Inoculant

An inoculant is a preparation containing live microorganisms intended to introduce or augment beneficial microbial activity in plants, soils, seeds, or post-harvest substrates. In agriculture, inoculants are used to promote plant growth by fixing atmospheric nitrogen, solubilizing phosphorus, enhancing nutrient uptake, or suppressing pathogens. They may be seed coatings, soil drenches, or mixtures applied to transplants.

Common categories include nitrogen-fixing inoculants for legumes (such as Rhizobium and Bradyrhizobium), phosphate-solubilizing bacteria, and mycorrhizal fungi (vesicular-arbuscular mycorrhiza). Silage inoculants use lactic acid bacteria to control fermentation. Seed inoculants aim to establish beneficial microbes directly with the seed, while soil inoculants target the root zone or soil ecosystem.

Mechanism: beneficial microbes colonize the root zone or tissues, form nodules or networks, fix nitrogen or solubilize nutrients, produce growth hormones, or antagonize pathogens, resulting in improved growth, yield, or stress tolerance.

Production and quality: products are formulated with carriers such as peat, vermiculite, talc, or liquids. Viability is expressed as colony-forming units per gram or per milliliter. Storage typically requires cool, dry conditions to maintain effectiveness.

Limitations and regulation: field performance depends on crop, soil, climate, and compatibility with other inputs. Registered products are subject to quality standards and labeling in many jurisdictions. Inoculants complement good agronomy but do not replace proper nutrient management.