Guidelines for organic amendment experiments to enable attribution of yield to plant nutrition or soil amelioration

Corinne Celestina1, James Hunt1, Ashley Franks2

1 Department of Animal, Plant and Soil Sciences, AgriBio the Centre for AgriBiosciences, La Trobe University, Bundoora VIC 3086,,
2 Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora VIC 3086


Organic amendments such as manures, composts and plant residues are often used as alternatives to inorganic fertilisers or to ameliorate physicochemical soil constraints. Crop yield responses to the application of organic amendments could be due to plant nutrients contained in the amendment, the amelioration of (sub)soil constraints, or some combination of both factors. However, if experiments are designed incorrectly these factors can be confounded, leading to difficulties in accurately ascribing yield responses to nutrition or amelioration. We suggest guidelines for design, conduct and analysis of organic amendment experiments which will allow the correct attribution of yield responses. These include: identifying genuine soil constraints, selecting proper control treatments, and using appropriate sampling protocols to assess treatment differences.

Long term impacts on crop productivity following amelioration of a sandy soil

Melissa Fraser1, Nigel Wilhelm2 and David Davenport3

1 Primary Industries and Regions South Australia (PIRSA), 74 Struan House Rd, Naracoorte, SA, 5271,,
2 South Australian Research and Development Institute, PIRSA, Urrbrae, SA, 5064,
3 PIRSA, Port Lincoln, SA, 5606


Crop water-use on sandy soils is often poor with productivity constrained by the presence of water repellence, compaction, low water holding capacity and/or poor nutrient and biological fertility. Treatments that addressed these constraints were applied in a field trial on the Eyre Peninsula in 2014. Crop responses and changes in soil fertility have been measured. Physically mixing the soil to 0.3 m by spading was beneficial on this sand; yield responses in the order of 70 to 100 % were seen in 2018, five years after treatments were applied (unmodified control = 2.35 t/ha); further yield increases in the first two years were obtained with the incorporation of lucerne hay in the spading operation.

Similar results were seen in comparable trials in the Murray Mallee and South East of SA, confirming that crop performance on sandy soils can be substantially improved when their inherent constraints are addressed. Understanding the nature and interaction of the constraints is vital to identify the optimum amelioration strategy.

Organic amendments and lentil growth in Mallee soils

Mitchell Fromm1, Jason Brand1, Audrey Delahunty2, James Nuttall1

1 Agriculture Victoria, 110 Natimuk Road, Horsham, Victoria, 3400,, 2 Agriculture Victoria, Cnr Eleventh St & Koorlong Ave, Irymple, Victoria 3498


Lentil production in the Victorian Mallee has been increasing at a rapid rate due to improved adaptation of lentil cultivars to dry environments and the rotational and financial benefits this crop provides.  Dune swale systems cover a large portion of cropping area in the region, where lighter textured (sandy) soils can be infertile and inherently lower yielding. Increased organic carbon improves soil fertility and can be enhanced through the addition of organic amendments such as poultry or pig litter or potentially almond hulls.  This study assessed the response of lentils to poultry litter, almond hulls and standard fertiliser across three soil types from the Victorian Mallee environment.  The glasshouse trial showed that poultry litter provided the greatest yield increase and stability across the three soil types compared to fertiliser, where increases were 6, 29 and 24% for swale, mid slope and dune soils respectively.  Where almond hull was applied, yield was consistently lower than for fertiliser across respective soil types.  Importantly these results highlight the value of poultry litter increasing the productivity of sand dune type soils to the equivalent productivity of the heavier swale soil type.  Further work is required to assess the long-term benefits and the practicality of using such amendments in a large-scale farming context.

Agronomic options to overcome soil water repellence improve crop performance regardless of sowing conditions in a gravelly duplex soil

G.P. McDonald1, S.L. Davies2, D.M. Bakker1, G. Poulish1

1 Department of Primary Industries and Regional Development, 444 Albany Highway, Albany, WA, 6330,,, 
2 Department of Primary Industries and Regional Development, 20 Gregory St, Geraldton, WA, 6530


Soil water repellence (SWR) is a significant constraint to crop establishment in South-West Western Australia (WA). A long term agronomic experiment commenced in 2015 to investigate a range of potential amelioration and mitigation options to manage SWR. All treatments improved crop establishment and yield by varying amounts over four seasons. The most effective treatments for improving yield were strategic deep tillage and banded wetting agents. Strategic deep tillage via mouldboard plough (MBP) or one-way plough (OWP) improved yield in all seasons regardless of rainfall patterns. The application of pre-emergent herbicides on strategic deep tillage treatments trended towards reduced crop growth and yield but rarely to a significant level. Near-row sowing increased plant establishment in two of the four seasons but yield improvements in these seasons were significantly lower than almost all other treatments. Improved crop performance from wetting agent techniques occurred only in years with dry soil conditions at sowing. Wetting agents were proven to be a good short term option for water repellent soils but strategic deep tillage provided the most consistent longer term yield improvement across all the growing seasons experienced.

A field method to assist selection of wheat varieties best suited to local soils may be the best strategy for mitigating waterlogging risk.

Sam North1, Carlos Ballester Lurbe2, James Brinkhoff2 and Alex Schulz1

1 NSW DPI, 449 Charlotte St, Deniliquin, NSW, 2710, website, Email, 
2 Centre for Regional and Rural Futures (CeRRF), Deakin University, Research Station Rd, Hanwood, NSW, 2680


Waterlogging is a major constraint to wheat yields in Australia. There is genetic diversity for waterlogging tolerance in wheat and there is a need to improve wheat yields on waterlogging prone soils through identification of more tolerant varieties. This study aimed to (i) assess the usefulness of redox potential (Eh) and canopy temperature (Tc) to explain wheat responses to waterlogging and; (ii) determine whether there is sufficient variability in current, commercially available wheat varieties to justify trials on local, waterlogging prone soils. Ten varieties were examined, with control and waterlogged treatments imposed at two sites. Waterlogging was imposed at anthesis, with water ponded on plots for 14 days. Measurement of Eh allowed differences in the responses of varieties to waterlogging at the two sites to be understood. Canopy temperature was also useful at showing differences between the varieties. There were clear differences in the responses of currently recommended wheat varieties to both soil type and to waterlogging. Local trials on waterlogging prone soils are needed to allow wheat growers to select the best varieties for their soils.


Low-risk management strategies for crop production on water repellent sands

Phil Ward1, Nigel Wilhelm2, Margaret Roper1, Terry Blacker3, Ramona Kerr1, Priya Krishnamurthy1, Ian Richter4, Shayne Micin1

1 CSIRO, Private Bag No 5, Wembley WA 6913;,
2 SARDI-PIRSA, Waite Research Precinct, Hartley Grove, Urrbrae SA 5064,
3 SARDI, 119 Verran Tce, Port Lincoln SA, 5606,
4 PIRSA, 226 McKenzie Rd, Minnipa SA 5654,


Water repellent (non-wetting) soils pose significant problems for crop production and natural resource management in southern Australia. Water infiltration is patchy, and the resulting impacts on crop and weed germination can reduce yields by more than 50%. In this research, we compared the impacts of two wetting agents and near-row sowing as low-cost strategies to improve crop emergence and yield. A randomised block trial with 4 replicates was established on a sandy soil near Wharminda on the Eyre Peninsula in SA. Wetting agents improved crop emergence in wheat (2015: 47-58%), barley (2016: 44-111%) and lupins (2017: 210-326%), and increased grain yield in 2015 (26-31%) and 2017 (26-70%) but had no impact in 2016. Near-row sowing had no significant impact on either emergence or crop yields. Neither wetting agents nor near-row sowing had any direct impact on severity of soil water repellence.

Effects of deep ripping on soil compaction and crop performance in Mallee sands

Brian Dzoma1, Nigel Wilhelm2, Peter Telfer3 and Kym Zeppel1

1SARDI Loxton Research Centre. P O Box 411, Loxton SA, 5333,
2SARDI Waite Research Precinct. Building 11A Hartley Grove, Urrbrae, SA 5064,
3Turretfield Research Centre. Holland Road, Rosedale, SA 5350


Soil compaction on sandy soils is one of the major problems facing modern farming systems because of frequent use of heavy machinery which comes with intensive cropping. Deep ripping on Mallee sands is becoming a common option to reduce hard pans and ameliorate compacted layers. The challenge facing growers is determining the optimal ripping depth and tine spacing for their soils.  Aims of this project were to assess the impact of deep ripping on subsoil compaction and performance of several crop species and to determine the optimal ripping depth x tine spacing for Mallee sands. Our trials showed that ameliorating compacted sandy soils in low rainfall environments can lead to improved shoot DM and grain yield, and should subsequently lift farm productivity and profitability. In terms of grain yield, ripping at narrow or wide tine spacing gave similar outcomes and wider tine spacings can therefore be considered in order to use less machinery horsepower. Our trials also show that when the soil in question is compacted to depths beyond 40cm, then ripping deeper is better for grain yield, provided there are no other chemical constraints below the compaction zone.

Promoting soil health in dryland agriculture by increasing cropping intensity

Alwyn Williams1, Lindsay W. Bell2

1 School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD 4343,,
2 CSIRO, 203 Tor Street, Toowoomba, QLD 4350


Extended fallow periods are implemented in dryland cropping systems to allow recharge of soil moisture for the subsequent crop. Over time, fallow periods deplete soil carbon (C), a foundation of soil health that affects soil microbial activity and the long-term capacity of soils to store moisture. Reducing fallow periods by increasing cropping intensity (e.g. cover or double cropping) can promote soil health and thereby contribute to the long-term sustainability of dryland cropping systems. However, the agronomic feasibility of increasing cropping intensity in dryland systems is unknown. Using a cropping systems experiment in southeast Queensland, we investigated the impacts of cover and double cropping on indicators of soil health and sorghum grain yields in comparison to conventional fallow-based cereal production systems. Both cover and double cropping systems increased concentrations of soil C compared with the conventional systems. In the cover crop system, this was associated with greater soil microbial activity and improved surface soil moisture storage at crop establishment. Additionally, sorghum grain yield in the cover crop system did not differ significantly from those in the conventional systems. In contrast, the double crop system depleted soil moisture reserves leading to dramatic yield loss as well as reduced nitrogen- and water-use efficiency. Our results demonstrate that reducing fallow periods via cover cropping is a potentially feasible method for promoting soil health in subtropical dryland cropping systems. Longer-term research is required to determine the trade-offs and tipping points associated with the use of cover crops in drylands.

Addressing subsoil acidity in the field with deep liming and organic amendments: Research update for a long-term experiment

Guangdi Li1,3, Richard Hayes1,3, Jason Condon1,2,3, Sergio Moroni2,3, Ehsan Tavakkoli1,3, Helen Burns1, Richard Lowrie1, Adam Lowrie1, Graeme Poile1, Albert Oates1, Andrew Price1 and Alek Zander2

1 NSW Department of Primary Industries, Pine Gully Road, Wagga Wagga, NSW 2650,,,
2 Charles Sturt University, Boorooma Street, Wagga Wagga, NSW 2650,
3 Graham Centre for Agricultural Innovation, Albert Pugsley Place, Wagga Wagga, NSW 2650


A long-term field experiment was established in 2016 to manage subsurface soil acidity through innovative amelioration methods with the aim to increase productivity, profitability and sustainability. Deep placement of lime increased soil pH and reduced exchangeable Al% at the depth where lime was placed, but there was no evidence to show vertical alkalinity movement during the first 3 years of the experiment.  Deep placement of lucerne pellets did not increase soil pH as much as expected, but reduced exchangeable Al%. Significant yield improvement was recorded from deep placement of lucerne pellets in a wet year (2016) but not in dry years experienced in 2017 and 2018, although large amount of mineral nitrogen was measured in autumn in 2017. Crop performance and soil chemical, physical and biological properties will be continually monitored to understand plant-soil interactions, the factors driving the differences in crop response to various treatments, and the long-term residual value of soil amendments.


The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

Photo Credits

David Marland Photography Graham Centre for Agricultural Innovation, Charles Sturt University

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