More profitable crops on highly calcareous soils by improving early vigour and overcoming soil constraints

Outcomes will be modified agronomic practices and improved soil conditions which increase WUE of crops and farm profitability as well as improved knowledge of the impact of high carbonate on crop performance.

Highly calcareous soils challenge crop production with a range of constraints and this limits the effectiveness of improved agronomic practices. Early crop vigour is poor and crop production continues to be limited to very low nitrogen and water use efficiencies.

This project, “More profitable crops on highly calcareous soils by improving early vigour and overcoming soil constraints” is supported by the Cooperative Research Centre for High Performance Soils and GRDC. The project aims to overcome constraints on these difficult soils in order to improve crop production, using a multi-disciplinary team of researchers from SARDI, Rural Solutions and NSW DPI.  There is also a complementary project, “Understanding constraints to crop profits on highly calcareous soils,” which is also funded by GRDC and is run by CSIRO which works closely with the CRC project.

What we’ve learnt in 2 years 

Highly calcareous soils are important in some areas of south-eastern Australia and challenge crop production with a range of constraints. The project, “More profitable crops on highly calcareous soils by improving early vigour and overcoming soil constraints”, supported by the CRC for High Performance Soils and GRDC, sought to identify and overcome constraints on these difficult soils in order to improve crop production. This was achieved through a multi-disciplinary team of researchers from SARDI, CSIRO and NSW DPI.  

Since its inception in 2020, a holistic approach to addressing these constraints to crop productivity and profitability was implemented to better understand: 

• The benefits of organic matter and extra nutrient inputs on crop health and growth
• The impacts of a range of amendments on subsoil properties typical of calcarosols 
• The contribution of novel approaches (carbon coated minerals – CCM (formerly bespoke biochar) to P supply, crop vigour and root health 
• Current issues with crop emergence and fertiliser toxicity under marginal moisture conditions, and 
• The impact of high soil strength and the contribution of a physical intervention to ameliorate compaction. 

Outcomes  

• Crops growing on a mildly calcareous soil were less responsive to the strategies investigated than those on highly calcareous soils of upper EP.  
• Short-term topsoil strategies resulted in better gains in crop biomass and yield when compared to longer-term subsoil strategies. 
• Higher seeding rates and adequate nutrition at sowing was effective at achieving high plant densities, crop biomass and grain yield. 
• CCM in the topsoil improved cereal crop vigour, biomass and grain yield as well as providing good benefits into the second crop. 
• High soil strength is an issue in calcareous soils, however, positive responses to deep ripping are less likely and usually limited by the hostile subsoil. 

Implications to industry 

Cereal crop responses to the more costly subsoil strategies were smaller and less likely in highly calcareous soils with underlying physical, biological, and chemical constraints. Ameliorating high soil strength by deep ripping has proven to be less effective on these types of soils than on other sands. The incorporation of organic amendments (pelleted chicken manure, CCM) into subsoils has shown potential to improve crop production but is still economically dubious. However, this response needs to be validated over more situations to determine their general impact on longer-term crop productivity and profitability. 

Plant population, crop biomass and grain yield were improved by higher sowing rates, providing that the denser plant populations are supported by improved nutrition (N and P and trace elements). CCM boosted crop vigour and biomass production when placed just below the seed. We suggest that at least part of the benefits from this CCM is to deliver P to the crop in a more effective way than current mineral fertilisers. Residual benefits of CCM were evident, however, further investigation is needed to determine how best to apply CCM and how low they can be applied to improve crop growth, productivity, and overall farm profitability.  

Key recommendations after two years of results are: 

1. Crop responses to the more costly subsoil strategies are smaller and less likely in highly calcareous soils with underlying physical, biological and chemical constraints. Therefore, the focus should be on short-term topsoil strategies to improve early crop vigour, biomass and grain yield. 

1. The use of higher sowing rates is an effective strategy to improve plant population, crop biomass and grain yield, providing that the denser plant populations are supported by improved nutrition (N and P and trace elements). 

1. Carbon-coated minerals placed just below the seed is another effective strategy to improve early crop vigour, biomass and grain yield. Residual benefits were very good. Further investigations are needed to fully define their residual benefits, determine how best to apply them and how low they can be applied to improve crop growth and productivity. This product is not commercially available.  

1. Ameliorating high soil strength by deep ripping has proven to be less effective on these types of soils than on other sands, therefore the recommendation is to identify and understand the underlying subsoil constraints before making the decision to deep rip.  

Addressing multiple constraints in calcareous soils using integrated solutions will ensure an increase in crop productivity and subsequently profitable and sustainable farming systems. 

Since its inception in 2020, the project has undertaken research trials (Poochera, Minnipa, Port Kenny) investigating innovative physical and chemical approaches to improving soil fertility and crop production. These approaches include deep placement of nutrients and amendments, activated and/or nutrient enriched organic matter and chemical amendments to manipulate pH and redox potential.

Fig. 1 Minnipa topsoil trial: 4 August 2021

*2 Zn, 3 Mn, 1 Cu (kg/ha)

The first year of field trials showed that some of the strategies have great potential to improve early and flowering crop biomass and final grain yield. For example :

• Bespoke biochar and Neutrog incorporated into the subsoil improved both crop biomass and grain yield in the first year of implementation.
• Bespoke biochar (Fig. 1) or a high seeding rate with adequate nutrition have also shown potential to improve crop yield when considered as a lower cost topsoil strategy.
• High plant densities and early crop cover can be simply achieved on highly calcareous soils by using higher seeding rates.
• A beneficial deep ripping response is unlikely in these calcareous soils because multiple subsoil constraints are usually present.
• A strategy of multiple applications of phosphorus performed well at Minnipa which suggests that poor P nutrition continues to be a constraint on these soils.
• Current fungicide options for suppressing rhizoctonia continue to perform poorly in these soils.

All three sites will be resown in 2022 to a Clearfield® barley, and a few new topsoil strategies will also be investigated. Detailed results are available in the article “More profitable crops on highly calcareous soils by improving early vigour and overcoming soil constraints” in the Eyre Peninsula Farming Systems Summary 2021.

Calcareous soils project update April 2021

Three field sites on upper EP have been selected and confirmed by sampling to depth for soil chemistry.  The two sites at Pt Kenny and Poochera are very highly calcareous to depth.  The Minnipa site is more typical of heavier soils in mallee environments with salinity and boron toxicity at depth (both common features in heavier mallee soils). Two trials will be conducted at each EP site, one focussed on topsoil issues, the other on subsoil constraints.  Both trials at each site will have treatments with packages of strategies to test their combined impacts.

Topsoil treatments will include different fertiliser packages, rhizoctonia control options, wetters, cultivation, sowing rate, additives such as biochar and mixes of several treatments. Subsoil treatments will include deep ripping with and without inclusion plates, with and without various soil amendments.

Two complimentary projects have been funded by the Cooperative Research Centre for High Performance Soils (Soil CRC) and the Grains Research and Development Corporation (GRDC) to investigate limitations to crop growth on highly calcareous soils of upper Eyre Peninsula so that strategies can be developed to overcome them.  These projects, which run through until 2023, will be delivered by research teams from the South Australian Department of Primary Industries and Regions (PIRSA), New South Wales Department of Primary Industries (NSW DPI) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) with support from Ag Innovation and Research Eyre Peninsula (AIR EP) and the MacKillop Farm Management Group (based in the south-east of SA).

Very highly calcareous soils from upper EP have been supplied to the NSWDPI team for controlled environment studies. The first study with subsoil from Poochera suggests that application of iron minerals (particularly goethite) can effectively stabilize root exudates and soil organic carbon (SOC) in plant systems. This may help build SOC storage and consequently improve soil productivity.  A 2-year experiment is about to be started to quantify the rates and magnitude of co-application of biochar and reactive iron on plant residue carbon and SOC stabilization in a calcarosol to understand the underlying biotic and abiotic mechanisms.

A bespoke biochar formulation to be included in 2021 SA field trials was developed and tested in pot experiments. The best amendment was selected and synthesis of 1.5 tonne of this formulation is underway.

Results of demonstration trial at Poochera in 2020

Barley grew and yielded poorly, with severe rhizoctonia, unless deep ripping had occurred prior to seeding.  Agronomic packages which were selected to reduce rhizoctonia and to cause fertiliser toxicity in seed rows did not reduce rhizoctonia nor result in obvious toxicity, which highlights the uncertainties with crop production on these soils in that environment.

Deep ripping improved crop growth all season and resulted in a 30% increase in grain yield (0.3 t/ha). Incorporating animal manure to amend subsoil conditions had little impact on barley growth but incorporating nutrient-enriched biochar to depth improved the crop all season but did not increase grain yield.

This trial will be maintained for the remaining two seasons of the project, using a crop compatible with the rest of the paddock.

Acknowledgements

This project, “More profitable crops on highly calcareous soils by improving early vigour and overcoming soil constraints” is supported by the Cooperative Research Centre for High Performance Soils whose activities are funded by the Australian Government’s Cooperative Research Centre Program and GRDC. The authors would also like to thank the landholders and families involved in this project: Shard Gosling, Simon Guerin and the Minnipa Agricultural Centre. 

For more information, please contact:

Brian Dzoma (SARDI)

M: 0455 071 032 | Email: brian.dzoma@sa.gov.au