Q: What are biologicals and how do they work?
A: Have you ever thought about the link between biologicals and soil health? If your answer is yes, you are not alone. This article will attempt to clear up some confusion around biologicals and how they improve soil health, with some insights on when and where they perform optimally.
Let’s start by defining biologicals. Biologicals are products derived from naturally occurring micro-organisms, plant extracts, beneficial insects, or other organic compounds. Biologicals can be grouped into three categories: biofertilizers, biostimulants and biocontrols.
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Biofertilizers improve plant nutrition and include symbiotic and free-living microbes that can produce plant-available nitrogen as well as solubilizers of phosphorus and potassium. Other examples include arbuscular mycorrhizal fungi that can explore more nutrients beyond rooting areas and biocatalysts that contain metabolites produced by microbes in recycling nutrients.
Biostimulants include microbials that produce or alter plant hormones to stimulate growth, nutrient uptake or relieve abiotic stress. Other examples include amino acids or protein hydrolysates, which provide available nitrogen and stimulate microbial activity; humic and fulvic acids, which provide a food source for microbes and improve soil structure; and seaweed and plant extracts with an antioxidant effect to relieve stress and promote microbial activity.
Biocontrols are utilized in the management of pests and diseases, and they include biochemicals such as pheromones, plant extracts and organic acids. Microbials and insects or parasitoids are also used as biocontrol agents.
In Canada, biofertilizer and biostimulants are regulated as supplements under the Federal Fertilizer Act and Regulation, while biocontrols are regulated as biological control agents under the Federal Plant Protection Act and Regulation.
Both are administered and enforced by the Canadian Food Inspection Agency.
Soil health can be defined as the continuous capacity of a soil to function as a vital living ecosystem that sustains plants, animals and humans. At the heart of soil health is the connection of soil’s physical, biological and chemical properties or indicators.
Important physical properties include texture, bulk density, water-stable aggregates and water holding capacity. Chemical properties include pH, electrical conductivity, nutrients, cation exchange capacity and base saturation. Biological properties include organic carbon, microbial biomass and carbon and nitrogen mineralization. Therefore, a healthy soil should have an overlap of these physical properties, which affect water availability; chemical properties, which affect nutrient availability; and biological properties, which affect nutrient recycling.
As mentioned earlier, biologicals enhance microbial and biochemical activity in the soil to influence the biological domain of soil health and, together with their role in improving plant health, are expected to increase crop yield. However, there are times when biologicals may not be as effective as expected.
Key environmental factors and soil properties that have been shown to affect biological effectiveness include climate, soil pH, organic matter, salinity and soil-available macronutrients.
For example, biofertilizer and biologicals increase yield in a dry climate and at moderate acidity and alkalinity but may reduce yield in soils with high organic matter. Biostimulants also increase yield in saline soil and in soils with low available phosphorus and potassium. Overall, biologicals tend to be more effective in marginal soils and under stressful conditions. When talking about crop types, vegetables and pulse crops have been shown to have a high response to biologicals while cereals generally have a moderate response.
By improving soil health, including the use of biologicals that enhance microbial and biochemical activities in the soil, growers can improve the productivity of their operations. Emerging soil heath techniques such as metabolomics and metaproteomics will continue to enhance our understanding of how biologicals contribute to soil and plant health.
– Sola Ajiboye, PhD, PAg, MBA, is a manager of agronomic solutions with Nutrien Ag Solutions in the southern Alberta division.
