- The use of biological products is becoming more widely accepted by the farming community, but there are numerous questions around whether the products being sold to improve soil health actually change soil biological activity and ultimately are cost effective in maintaining or increasing production
|
- Soil biology remains poorly understood in the context of agricultural farming systems
- Key physical and chemical constraints should be corrected before considering biological products
|
Understanding the question
|
| Why is it important to me as a farmer?
|
- An active soil biota is essential to improve and sustain agricultural production - a healthy soil is one that is full of life where organic material and nutrients are recycled
- Soil biology contributes directly to more profitable and sustainable farming
- High levels of organic matter helps to maintain agricultural production through its positive role in maintaining soil health, raising fertility, reducing erosion and encouraging soil biota
|
- Physical and chemical constraints such as compaction, waterlogging, soil acidity and low soil organic matter content are likely to be your main regulators of soil biological activity
|
| Background on soil biology
|
- Soil biology relates to the organisms within soil that carry out a wide range of processes that are important for soil health and fertility
- These organisms decompose and recycle soil organic matter (SOM), improve nutrient availability and soil structure, transmit or prevent diseases, and degrade pollutants
- The total number of organisms, species diversity and their activity will fluctuate with changes in the soil environment
|
|
- To date, with few exceptions (the most obvious being Rhizobium and some newer fungal inoculants)) there has been little validated scientific evidence published on the benefits of adding microbial inoculums to soil
- There are currently many commercial products on the market that are ill-defined and untested. The lack of information extends not only to the potential benefits associated with the use of these products but also to the best mode of application, length of efficacy and effects of climatic influences (since many of these products are tested overseas or in high rainfall environments)
|
- For many years the physical and chemical aspects of soil have been well researched and defined � what is now apparent is that we need rapid and extensive research on soil biological properties and soil organisms to help determine how soil biology can be managed to increase the productivity of a soil
- The lack of clear evidence not only extends to microbial inoculums but also to products designed to stimulate the biota already have in soil (for example through the application of organic �food�). There is no doubt that increasing our knowledge of soil biology could provide enormous potential for improving soil health and function, but also provides the opportunity for commercial gain
|
Managing the soil biology with products
|
Consider the following:
- There is very little, if any, biological activity in dry soils � consider the survival potential of any applied organisms or how a stubble breakdown product might work when the soil is dry
- There are billions of soil organisms not yet identified (many are very hard to distinguish and identify) that perform important soil functions (that are more-readily measured) � consider investing in understanding your soil and how it functions
- There are things you can already do to support the development of �good� biology (i.e. zero tillage, stubble retention) � start with the basics at low cost
- The potential beneficial effects of soil biology though important can be limited by other soil constraints such as compaction and soil acidity � target amelioration of the most important significant constraints first � you will be supporting the development of �good� biology at the same time
- Ask yourself what it is the soil biology product is delivering that is unique, will it work in your environment (i.e. ask for local validated data or if not available for a free sample to be included in a replicated test strip trial), and most importantly is it addressing your most constraining problem?
What about applying microbial products to the soil?
Source: Schwenke, 2004
- Commercially available microbial products claim not to increase this soil fraction directly, but rather to inoculate the soil organic matter (SOM) with specific organisms or groups of organisms that will rapidly build up in the soil to a point where they will influence soil properties
|
- Favourable environmental conditions of moisture, aeration, temperature, pH, and energy source are required for inoculants to build up in soil; conditions under which native soil biota are also likely to be abundant and strongly competitive against the added organisms
- Until more widespread scientific testing of such products in the field is conducted, farmers should be equipped with robust methods of making their own comparisons between current and new technologies, rather than the ad hoc testing that predominates
What about applying humic acids to the soil?
Source: Schwenke, 2004
- Humic acid or humate products are generally extracts from leonardite or lignite, a mineral similar to brown coal
- As with microbial products, increasing SOM measurably with humic acid products is unlikely given the scale of addition advocated versus the background levels in SOM
- However, there are many claims and some reports in the scientific literature that adding humic acid products to soils may stimulate plant growth and increase yield, possibly due to mechanisms such as delaying precipitation of phosphorus from mineral fertilisers in certain soil types
- Whether such applications will work and, if so, are economical, will be affected by your particular farming system with its unique combination of soil type, climate, landscape, paddock history and economic situation. Determining this requires unbiased, scientifically rigorous, but not necessarily complex, testing and evaluation
|
| What is the best practice?
|
- Before investing in any biological products, it is suggested that farmers should undertake a soil health assessment to identify key constraints to production
- Experience suggests that physical and chemical constraints such as compaction, waterlogging, soil acidity and low soil organic matter content are likely to be your main regulators of soil biological activity
Questions to ask about soil biology products
- When contemplating using these products, use caution and ask questions
- If you want to continue along the soil biology product route, undertaken your own trials using in-paddock strips ir paired trial techniques prior to extending the practice to your whole farm. However, be aware that it is anticipated that you will need to undertake the trials for a minimum of 3 years to recognise any improvement in production and soil health
|
- Identify what is wrong with your soil first
- Is the product registered?
- Registration requires sufficient scientific data
- Products certified for organic use are not necessarily certified with APVMA
- Does the label carry key information?
- Is the product suitable?
- Some products may only be effective in certain soils, climates or plant type
- Will the product be a long-term solution?
- Many products promise a quick fix to a recurring problem
- Changes in management practice are more reliable means of improvement
- Is the product part of a management package?
- Is it the changes in management practice or the actual product that leads to the improvement in soil health?
- How can I tell if the product really works?
- Request detailed trial results for your area
- Can I mix products?
- Can I talk to other users?
- Request contact with Australian farmers who have tried the product in your region
- How can I find out more?
|
Other related questions in the Brown Book
|
|
Brown Book content has been based on published information listed in the References section below
|
- Johnston, T.Understanding Soil Biology. � DPI Healthy Soils Modules. DPI Victoria.
- Clarkson T, Department of Primary Industries on behalf of the Corangamite Catchment Management Authority (2007) - Corangamite Soil Health Strategy 2007. Corangamite Catchment Management Authority, Colac, Victoria.
- Soil Biology - Victorian Resources Online � Department of Primary Industries, Victoria.
- Why Soil Organic Matter matters. CSIRO.
- How Much Carbon can Soil Store. Soilquality.org.au
|
- Using biological activity to improve soil. Section D7 - SOILpak - southern dryland farmers. Department of Primary Industries, NSW.
- Soil carbon. Department of Primary Industries, NSW.
- Woady Yaloak Catchment Group. Evaluating alternative fertilisers and biological products for pastures and crops. Result of the 2009 and 2010 seasons.
- Kirkegaard J, Kirkby C, Gupta V. Management practices for building soil carbon. CSIRO.
- Schwenke, G. (2004) Soil organic matter, biological activity, and productivity: myths and realities. Soil Biology in Agriculture Conference Proceeding 2004. NSW Department of Primary Industries, Tamworth.
|
|
