Alternative fertiliser pasture study findings published
Fiona Leech, Senior Agriculture Advisor, Yass.
Alternative fertiliser products are commonly promoted for use on pastures as a means to improve pasture productivity and support a more ‘healthy’ soil microbial environment. However, minimal field research has been conducted to validate such claims. A six year study (2009 – 2014) was conducted on phosphorus (P) deficient soils at three sites near Yass, NSW, to investigate the effect of top-dressing typical native perennial grass-based pastures with a range of alternative fertilisers and with single superphosphate.
- The results showed minimal influence of alternative fertilisers on highly resilient soil microbial communities.
- Farmers should continue to use economic rationales associated with pasture productivity response to guide their decision making around the choice of fertilisers to apply.
Photo: Growth present in a number of the plots in spring 2014, the 6th year of the study at the 'Kia-Ora' site, near Bookham
The alternative fertiliser products trialled included manures, composts, crushed rock, rock phosphate-derived products, concentrated ash and microbial products. Annual measurements were made of soil chemical properties, pasture yield and botanical composition during winter and/or spring as well as the relative effectiveness of products per unit of pasture grown. Soil microbial community structure under each fertiliser treatment was also analysed in the sixth year of the study.
Fertiliser products with substantial quantities of P resulted in significantly higher pasture production and clover content in pastures compared to the unfertilised control treatment. The solubility of the P present in the products also played a key role in the pasture response. Products consisting of a high proportion of plant available P resulted in a quick pasture growth response compared to products containing very slow release forms of P, which showed a delayed pasture growth response. The cost-effectiveness of the products in relation to pasture growth varied considerably and was a function of rate and frequency of application as well as amount and solubility of P applied.
Despite large differences in pasture growth across the various fertiliser treatments, there was no significant effect of the alternative fertiliser treatments on microbial community structure compared with either the superphosphate or unfertilised control treatments. The observed variation in bacterial, fungal and archaeal community structures across all fertiliser treatments was best explained by soil pH or aluminium concentration, which was influenced differentially by the fertiliser products. Fungal community structure was also correlated to pasture productivity parameters, that included pasture yield, clover percent and soil available P.
These findings demonstrate a highly resilient soil microbial community that was influenced minimally by use of the alternative fertiliser products. Soil microbial community analysis as a predictor of the productivity of a pasture system is currently not an informative and defined tool to aid on-farm decision making, and the overall findings of this study support this. It is worth noting, however, that for a small number of soil fungal groups a relationship was found to pasture productivity parameters, indicating that in the future it might be possible to identify specific indicator organisms that can be linked to higher or lower levels of pasture production. Understanding relationships between soil microorganisms and pasture production will none-the-less continue to be a significant challenge, given the complexity of the microbe-soil-plant interface.
The key conclusion of the work undertaken is, farmers should continue to use economic rationales associated with pasture productivity response to guide their decision making around the choice of fertilisers to apply. In doing so, they can be re-assured that they are not having a detrimental effect on the microbial communities that are present in the topsoil.
This research study was hosted and supported by Binalong Landcare, subgroup of Harden-Murrumburrah Landcare with trials conducted on properties owned by Bruce and Noeleen Hazell ‘Kia-Ora’ Bookham, Gary and Hansie Armour ‘Te Kooti’ Bookham and Old Bundemar Pty Ltd (former managers Geoff and Fiona Henderson) ‘Glenroy’. Funding was received from NSW DPI, former NSW
Department of Environment and Heritage, former Murrumbidgee Catchment Management Authority, the Australian Government’s National Landcare Program, Woolworths, NSW Local Land Services, Meat & Livestock Australia (E.PDS.1503 Final Report), Sibelco Australia, and Sheep Connect NSW.
Photo: Spring Field day in Oct 2010 on 'Kia-Ora' trial site, Bookham NSW
Details of the research (Comparative effect of alternative fertilisers on pasture production, soil properties and soil microbial community structure) were recently published in CSIRO journal, Crop and Pasture Science,Volume 70 (12) 2019. Authors were ex NSW DPI Agronomist and now Yass based Local Land Services Senior Agricultural Adviser Fiona Leech, Dr. Alan Richardson CSIRO Agriculture & Food, Dr. Michael Kertesz University of Sydney, Beverley Orchard, formerly NSW DPI, Dr. Samiran Banerjee North Dakota State University, and Phillip Graham, formerly NSW DPI.
If you would like a copy of the journal publication please contact Fiona Leech, South East Local Land Services, Yass (Email: email@example.com; Mobile 0427201805).
You can find out more about the project here.
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