Agronomy Crop Inputs The 411 on Biostimulants

The 411 on Biostimulants

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As biostimulants have grown in popularity with many options available, you may be wondering what these products are and if they’re right for your farm.

Biostimulants represent a rapidly growing area of interest for boosting many aspects of crop production, but researchers are urging caution for evaluating the value of these innovative products.

“A wide variety of biostimulants are being developed to enhance nutrient uptake or availability through boosting root growth, solubilizing certain nutrients, and/or stimulating growth of soil microorganisms,” says Alan Blaylock, senior agronomist at Nutrien.

“There are dozens if not hundreds of products on the market, but in many cases, their active ingredients and the modes of action of those ingredients are not well known. Some may affect crop gene expression or elicit stress tolerance or stimulate the plant in some other way, but often little is known about why the response is occurring.”

Biostimulants are substances or microorganisms whose function, when applied to plants or the rhizosphere (soil zone directly surrounding the roots), is to stimulate natural processes to benefit nutrient uptake, nutrient use efficiency, tolerance to abiotic stress and/or crop quality, according to Nutrien. They include amino acids, sugars, alcohols, fermentation metabolites, organic acids (humic, fulvic), seaweed/kelp extract, hormones and enzymes. They can be divided into two categories — synthetic such as inorganic salts and natural like algal extracts.

In potatoes, Tommy Roach, vice-president of product development and technical services at Nachurs Alpine Solutions, explains humic acids have long been used to help improve phosphorus uptake, “especially in light of the fact that a potato plant is very inefficient in acquisition and uptake of this nutrient.”

He adds that foliar-applied biostimulants are gaining popularity in potatoes, but their effectiveness on yield and tuber quality has not yet been determined. While biostimulants can generally increase root growth, improve stress tolerance and promote greater photosynthetic capacity, Roach says increases in yield are typically offset by a reduction in tuber quality.

Biostimulant Product Development

In the development of biostimulants, Yara Biostimulants Product Manager Antonis Angeletakis says it’s very important for a company’s research and development team to first define when, how and why the product is going to be used.

“In potato, we can have products for seed treatment, foliar or soil applications that will be targeting specific phenological stages of the crop,” Angeletakis says. “For example, a seed treatment formulation can enhance seed germination and plant vigour and viability during the initial crop cycle when plants are more sensitive to adverse environmental conditions. Also, the stages of tuber initiation and early tuber bulking are critical stages in order to improve plant productivity and quality of the produce and enhance tolerance to abiotic stress.”

The product development and commercialization process can take anywhere from three to five years. It starts with the selection of high-quality raw materials, then the development of a formulation based on different bioactive components and nutrients to address specific crop responses, Angeletakis explains. Different formulation prototypes will be developed and tested for quality and long-term stability.

The next step is then to understand the effect of the prototypes on the crops and identify the optimum range of rates and application timings for each crop in the field in different regions, in terms of efficacy and crop safety factors.

Research Round-Up

In 2019, a group of scientists in Poland and Czechia published an evaluation of how biostimulants affected the health status of potatoes with coloured flesh at harvest and after five months of storage. One of the biostimulants used was a mixture of salts, two contained an extract of brown algae with other compounds, and the other an isolate of fungal spores.

The researchers found all four of these biostimulants decreased the occurrence frequency of the pathogens responsible for dry rot and black scurf after harvest. They also found higher concentrations of chlorogenic acid (a substance which may help lower blood sugar levels and reduce insulin spikes) in response to application of the biostimulants with salts and the fungal spore isolate.

In 2019, Carl Rosen, professor and head of the Department of Soil, Water, and Climate at the University of Minnesota, along with colleagues there and at the United States Department of Agriculture-Agricultural Research Service, published a study on biostimulants in potatoes. They found potatoes containing an amino acid blend (AAB) with and without nitrogen-fixing microbes (NFM) produced modest improvements in tuber yield, under limited conditions, compared to urea alone.

“Effects on yield were generally positive but inconsistent,” says Rosen. “For example, in the first year, yield increased with NFM and AAB at the low N rate but there was no effect at the high N rate. In the second year, biostimulants had no effect on yield at the low N rate but increased yield over urea alone at the high N rate. We suggest that more field research is needed to identify conditions (soil, climate, fertilizer, cropping system etc.) where biostimulant applications may be beneficial.”

Looking Forward

There are numerous biostimulants now on the market but Rosen says it’s difficult to evaluate the effectiveness of all the products available. Studies of them need to be based on replicated field studies over multiple years.

“Based on our research, there may be a slight yield increase some years, but there are no silver bullets,” he says. “All biostimulants come with a cost. This increase in cost has to be covered by either an increase in yield or a decrease in inputs, usually N. Based on the literature, you will not find many field-scale studies published, and those that are published usually report inconsistent results. The most positive results with biostimulants are usually based on greenhouse experiments, but these results do not often translate to the field.”

Rosen and his colleagues stress that field trials with biostimulants should not only assess yield but also show how the nutrients in the environment fare, particularly nitrogen. He believes biostimulants research should involve fertilizer rates, especially for nitrogen and phosphate, which are lower than recommended to determine if biostimulants can reduce fertilizer inputs, increase fertilizer use efficiency and reduce nutrient losses.

Blaylock thinks growers need to be cautious with biostimulants until more research is done. He suggests on-farm experiments are a good way for growers to test a product as the trials will involve each grower’s chosen varieties and growing conditions. He also advises the most informative and reliable trials use paired strips with and without the product of interest replicated in different areas of a field, rather than comparing one field with another.