Aug 23, 2021

Biostimulants and Crop Responses

Biostimulants and Crop Response: What the Research Shows

Modern agriculture operates in a world of constant change. Market fluctuations, evolving production systems, and increasingly variable climate conditions mean that what worked last season may not be enough for the next. For growers navigating these challenges, improving the efficiency and resilience of their cropping systems has become a top priority.

One category of products receiving increasing attention in both conventional and organic agriculture is plant biostimulants.

Plant biostimulants are substances or microorganisms applied to plants or soils that stimulate natural biological processes, enhancing nutrient use efficiency, tolerance to abiotic stress, crop quality, or nutrient availability—independent of the product’s nutrient content (Du Jardin, 2015; Rouphael & Colla, 2020).

Rather than supplying nutrients directly, biostimulants work by supporting plant physiology and the surrounding soil biology, helping crops use available resources more effectively.

Common benefits associated with biostimulant use include:

improved nutrient uptake and nutrient use efficiency
enhanced root development
improved tolerance to environmental stresses such as drought, salinity, or heat
improved crop quality and yield stability

These effects can help growers maintain productivity even under challenging conditions.

Major Categories of Biostimulants

Biostimulants encompass a diverse group of materials that influence plant growth through biological or biochemical mechanisms. Some of the most widely used categories include:

Microbial Biostimulants

Beneficial microorganisms such as Bacillus, Paenibacillus, Pseudomonas, and mycorrhizal fungi are widely used as microbial inoculants. These organisms can improve plant performance through mechanisms such as nutrient solubilization, hormone signaling, and improved root system architecture.

Seaweed and Plant Extracts

Extracts derived from seaweeds such as Ascophyllum nodosum have been used in agriculture for decades. These materials contain complex mixtures of bioactive compounds that influence plant metabolism, including polysaccharides, phytohormone-like compounds, and antioxidants.

Humic and Fulvic Substances

Humic substances are naturally occurring organic molecules formed during the decomposition of plant and microbial material. These compounds can influence nutrient availability, root development, and soil structure.

Protein Hydrolysates and Amino Acids

Derived from plant or animal proteins, these materials supply bioactive peptides and amino acids that can influence plant metabolic processes and stress tolerance.

Biopolymers and Functional Compounds

Certain natural polymers, such as chitosan, function as signaling molecules that stimulate plant defense pathways and stress responses.

What the Research Shows

Scientific interest in biostimulants has increased dramatically over the past two decades. Hundreds of peer-reviewed studies have explored how these products influence plant physiology, soil biology, and crop performance.

A comprehensive review by Calvo et al. (2014) highlighted growing evidence that biostimulants can improve root growth, nutrient uptake, and tolerance to environmental stress. Subsequent work by Halpern et al. (2015) further demonstrated that biostimulants can enhance plant productivity and may allow for reductions in conventional fertilizer inputs in some cropping systems.

More recent research has expanded our understanding of the mechanisms behind these effects. Studies have shown that biostimulants can influence plant hormonal signaling, antioxidant activity, and root system development, helping plants maintain growth under conditions such as drought, salinity, and temperature stress (Rouphael & Colla, 2020; Bulgari et al., 2019).

Microbial biostimulants, in particular, have attracted attention for their role in improving nutrient use efficiency and rhizosphere function. Beneficial rhizobacteria can enhance nitrogen fixation, phosphorus solubilization, and root development, contributing to more efficient nutrient acquisition by crops (Backer et al., 2018).

Evaluating Biostimulants on Your Farm

While scientific research supports the potential benefits of biostimulants, field performance can vary depending on soil type, climate, crop species, and management practices.

For this reason, many agronomists recommend conducting on-farm trials when evaluating new products. Replicated strip trials allow growers to compare treated and untreated areas within the same field conditions, providing valuable insight into how a product performs within their specific production system.

In addition to yield and crop quality, growers often monitor indicators of soil health, including soil structure, organic matter, microbial activity, and water infiltration.

Biostimulants as Part of a Broader Soil Health Strategy

Biostimulants are most effective when integrated into a broader management strategy that supports soil health and plant resilience.

Practices such as crop rotation, reduced tillage, and organic matter management help maintain the biological and physical structure of soils that plants depend on. These systems create an environment where microbial biostimulants and other biological inputs can function most effectively.

When used thoughtfully alongside sound agronomic practices, biostimulants can help growers build cropping systems that are more efficient, resilient, and productive over time.