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. This research study was hosted and supported by Binalong Landcare, subgroup of Harden-Murrumburrah Landcare. You can find out more about the project here.
About the trial
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.
Results
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.
Key findings
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.
Further information
Read more about the results of this research here.
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. If you would like a copy of the journal publication please contact Fiona Leech, South East Local Land Services, Yass (fiona.leech@lls.nsw.gov.au or 0427201805).
