Can Biostimulants be used to Support Soil Health?
19 December 2024There is a lot of discussion around managing soils to achieve ‘healthy soil’ status. Soil health indices comprises a mixture physical, chemical and biological parameters. There are many products on the market which promote potential benefits to soil health through the manipulation of the soil biology.
What is soil health?
The Food and Agriculture Organisation defines soil health as:
“the capacity of soil to function as a living system, within ecosystem and land use boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and promote plant and animal health. Healthy soils maintain a diverse community of soil organisms that help to control plant disease, insect and weed pests, form beneficial symbiotic associations with plant roots; recycle essential plant nutrients; improve soil structure with positive repercussions for soil water and nutrient holding capacity, and ultimately improve crop production" (FAO, 2008).
What lives in the soil?
The term ‘soil biology’ refers to all living organisms within the soil. So what lives in soil? The table below demonstrates key organisms, number of different species and their abundance within a metre squared of soil.
Approximately 10% of soil is made up of organisms. So, if you imagine 1 hectare of land this would roughly equate to
1-5 t/ha Fauna
3.5 t/ha Fungi
1.5 t/ha Bacteria
6-10 t/ha or 8.5 – 14
What are biostimulants?
The term 'biostimulant' covers a very wide range of products but the European Biostimulant Industry Council defines them as ‘substances and/or microorganisms whose function when applied to plants or the rhizosphere is to stimulate natural processes to benefit nutrient uptake, nutrient use efficiency tolerance to abiotic stress, and/or crop quality, independently of its nutrient content.’ Generally biostimulants are either:
- Microbial (E.g. Plant growth promoting bacteria and rhizobacteria (PGPR)
- Non-pathogenic fungi Arbuscular mycorrhizal fungi (AMF)
- Protozoa and nematodes
- Non-microbial products (seaweed extracts, humic substances, phosphite and other inorganic salts, chitin and chitosan derivatives, anti-transpirants, protein hydrolysates and free amino-acids, non-essential chemical elements, and complex organic materials)
AHDB Considerations when using biostimulants:
- Some biostimulants are derived from mammalian tissue by-products, including pork and beef material – check that your trade customers or buyers are happy for you to use such materials
- If using a biostimulant containing microorganisms, consider the environment in which they will be used
- Carefully follow product labels for time and rate of application. If necessary, consult a professional agronomist
Take away messages
- There are a range of products available, which can vary in nutritional composition and efficacy in terms of productivity.
- Efficacy of products in field conditions can vary from laboratory-based evidence reported.
- There is limited evidence demonstrating a positive influence of biostimulant applications on the soil biology and soil health, particularly in field conditions.
Sarah Buckingham, SAC Consulting
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