Timing, one the keys to maximise results when using biostimulants

By Josué Castellanos, R&D specialist;   Marcos Alajarín, R&D Specialist;  Dr. Cathal Daynes, Global Technical Manager at Tradecorp

As all growers know, weather conditions change across the season and this affects crop growth. In fact, each year crops grow and develop in a constant interaction with the local weather and environmental conditions. The final yield and quality of harvest therefore are the result of how well the crop could deal with, and respond to, these environmental and weather conditions.

Crops do not alter their “normal” growth trajectory during small changes in environmental conditions. However, if these changes are large enough that they require the crop to alter their “normal” growth and metabolism, we speak about the crop suffering from abiotic stress (Brown & Saa, 2015).

The application of biostimulants can enhance crop yield and quality by improving their tolerance to abiotic stress. In recent years, the use of biostimulants has been recognised as a good agricultural practice, which may assist in making agriculture more sustainable and even more environmentally friendly.

What is a biostimulant?

A “biostimulant” in agriculture, according to the definition in the upcoming European Union fertiliser regulations, is a product that stimulates plant nutrition and growth processes independently of the product’s nutritional content. Biostimulation has the sole aim of improving one or more of the following characteristics of the plant or the plant rhizosphere (root zone):

   •nutrient use efficiency; 

   •tolerance to abiotic stress;

   •quality traits;

   •availability of confined nutrients in soil or rhizosphere

Biostimulation has been demonstrated to effectively reduce the impact of abiotic stress on crops when applied appropriately helping to achieve the crops full potential. An important point about biostimulants is that they have no specific effect on pathogens or pests and to control these biotic challenges plant protection products are still needed.

How do biostimulants work?

Biostimulants have the capability to trigger the natural response functions of crops to combat abiotic stress. In essence, with or without biostimulants, the crop will alter its metabolism to respond to abiotic stress. However, the use of biostimulants on crops allows for a quicker, more effective and /or more efficient response. 

There are a variety of biostimulants, and they differ in their origin and / or their mode of action within the plant. In general, biostimulants can be allocated to one of seven groups: Humic / Fulvic Acids, protein hydrolysates (e.g. Amino Acids), seaweed extracts, chitosan, inorganic compounds, beneficial fungi and beneficial bacteria (du Jardin 2015).

Knowledge about the mode of action of each biostimulant will enable growers to make the best decision about what biostimulant to apply, when and what dose to use. The growers will also know what beneficial effect that is expected from that particular biostimulant application (Brown & Saa 2015), and this will benefit the grower’s decision making.

What application timing is best when using biostimulants?

Preventive biostimulant application - Use before the stress occurs

Some biostimulants prepare or prime the response of the crop to enable it to better resist abiotic stress before the actual stress occurs. These biostimulants generate a cascade of signals that "put the crop on alert". 

When a passing or temporary stress occurs, for example some hot, cold or cloudy days, the alert previously generated by the preventive biostimulant application allows the crop to respond quickly and effectively to the abiotic stress event. This allows the crop to maintain or minimise disruption to productive growth and metabolism.

Primactive effect - Preventive biostimulants

One type of preventive alert effect is the unique “Primactive” effect of Tradecorp’s Phylgreen range of products that are based on Ascophyllum nodosum seaweed extract. Preventive biostimulation, such as those with Primactive effect, can help during mild stresses or the early stages of more severe abiotic stress events. Preventive Biostimulants can be viewed as the growers first line defence option that allow crops to minimise or delay the disruption to normal growth.

Recovery Biostimulant application - Use during or after the stress has occurred

During more severe or prolonged abiotic stress situations, such as a long heatwave or cold spell, the crops demand for resources will alter away from yield and quality production to focus on more essential basic growth and survival functions. This consequently reduces final harvest potential.

In these situations, the application of corrective, post-stress or recovery Biostimulants will benefit the crop, and also the grower’s profitability. Recovery Biostimulants help the crop to return to normal growth as quickly and efficiently as possible, thus recovering some, but not all of the potentially lost yield and quality. In these recovery situations, solutions such as Tradecorp’s Amino Acid range are the go-to Biostimulants of choice.

Amino Acids as recovery biostimulants

Nature consists of the basic elements, such as Oxygen, Hydrogen and Carbon, that combine to make all matter that is present in the world. A similar principle operates in living organisms, like plants, which are composed of the “elements of life”, the twenty or so foundation or elemental Amino Acids.

These Amino Acids are essential for growth, yield and quality. In addition, they are also key to help crops recover quickly from abiotic stress and resume their normal growth trajectory. Application of recovery Biostimulants such as Amino Acids is thus in perfect harmony with the natural growth and recovery cycle of crops.

As knowledge about Biostimulants and their preventive and recovery modes of action has improved, it has become clear that, similar to pest and pathogen management strategies, a combined abiotic stress management program that integrates both a preventive, and recovery strategy gives the optimum result in terms of yield and quality.

Biostimulants for specific growth stages of the crop

From the above it can be understood that certain Biostimulants have very specific roles in helping prevent and recover crops from environmental and weather stresses. A different source of stress in crops is the stress that occurs each time the crop passes through a growth stage, for example changing from the germination stage to the vegetative stage, changing from the vegetative stage to the flowering stage, etc.

Similar to preventive and recovery Biostimulants, there are specific Biostimulants that target, and help to reduce, each of these specific crop growth stresses.

Humic and fulvic acids for root growth 

Humic and Fulvic Acids help in the recovery of the degraded structure of soils, in the retention and availability of nutrients in soil, and facilitate improved soil moisture retention, among other functions. Humic and Fulvic Acids, such as Humistar / Humifirst, have also been shown to have a direct Biostimulation effect on crops, in particular by triggering increased root growth that facilitates improved overall crop performance (Szczepanek & Wilczewski 2011). This Biostimulation effect is particularly beneficial in the early stages of growth, when more root development is desired, such as during the germination phase, during transplant, during vegetative growth phases and at the breaking of root dormancy in perennial crops.

Biostimulants can also be incorporated into formulations that contain specific nutrients, such as the incorporation of Humic and Fulvic Acids with the Phosphorus, Nitrogen and micronutrients needed for early and vigorous crop development, as in Tradecorp’s Turbo Root. In this example the synergy between Biostimulants and specific crop nutrition reduces transplant shock and promotes vigorous early growth demonstrating how knowledge of both biostimulants and crop nutrition, when appropriately combined, bring maximum benefit to crops.

Another risk factor during the early phases of crop growth is excess vegetative growth, which can reduce root development. This is a particular risk where basal doses of Nitrogen have been applied to the soil. Specific Biostimulant products that promote balanced root and shoot development have an important role during this growth period, for example Ruter AA. In this product, the key for this balanced root and shoot development is the combination of amino acids with nutrients favouring balanced early growth, such as Phosphorus and Potassium, as well as Molybdenum to enhance the plant metabolism of the applied basal Nitrogen fertiliser. 

Biostimulants for enhanced flowering / fruit set

As crops change from vegetative growth to flowering and then fruit set, a large biophysical and biochemical change is produced, and stress is triggered, in the crop. During these phases of growth, specific targeted Biostimulants can have a very strong effect on flower number, fertility and fruit set.

Targeted biostimulants to benefit crop growth during these critical growth phases often have a seaweed or amino acid base, as both of these biostimulant classes have beneficial effects on either flower number, pollen vitality or pollination success. From a nutritional standpoint, Boron and Molybdenum are key nutrients demanded by the crop at this growth stage. Therefore, it is logical to develop a product that combines one of the biostimulant raw materials with Boron and / or Molybdenum to produce a combination biostimulant / nutritional product, for example Florastart or Phylgreen B-Mo. 

By taking this approach, it is easier for growers to ensure they are giving optimal nutritional and biostimulation to their crop at this key growth stage using a single product. This avoids the need or confusion of having to mix and apply multiple different biostimulant and nutritional products that costs the grower time and increases the risk of an adverse tankmix. 

This scenario is a good example of the development of the biostimulant market overall. Whereas in the early days of biostimulant use it was more common to apply a pure biostimulant and then mix it with other nutritional products, it is now usual to apply a single premixed product that contains both. 

Biostimulants and better fruit fill

During fruit fill the diversion of energy to fill the fruit and produce viable seeds results in increased internal crop stress.

Biostimulant with yet different modes of action are often beneficial during this stage, such as biostimulants that enhance the transport of sugars, like Amifol K, or solutions that promote fruit fill and quality thanks to added Calcium, like Phylgreen Electra. 

Other options, promote fruit fill, while containing biostimulants that focus on reducing the negative effect of adverse temperature and reducing the effect of free radicals (also known as Reactive Oxygen Species - ROS). Free radicals have many negative effects on crops such as reducing amino acid and thus protein content.

What next for biostimulants?

In little under a decade, the use of biostimulants has grown from almost zero to become a multi-billion dollar industry. Knowledge about the use and function of biostimulants has also increased at an exponential rate. 

First came the knowledge about which products had biostimulant effects, then came increasing knowledge about the mode of action and how biostimulants work inside the crop. This has enabled increasingly precise recommendations regarding timing and dosage of biostimulant applications and has led to more consistent results and greater returns on investment for growers.

The use of biostimulants in agronomic programs continues to expand globally as this new knowledge is applied. At the same time, a new generation of biostimulants are currently under development, harnessing the knowledge gained during the past decade and including new sources of raw materials, such as secondary metabolites of bacterial fermentation. 

As a result, the use of biostimulants will continue to expand in this new decade gaining an increasing importance in assisting agriculture be more sustainable while at the same time helping to increase yield and quality to feed the growing global population.

This article was originally published in AgroPages' 2020 Biologicals Special. 

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