16 Dec 2021
Chris Gazey with his team

Leading the way in soil management

December 5, 2021 is World Soil Day and to celebrate, DPIRD’s Soil Science and Crop Nutrition Manager and SoilsWest co-Director Chris Gazey shared his insights across a long career in soil science with the Growers Group Alliance podcast. With more than 40 years’ industry experience, Chris reflects on some of the milestone findings throughout his career and where his team of 35 staff are currently devoting their resources.

No matter the soil type or individual constraints, Chris has been dedicated to finding techniques and solutions to see Western Australian grain growers maximise productivity, water and nutrient use efficiency.

In this episode you’ll learn about strategic soil renovation and the key learnings from comparison work done on soil acidity, from 2004/2006 and 2010/2012.

Chris also provides insight into plans for funding from the Department of Water and Environmental Regulation towards further soil sampling in the central wheatbelt.

If you’re interested in soil, this episode is a must listen.

Listen to the Podcast at the GGA website

24 Nov 2021
Social Media competition

World Soil Day Social Media Competition

World Soil day (5 December) is an international celebration of soils as the foundation for a healthy planet.

All through the week, we will be celebrating the vital role of soil in our ecosystem. Did you know that soils provide 98.7% of all calories consumed by humans? Or that soils store more organic carbon than the world’s atmosphere and vegetation combined?

To shine a light on the world beneath our feet, will be running a competition on Twitter.

For your chance to win a prize worth up to $500, simply tweet @soilswest using #WorldSoilDay2021 and tell the world why soil matters.

We will be keeping an eye open for the most original and engaging content on Twitter all through the week.

Looking for tips on how to get the edge over the competition? You can find handy hints on how to use to leverage social media for science communication in the Social Media for Scientists Workshop

22 Nov 2021

How does the price of phosphorus fertiliser influence net return in wheat?

Key Messages for growers

  • The level of yield response has a greater impact on economic returns than the cost of MAP.
  • A wide range of P rates will achieve the same net return at most of the case studies here.

With global phosphorus (P) supply chain issues continuing and prices for fertiliser expected to stay high in 2022, decisions around P fertiliser application rate will have greater influence on the budgets of grain-producing businesses than usual next season.

Higher prices for P fertilisers have prompted growers to question whether they should reduce rates to maximise economic returns from applying P. The answer depends on the level of yield response to P per hectare that is expected.

A current Grains Research and Development Corporation (GRDC) investment is assessing how soil properties and climate can influence yield response to P fertiliser in wheat. This research is in progress, however, completed field trials provide an opportunity to examine some economic case studies.

As part of this research, researchers are investigating what precision in P rates is required to maximise economic returns from P fertiliser. The calculations show the range of rates that maximise net return, referred to as the optimal range, shown below in Table 1

The impact of an increase in price for P fertiliser was assessed using three price scenarios for MAP: $700 per tonne (close to the five-year average), $1050 per tonne (1.5 x average) and $1400 per tonne (2 x average). The economic analysis was done for five sites that represent the range of responses observed, from very low to very high yield response to P. The price for wheat (allowing for delivery and levies) was set at its five-year average of $273/t.

The results show that the level of yield response to P has a greater influence on the optimal range than fertiliser price. For example, doubling the MAP price from $700/t to $1400/t shifted the optimal range from 20-55kg P/ha, to 11-56kg P/ha at Boyup Brook where a yield response of 2.27t/ha occurred. At Wandering, where a yield response to P of 0.65 t/ha occurred, the same increase in price shifted the optimal rate from 13-23kg P/ha to 6-22kg P/ha. The greatest shift in optimal range occurred at the Northam site, where a response to P of 0.38t/ha occurred; it decreased from 7-27kg P/ha to 2-11kg P/ha. At Tammin, where there was no significant yield response to P, the optimum rate was 0kg P/ha under all price scenarios.

Table 1: Summary of economic analysis for the case study trials.  n.s. = yield response not statistically significant.

Economically-optimum rate (kg P/ha)
Boyup Brook











Response  percentile 100th 75th 50th 25th 0
Yield response (t/ha) 2.27 0.97 0.65 0.38 n.s.
MAP price ($/Ha) Rate Range Rate Range Rate Range Rate Range - -
700 37 20-55 27 22-32 18 13-23 17 7-27 - -
1050 36 11-60 23 13-33 16 5-27 12 5-19 - -
1400 34 11-56 20 13-28 14 6-22 6 2-11 - -


The optimal range is quite wide in these cases studies as the rate-return relationship is flat across a wide range (see link for full details below). In fact, there is overlap in the optimal range for the three price scenarios. For example, at the Wandering site a P rate between 13 and 22 would fall within the optimal range for each price scenario.

The wide range of rates within the optimal range demonstrates that growers have flexibility to reduce financial risk without reducing profit. The optimal range at Boyup Brook and Brookton are above rates typically used in those areas – we’ll know more about how current practice compares to economic optimum when this research is complete. The optimal range at Tammin is unlikely to be used by growers; it’s more likely that growers will apply P at replacement rates in this scenario to maintain soil P fertility.

For more detail on the reduction in net return by applying P rates below the optimum range click here.

The field trials used as case studies here are from a series of trials where nitrogen, potassium and sulphur are applied to ensure only P is limiting. Adequate supply of nutrients other than P is important to capture economic benefit of applying P in your crops.

While these case studies provide an assessment of the sensitivity of the optimal range of rates to increases in MAP prices, they are not intended to provide recommendations. Soil testing for nutrients, in combination with assessing different price and yield scenarios are the best approach for determining the rate required for individual paddocks.

To see the full detail of the economic analysis for the case studies, click here.

This article was produced by the GRDC project ‘Increasing profit from N, P and K fertiliser inputs into the evolving cropping sequences in the Western Region’ (GRDC Project code: UWA1801-002RTX).

Field trials used for this work were established, funded and maintained by Summit Fertilizers and CSBP.

What do I lose by applying P rates below the optimum range?

The economic impact of applying P rates below the optimum range is dependent on the yield response to P (Figure 1). The potential for lost income is greatest at the Boyup Brook site, followed by Brookton, Wandering and Northam.

At Boyup Brook, the average reduction in net return between 10 and 19 kg P ha is $19/ha per kg of P. At Brookton, the average reduction between 10 and 21 kg P/ha is $5/ha per kg of P. At Wandering, the average reduction between 0 and 12 kg P / ha is approximately $8/ha per kg of P. At Northam, the average reduction between 0 and 7 kg P / ha is approximately $4/ha per kg of P.

Relationship between net return and P rate at levels below the optimum range

Figure 1: Relationship between net return and P rate at levels below the optimum range. Values within or above the optimum range not shown here.

Case Studies

Case Study 1 - Boyup Brook

Year 2020 Soil test data 0-10 cm
Crop Sceptre Wheat Colwell P (mg/kg) 74
Sowing date 22nd May PBI 395
OC (%) 4.9
pH (CaCl2) 5.5
Economically-optimum rate (kg P/ha)
MAP price Rate Range.
700 37 20 to 55
1050 35 11 to 60
1400 33 11 to 56

Optimal P rates for Case Study1 Boyup Brook

Case Study 2 - Brookton

Year 2020 Soil test data 0-10 cm
Crop Sceptre Wheat Colwell P (mg/kg) 19
Sowing date 26nd May PBI 11
OC (%) 0.6
pH (CaCl2) 5.7
Economically-optimum rate (kg P/ha)
MAP price Rate Range
700 27 22 to 32
1050 23 13 to 33
1400 20 13 to 28

Case study 2 Brookton


Case Study 3 - Wandering

Year 2020 Soil test data 0-10 cm
Crop Sceptre Wheat Colwell P (mg/kg) 35
Sowing date 18th May PBI 81
OC (%) 2.7
pH (CaCl2) 5.9
Economically-optimum rate  (kg P/ha)
MAP price Rate Range
700 18 13 to 23
1050 16 5 to 27
1400 14 6 to 22

Case Study 4 - Northam

Year 2020 Soil test data 0-10 cm
Crop Sceptre Wheat Colwell P (mg/kg) 37
Sowing date 28nd May PBI 37
OC (%) 1.3
pH (CaCl2) 4.9
Economically-optimum rate (kg P/ha)
MAP price Rate Range.
700 17 7 to 27
1050 12 5 to 19
1400 6 2 to 11

Case study 4 Northam

Case Study 5 - Tammin

Year 2020 Soil test data 0-10 cm
Crop Sceptre Wheat Colwell P (mg/kg) 22
Sowing date 16th May PBI 29
OC (%) 0.8
pH (CaCl2) 5.6
Economically-optimum rate (kg P/ha)
MAP price Lower Upper
700 0 4
1050 0 -
1400 0 -

Case Study 5 Tammin


10 Sep 2018

DPIRD soil nutrition project underway

The Department of Primary Industries and Regional Development (DPIRD) is leading the ‘Nutrient re-distribution and availability in ameliorated and cultivated soils in the Western Region’ project, announced earlier this year by the Grains Research and Development Corporation, which was also discussed in last quarters SoilsWest newsletter. The Department is also working with the University of Western Australia (UWA), Curtin University, Murdoch University, CSIRO and MapIQ to deliver the project. The field trials for this project are now underway at various sites across the state. The feature image shows DPIRD research officer Dr Craig Scanlan and a delegation of Australia’s leading soil scientists discussing the trial at Meckering.

Department plant nutritionist Dr. Craig Scanlan said “that the field trials established this year would help researchers gain a better understanding of the long-term effect of rotary spading and deep ripping on soil nutrient availability and the impact on yield responses to fertiliser. Specifically, the trial at Meckering will provide us with a better understanding of how deep ripping changes the yield response to nitrogen (N) applied this year and if it has any impact on the residual benefit of this N in 2019”.

Dr. Scanlan also advised “that another trial established at the department’s Badgingarra Research Facility has been designed to measure the effect of the type of crop residue buried by inversion tillage in 2019 on the grain yield response to nitrogen fertiliser. Further paddock scale wheat trials have also been set up this season to gain an insight into how the yield response to potassium (K) fertiliser varies spatially on ameliorated soils”.

The trials at Mingenew, Meckering and Esperance are being undertaken on paddocks where Controlled Traffic Farming (CTF) is being used. These paddocks are like massive field trials, where CTF is being used to accurately place the fertiliser treatments and measure the corresponding yield data.

Stephen Davies?

Image: Crop sown using precision guidance into previous stubble (Stephen Davies, DPIRD)

The variation in the yield response to the potassium treatments across the paddocks will be used to target areas for soil sampling, to investigate which soil factors are influencing the yield response to K fertiliser on ameliorated soils. As a result of this work, the department will be able to provide some guidance on how growers should be doing their soil testing on ameliorated soils.

The department’s research complements two other projects, one led by UWA on increasing profits from fertiliser inputs in a range of emerging crop sequences and the other by the CSIRO to improve soil sampling methods to better predict soil nutrient availability and supply. Together, the research projects will quantify how yield response to fertilisers in ameliorated soils compared to current no-till practice. The outcomes of this work will be used to update existing decision support systems for fertiliser use. For more information on the research work contact Dr Craig Scanlan.

25 May 2018

Increasing water use efficiency, grain yield and profit in a no-till system (Western Australia)

Conservation agriculture (no-till) cropping systems is considered by many to have improved soil health, timeliness of sowing, moisture conservation and resulted in higher grain yields. The key components of this system are full crop residue (stubble) retention, diverse rotations and minimal soil disturbance. However the recommendation for full residue retention is sometimes seen as a major constraint to the adoption of no-till, and increasingly the use of tillage to combat herbicide resistant weeds or non-wetting is employed by growers.

Dr Ken Flower (The University of Western Australia), in partnership with the Western Australian No-Tillage Farmers Association (WANTFA) and CSIRO, leads a long term research site established in 2006 at Cunderdin on an alkaline red sandy clay loam. The experiment which has co-investment from the Grains Research and Development Corporation (GRDC) aimed to determine the long term benefits of the key components of conservation agriculture and has shown that significant amounts of residue can build up through the removal of livestock from the system and no removal or burning of stubble. Using four different cropping philosophies i) cereal rotation, ii) diverse rotation, iii) control (monoculture wheat) and iv) ‘farmer’ rotation (cereal, cereal, break crop or fallow), a total of 11 crop sequences were established; and from 2010 a subset of plots had residue retained and spread behind harvester or were wind-rowed behind the harvester and burned, to consider the impact of stubble load on production.

Wind-rowing and burning were effective at decreasing residue levels by 40 to 60 per cent, with a variable influence on grain yield observed depending on crop residue type and amount. When there was relatively little cereal residue present after harvest (less than about 3 t/ha), retaining all the residue resulted in yield gains compared to where residues were reduced by wind-row burning; whereas, the opposite was true under greater stubble loads with higher yields from windrow burning.  By contrast, the effect of windrow burning of canola residue on the following wheat yield was small regardless of high residue levels.

Continuous wheat and the cereal rotation had the highest cumulative nine year average gross margins, despite higher grain protein and improving yields under a more diverse rotation. Lower gross margins in the diverse rotation were associated with poor legume performance in many years and low canola yields in dry seasons. Improving the reliability of these break crops in this growing environment is the key to increasing their uptake by farmers. Cover crops in the rotation generally negatively impacted gross margins.

At this relatively low rainfall site, with Mediterranean-type conditions, in south-western Western Australia, highest profitability came from having moderate residue amounts, in a rotation dominated by cereals and not including cover crops. The experiment will continue to inform longer term outcomes for production, weeds diseases and soil health. A recent publication can be found here. For further information please contact Dr Ken Flower (ken.flower@uwa.edu.au).

Image: Burnt windrow after Canola. Image attribution: Ken Flower, University of Western Australia

25 May 2018

Accessing Online Farm Trials Information

The Online Farm Trials (OFT) portal was initiated in 2013 as a co-investment between Federation University Australia (FedUni) and the Grains Research and Development Corporation (GRDC). The purpose of OFT is make the results of grains industry research trials and demonstration trials much more discoverable and publically assessable. The OFT team is led by FedUni Senior Research Fellow Dr Nathan Robinson and includes both social scientists and a great team of web developers at the Centre for Research and Digital Innovation (CERDI) at FedUni in Ballarat, Victoria. Main Image-The OFT team: Paul Freely, Julie Parker, Dr Ben Wills, Andrew Macleod, Dr Nathan Robinson

The primary function of the OFT tool is to maximise enduring profitability of the Australian grains industry by providing easy and ongoing access to grains related field trials research from across Australia. This is achieved via a publicly accessible, searchable and simple to use online database, supported by contributions from a wide range of collaborators and partnerships. Trials information contained in OFT includes both new and legacy trials, a significant portion of which have been funded by GRDC.

While to date key users of OFT have tended to be researchers and providers of agronomic advice, OFT now also provides collections of seasonally relevant trials aimed directly at growers.

The website features a self-service module which allows research organisations or individuals to upload and manage their data. An important aspect of this tool, is that the data ownership and accessibility is maintained by the contributor. Dr Robinson said that “one of the important features of the project is that control of the data stays with the data contributor, they can edit and remove data if they wish, they even have the ability to embargo the publication of data”.

Currently the portal hosts information on over 6600 trials, 85 per cent of which are publicly accessible. Data contributors to date include individuals, grower groups, farming systems groups, state government and private research providers, and universities.

Data can be extracted from the system in two primary forms. Either as a downloadable PDF copy of the research report, or additionally in some instances, numerical research data which allows for a graphical comparison between multiple trials. A key consideration going forward is data quality and comparability, and ensuring users of the system continue to access the maximum number of trials, while also being able to make informed decisions about the statistical robustness of any given trial and its suitability for their needs.

Image: Professor David Lamb from the Precision Agriculture Research Group at the University of New England using Online Farm Trials







To aid this continued development an expert advisory group has been convened, and includes representatives from a range of stakeholder groups, including; farmers, agronomists, university and public sector researchers, research managers and the GRDC. The panel is focusing on how to add value, including via the development of tools and functionality for currently active trials which will reduce the double handling of data. Additional planned developments include easy to understand data quality indicators to ensure that users of the portal are able to make informed decisions based on in-depth knowledge of the data quality characteristics of the research.

Organisations also have the opportunity to download an OFT ‘widget’, which is essentially a mini version of the OFT search engine, that can be embedded in other websites. The full OFT website can be accessed at www.farmtrials.com.au; and an example of the OFT widget can be viewed on the Soilswest website.

For more information about this project contact Dr Ben Wills (b.wills@federation.edu.au)

Image Attribution: Ms Julie Parker (CeRDi)

25 May 2018

Potassium nutrition on frost resistance in cereal crops

The role of potassium (K) in protecting crops from damage due to frosts has been alluded to for many years and has been mentioned in plant nutrition textbooks. In studies on other plant types (e.g. potatoes, carnations) potassium has been shown to mitigate potential plant damage from frost events. However little is known about the effect that various concentrations of potassium have in mitigating deleterious effects on plant sterility and yield for cereal crops in Western Australia, apart from some anecdotal reports that frost damage is greater for wheat grown in low potassium soils.

Potassium is critical for optimal plant growth from early establishment through to grain development. Regulating the opening and closing of leaf stomata during photosynthesis, potassium supply influences plant responses to both light and the uptake of carbon dioxide. The regulation of both water loss via the stomata and water uptake by the roots, means potassium also has a role in water management in the plant. Potassium also contributes to the synthesis of both protein and starch in the grain, which influence grain filling and quality.

Research by Murdoch University’s Dr Richard Bell and Dr Qifu Ma has recently been published identifying how potassium application could potentially alleviate floret sterility and loss of yield in wheat in Western Australia (Ma et al. 2018). The study was conducted to determine the impact of frost events on a cereal crop using the wheat cultivar Mace, with various applied potassium levels, on floret sterility and yield over two different growing seasons (2015 and 2016) at two different locations (Aldersyde and Beverley). The potassium treatments in 2015 were nil and 80 kg K/ha, in 2016 they were nil, 20, 40 and 80 kg K/ha. Frost events were determined to have occurred if air temperatures below 0°C were measured in the plant canopy or below 2°C measured by the onsite weather station. Frost events between July and October occurred on 24 days during 2015 and on 54 days during 2016.

Changes in frost susceptibility by potassium supply were measured and evaluated in terms of floret sterility, percentage reduction in grain numbers, anti-oxidative activity, net photosynthesis, leaf potassium concentrations, plant growth and grain yield. Yield results suggest that while improved plant potassium status can increase grain yield by between 10-20 per cent in wheat exposed to minor or moderate frost events (canopy temperature at 0 to -3 °C), there was no observed yield response under severe frost events (-4 to -6 °C). For more information or a copy of the paper “Potassium application alleviates grain sterility and increases yield of wheat (Triticum aestivum) in frost-prone Mediterranean-type climate” please contact Dr Richard Bell (R.Bell@murdoch.edu.au).

Image: Wheat heads with symptomatic signs of frost. Provided by Richard Bell, Murdoch University.

25 May 2018


The University of Western Australia (UWA) and Department of Primary Industries and Regional Development (DPIRD) have recently partnered in a Grains Research and Development Corporation (GRDC) co-investment with organisations from both the public and private sectors, to provide updated information on soil nutrient supply to Western Australian growers’ to improve profitability through more efficient nutrient use.

One node of the nutrient investment program led by Professor Daniel Murphy (UWA) has nitrogen (N) as its focal point. It will focus on understanding soil processes and how the timing and supply of soil N can be matched to various fertiliser strategies to provide the potential for the best return on investment from nitrogen fertiliser.

Professor Murphy said that “Water and N interactions are major drivers for plant growth and grain yield. Nitrogen is also a primary constituent of wheat protein, so sufficient soil N is an essential ingredient in meeting quality aspects of specific wheat grades” The uptake of N, is a factor influencing both early plant growth and yield potential, and later on in the growing cycling a remobilisation of N into the grain of the wheat affects final protein content.

Plants require more N than any other nutrient. The majority of N in soil originates from commercial fertilisers, soil organic matter, crop residues and animal manures. The release of mineral N from decomposition of organic matter is a significant source of N for grain crops in Australia. Although N can be added to soil in either inorganic or organic forms, plants take up only inorganic N and the other forms must be transformed prior to use. Nitrogen can be lost from the soil due to a number of processes and these include denitrification, volatilisation, leaching, crop removal and soil erosion/runoff.

With increasing climate variability and changes to growers’ cropping programs, the decision to determine when and where to apply N and at what rate has become more complex.  Growers’ N requirements are dependent on a number of major factors and include rainfall patterns as they unfold through the year, soil N supply, residual fertiliser N, logistics, and if economics are included, the price of N and the price of grain.

New research will focus on the residual benefit of organic and inorganic N on the following crop, with a focus on decision points for N management. It will investigate which components of the N cycle require a better understanding to improve the prediction of fertiliser N requirements. A component of the work will include using a stable isotope (15N; Nitrogen-15) technique to quantify specific N pathways in the soil.

Insights will be obtained via a series of laboratory, glasshouse and field experiments that investigate the N cycle, the impact of specific processes on plant available N supply, grain yield and profit response to fertiliser N. For example, there is considerable uncertainty about the rate of N required because yield potential is unknown at the time of planting and varies significantly within and across seasons due to soil and organic supply versus consumption. Soil mineral N can make up a large component of N supply to the crop; however, to our knowledge, there is no information on how wheat, barley and canola respond to different levels of soil mineral N at the same site.

Field experiments will determine whether wheat, barley and canola crops can effectively utilise soil derived N and examine crop specific responses to soil mineral N concentrations. Additional field experiments will also be undertaken to quantify the residual effects of crop sequence on the yield response to fertiliser N application. Identifying rotational sequences and management strategies that result in a run-down, steady-state or build-up of soil N will help in determining appropriate strategies to sustain productivity without running down the ‘bank’.

Data will be used to determine if refinements to the “Select Your Nitrogen” (SYN) model are required and the parameters for SYN optimised for data from current cropping systems, to provide a basis for economic analysis.

For more information contact Daniel Murphy (UWA, daniel.murphy@uwa.edu.au) or Craig Scanlan (DPIRD, craig.scanlan@dpird.wa.gov.au)

Photo:Daniel Murphy et al.; Image Attribution: UWA





04 Apr 2018


The University of Western Australia’s Professor Zed Rengel leads new research in soil phosphorus (P) supply as part of the new co-investment targeting better nutrient use efficiency. As fertiliser costs are one of the highest variable costs for grain producers in WA, and with changes in climate and farming systems in recent years, the scientific knowledge that underpins these P fertiliser management decisions needs to be updated.

Phosphorus is an essential element in several key plant structural compounds and is part of numerous enzymes. In grain crops, good P acquisition results in improved growth and development, increased resistance to plant diseases, stem strength, earlier crop maturity, enhanced flowering and seed production, and is also linked to increases in grain quality.

As with the other nutrients of interest, factors which influence the availability of P in soil includefertiliser application and crop removal, climate conditions and soil type. The amount of available P is determined by many specific factors including soil pH, iron and aluminium content, availability of other nutrients, clay content and type of clay, organic matter, soil temperature, soil aeration, soil moisture, soil compaction and also timing and placement of fertiliser application.

Soil P has accumulated across much of WA agricultural region, with a recent survey showing a large percentage of soils with soil P levels above the critical concentration that allows for 90% of maximum production to be achieved. With current fertiliser decisions being based on the premise of P deficiency, it is clear that P fertiliser management in local soils must change, but the current body of knowledge needed to implement this change is inadequate. In soils with sufficient P for example, Prof Rengel asks “How long can people farm with current drawdown rates of P and how does the rate of drawdown vary across soil types and under different cropping systems? These are some of the key questions that require answers”.

Together with industry partners CSBP and Summit who each contribute experimental sites to this project, the Department of Primary Industries and Regional Development and the University of Adelaide, future experiments will focus on identified research gaps as outlined.

  • Primer P – The seed has its own store of P but may benefit from an additional small priming application of P to increase root and shoot establishment and plant vigour. How much extra P (the primer amount) is required to assist the plant to achieve this optimally will be determined for wheat, canola and narrow-leaf lupins on soils that would historically have been considered P sufficient. Prof Mike McLaughlin (University of Adelaide) will co-supervise a PhD student that will undertake some of this work using P isotopes.
  • Drawdown – A certain amount of P, the drawdown quantity, is removed from the soil following harvest. The aim of this work will be to determine the amount of drawdown that occurs across a number of field sites over four seasons, allowing for different soil types, application rates of P and varying climate patterns. Determination of P drawdown rates can then inform the industry about the amount of P required annually to keep soil above the critical P threshold for that soil.
  • Subsoil P deficiency – Data suggest a large difference between the P content in the upper soil zone (0 to 10 cm) than deeper (below 10 cm) in the profile. In a large number of cases there is sufficient P in surface soil but a deficit in deeper layers. This is of particular interest because of changes to management practices where farmers are now mechanically mixing the soil via deep ripping, inclusion plates and spading for example. Quantifying the location and amount of P re-distributed down the profile will be one of many aspects considered in this project.

Knowledge gained from these programs will be used to communicate to the grains industry changes in nutrient management strategies and modelling of the economic responses to any new P management strategies undertaken to update nutrient decision guidelines. For more information contact Zed Rengel (zed.rengel@uwa.edu.au).

Photo:Zed Rengel (Image supplied by Zed Rengel)

resources :http://www.cropnutrition.com

04 Apr 2018


Providing updated information to improve WA grower profitability through more efficient nutrient use for nitrogen (N), phosphorous (P) and potassium (K) is a primary outcome for a recent co-investment between the Grains Research and Development Corporation (GRDC) and partnering organisations the Department of Primary Industries and Regional Development, University of Western Australia, Murdoch University and private sector partners.

Dr Craig Scanlan of the Department of Primary Industries and Regional Development leads the nutrient project, with Dr Elizabeth Petersen (UWA adjunct) and Dr Fiona Evans (Murdoch) undertaking the economic and sensitivity analyses for the project and working with research partners to update model parameters. At the outset of this comprehensive investigation, stage one of the economic analyses and reporting will be completed by the end of this year and will focus on N.

To determine the most economically viable N application rates for a specific farm or paddock (depending on the scale of interest), an economic model is usually used that includes information on how responsive a site may be to fertiliser application. Suggested fertiliser application rates are determined based on a number of parameters and inputs, and can be dependent on which model is being used. A component of this project is to review and benchmark the performance of “Select Your Nitrogen” (SYN) by comparing predicted versus actual yield as well as grain quality (e.g. protein, oil) response where appropriate for a variety of crop types including barley, canola, lupins and wheat in recent, current or proposed field experiments.

Under investigation will be the sensitivity of model inputs and parameters on the numerical output of the model (the economically optimal rate of N), as well as the uncertainty (error) of the model inputs and how this also affects the output of the model.

Dr Petersen explains that “With increasing climate variability and changing sowing patterns, a grower’s decision regarding when to apply N and at what rate is becoming more complex. Nitrogen requirements depend on rainfall patterns as they unfold through the year, soil N supply, residue N, the price of N and the price of grain. Our research will be considering what factors most effect the economically optimal rate of nitrogen to help prioritise future research work into components of the N cycle.”

Ultimately the goal is to quantify the overall precision of the model, so that the model output is accurate to achieve profit targets for growers. For example, 90% probability of exceeding a return on investment of greater than 2:1.

Photo: Liz Petersen; Image attribution: Bruce Petersen