Growers need to be clear about what they want from their biostimulants, says Dr Simon Fox of Emerald Research. They can perform several supporting functions to the crop by stimulating or enhancing the crop’s natural processes that, together, increase efficient nutrient usage, improve plant growth and environmental tolerance.
Simon says: “Seaweed, humic acids, amino acids and other biostimulant products are some of the important tools in the grower’s armoury as they can help improve crop quality and yields, while reducing input costs and minimising the use of pesticides.”
Different biostimulants have activity in different areas, he explains, noting that they can improve everything from germination through rooting structure to vegetative growth, flowering and fruiting, but there is a specific one for each stage. They can also be used tactically to help ameliorate abiotic stress from weather conditions, or to improve photosynthetic ability.
“In the field, when used as a foliar spray, these products can start to work within minutes. The speed with which they take effect depends on whether the formulation is right, because not only does the biostimulant need to be delivered to the crop, it needs to be absorbed and translocated.” Because of the speed at which they become active, their use needs to be appropriate, and Simon emphasises that, for example, a photosynthetic enhancer should be used when weather is dull overcast, and cool, but not in a hot, sunny period.
Other biostimulants are applied on the soil, with the seed or as a seed dressing, focusing on rapid germination, vigour and establishment. “Ideally, there should be a planned programme which will help across the different stages of crop development, such as tuber set and tuber initiation in potatoes.”
Biostimulant effects on planted seed can induce significant benefits, such as emergence as much as seven days earlier, and extra vigour. “Better rooting ensures the plant has more access to nutrients.” As an example, he reports that trials on c/v Innovator planted with a specialised beneficial microbial mixture have resulted in more vigorous plants, particularly when this is followed with a programme of foliar nutrition and biostimulants.
“What is interesting is that the crops that do not receive the biostimulant do not catch up. Decisions may be taken around the market you are supplying; while some growers will be looking for increased tuber numbers, others will seek a larger tuber size.” In crops such as carrots, brassicas or sugar beet, stress can cause bolting. Incidence can be reduced by a biostimulant that makes them more ‘serene’ and delay early onset senescence as the plant tries to set seed, he reports.
“Plants undergo a number of physiological changes to cope with biotic and abiotic stress, and their survival depends on adaptation to a varying environment.” This happens through signalling networks which establish connections between the environmental signals and cell responses.
“Application of the appropriate biostimulant stops the cascade of chemical reactions by suppressing reactions in jasmonic and salicylic acid pathways, for example.
“To then keep the plant in good condition, it should receive a top-up of foliar N, manganese and a stress suppressing biostimulant.” He recommends a holistic approach to biostimulant use, which is programmed for each growth stage of the crop. [see diagram]
“In potatoes, once the canopy is developed, the opportunity to continue broadcast applications with optimum take-up is limited. Foliar applied nitrogen, phosphate, potash, micronutrients and biostimulants can be considered the key to more efficient input usage.” When used with other nutritional supplements, applications made at tuber initiation in potatoes help increase the number of viable sets and extend the life of the green canopy, particularly at bulking, he adds.
“The bigger the canopy area, the more energy is created through photosynthesis, which leads to increased tuber and root size. By ensuring plants remain healthy and can effectively continue their growing cycle, the crop has the best chance of meeting its genetic potential.
“Biostimulant and foliar nutrient programmes can also significantly reduce the need for overall fertiliser inputs and while the decision to apply less nitrogen may be driven by cost and supply as much as for the good of the environment, in the long run, it is where UK agriculture needs to move to.”
Biostimulants – understanding the benefits and what they imply
Choosing from the wide range available of biostimulants can be difficult. Dr Aoife Dillon Principal Scientist Crop Protection at Fera Science Ltd, and formerly technical director at Plant Health Care, talks about the industry and the need for robust data to help drive better informed decisions with no surprises.
Given the rise in fertiliser prices, the potential for biostimulants to enhance nitrogen use efficiency has been brought under the spotlight for many growers, and the team at Fera Science Ltd are working with various partners in the supply chain to understand how biostimulants can help their growers reduce greenhouse gas emissions linked to fertiliser use.
Aoife says: “One of the problems with how we have been using fertiliser to date is that, in many cases, only 60 percent of the fertiliser is taken up by the plant; this not only has economic impacts for the growers, but also implications for the environment. Biostimulants can be used to improve the processes in the soil or the plant; including to stimulate the plant and/or soil for better nutrient use efficiency.”
Some biostimulants can help the plants use the nutrients (including nitrogen) in the soil more effectively, she says. “This effectively opens possibilities of reducing fertiliser use to around 75 percent of the label rate.”
The mechanism behind how this is achieved can be as simple as promoting more vigorous root development, so the plant is better able to access water and nutrients in the soil. R mechanisms can be more complex, for example, through stimulating enzymes related to N assimilation pathways such as nitrate reductase (NR), glutamate synthase (GOGAT), and glutamine synthetase (GS.)
Calcium deficiency can be a threat to tuber quality when they are grown in sandy soils. This is because it can result in internal browning and hollow tubers, and Aoife points out that correcting calcium (Ca) deficiency can be difficult because it is difficult to mobilise in the plant. However, by using the correct biostimulant, it may be possible to stimulate the Ca channels, which can help to reduce incidence of such defects.
“Different biostimulants can be used to improve crop quality attributes; for example, better skins in potatoes, or tolerance to abiotic stress, such as heat, cold or salinity.”
Where there are specific claims, she recommends careful assessment of the volume of data behind the sales literature, as not all biostimulants will deliver the same benefits in all crops.
“Demonstrating efficacy in the field can be difficult, particularly if you are looking at improving tolerance to abiotic stress, as the stress may not materialise that year. When growers use biostimulants to manage abiotic stress they often consider it as an insurance policy. Nitrogen use efficiency is easier to quantify, because it is reflected in yield, and as a rule you know the expected yield.
“It is always important to speak to your agronomist to understand what the benefits imply, and whether more than one trial has been carried out. The question to ask your agronomist or distributor is ‘how does it work’, she emphasises.
Growth of biostimulant sector and regulatory framework
One of the challenges has been the lack of robust science in the sector, which is not surprising as, until recently, there was not even a clear definition of a biostimulant.
“However, we are now moving forward and working towards global harmonise standards; this is important because if there are different standards in different countries, smaller companies lose out, as the cost of registration acts as a barrier to entry.”
Global standards (via ISO Standards) are being established in consultation with biostimulant manufactures from the European Biostimulants Industry Council, members of the scientific research community, and testing bodies, including Fera Science Ltd. This will ensure that biostimulants can only be certified (CE mark) where manufacturers have provided sufficient data to demonstrate that the products are safe and efficacy claims (tolerance to abiotic stress, better nutrient use efficiency etc) are support by sufficient, scientifically robust, data.
“We want to establish standards which are data driven.”