages of relevant journals are also provided for anyone wishing to purchase full copies of individual papers.

Appel, C, Ma, LQ, Rhue, RD, and Reve, W.  (2003) Selectivities of potassium-calcium and potassium-lead exchange in two tropical soils.  Soil Science Society of America Journal  67: 1707-1714.

Borges, R and Mallarino, A.  (2003)  Broadcast and deep-band placement of phosphorus and potassium for soybean managed with ridge tillage.  Soil Science Society of America Journal  67: 1920-1927

Escudey, M, Diaz, P, Forster, JE, Pizrro, C, Beltran, L and Galindo, G. (2002) Prediction of K-Ca-Mg ternary exchange from binary isotherms in volcanic soils using the Rothmund-Kornfeld approach.  Australian Journal of Soil Science  40 (5): 781-790

Liu, Fan, Gilkes, RJ, Hart, RD and Bruand, A.  (2002).  Differences in potassium forms between cutans and adjacent soil matrix in a Grey Clay Soil  Geoderma  106 (3-4): 289-303

McNeill, DM, Roche, JR, McLauchlan, BP and Stockdale, CR.  (2002).  Nutritional strategies for the prevention of hypocalcaemia at calving for dairy cows in pasture-based systems.  Australian Journal of Agricultural Research   45: 113-122

Surapaneni, A, Tillman, RW, Kirkman, JH and Gregg, PEH.  (2002).  Potassium-supplying power of selected Pallic soils of New Zealand 1. Pot trial study.  New Zealand Journal of Agricultural Research  45: 113-122

Surapaneni, A, Tillman, RW, Kirkman, JH and Gregg, PEH.  (2002).  Potassium-supplying power of selected Pallic soils of New Zealand 2. Soil testing procedures.  New Zealand Journal of Agricultural Research  45: 123-128

Surapaneni, A, Palmer, AS, Tillman, RW, Kirkman, JH and Gregg, PEH.  (2002).  The mineralogy and potassium supplying power of some loessial and related soils of New Zealand.  Geoderma  110 (3-4): 191-204

Schneider, A.  (2003).  Characterisation of soil potassium supply as derived from sorption-desorption experiments.  Plant and Soil  110 (3-4): 191-204

The Potassium Newsheet is part of the wider Potassium Development program which provides agronomic information on potassium nutrition of crops and pastures through publications, workshops and a website. The program also supports research and development into the best management practices for potassium fertilizer use in Australian and New Zealand agricultural production systems.

At the Laura trial site, wheat growth at tillering was visibly improved by the application of K fertilisers (0 v 100 kg K/ha)

In This Issue:

SA: K deficiency confirmed in northern cropping regions

Can dietary K in late lactation improve bone re-deposition in dairy cows?

Review of nutrient concentration of agricultural produce is available on web

Victoria: Windrow effects show up in Western Districts cereal crops  

Fertiliser industry developing accreditation program 

K Questions

Recently published papers

Agronomist Craig Henson in a field of wheat near Hamilton, Victoria which has displayed marked windrow effects and responded dramatically to strips of topdressed MOP. Click on photo for an enlargement.

Muriate of potash comes in various grades and colours depending on the method of processing.