How should biostimulants be used?

Biostimulants require careful management before, during and after application.

Environmental conditions can influence the degree to which a crop responds to a biostimulant.

External factors that potentially impact biostimulant performance include:

• Product usage, including timing and rate
• Soil physical, chemical and biological characteristics
• Weather, such as temperature and rainfall
• Crop type, variety and growth stage
• Presence of other plants
• Other management factors

As microbial biostimulants are living organisms, they require particular care.

Management requirements vary depending on the organism used but there are general guidelines.

Product selection: When selecting a product, always check the claims and the supporting evidence that backs them up. Also, consider the application method. For example, seed coatings may provide better access to plant roots during early growth stages. Consider testing the product across a small area first to see how it compares with your standard approach.

Product application and storage: Follow the manufacturer’s guidelines, which will include information on application timing and rate. Some products have a relatively short shelf life, especially if they contain living organisms or other biologically active components. The manufacturer will indicate if any specific storage conditions, such as temperature and humidity requirements, are critical to maintain the product’s efficacy.

Product compatibility: Some products may be incompatible with other products. The manufacturer may cite specific requirements. This could include whether products can be tank-mixed or if they are likely to interact with other products. For example, a fungal inoculant may be adversely affected by some fungicides. There may also be an optimum pH for tank-mix water.

Soil physical characteristics: Adverse conditions may reduce product effectiveness. Consider how soil physical properties, such as clay content, soil water potential and soil temperature, could influence product performance.

Soil chemical characteristics: In unsuitable soil chemical environments, the inoculant may not be effective. If unknown, conduct soil sampling and analyses – for example, to determine soil pH.

Soil biological characteristics: Follow manufacturer’s guidelines to minimise risk of competition from the local microbial community.

Crop type and variety: Biostimulant performance can vary widely across crop species. It is important to understand the requirements of the organisms in biostimulants. For example, oilseed rape does not form associations with mycorrhizal fungi. There is even evidence that the efficacy of biostimulants, including non-microbial products, differs across varieties.