Finding the best way to feed a population that continues to grow is the burning question of our era, says Prof Stephen Rossall. CPM asks him for his view on the role of biostimulants now and in the future.
We’re only just beginning to understand the potential of these exciting incremental technologies.
By Lucy de la Pasture
It’s no exaggeration to say the question of global food security is one of the defining issues of our time. With a world population expected to grow by up to 50% by 2050, driving significant improvements in crop yields isn’t just important – many would say it’s essential and Prof Stephen Rossall is one of them.
“As demand on growers and their crops becomes ever more fierce, agricultural productivity is under threat from a variety of factors, many associated with changing weather patterns. Following the loss of several key crop protection tools due to withdrawal of registration or resistance issues, there’s even more emphasis on establishing healthy, vigorous crops, capable of withstanding pest and disease attack and grow under adverse conditions,” he believes.
In order to meet these challenges, Stephen suggests that it’s a good time to consider an alternative approach to growing crops.
“In recent years, several key studies have proven that improvements in root architecture could have a profound effect in terms of boosting crop productivity and efficiency. While it’s no secret that strong, healthy roots help ensure plants reach their full potential, it does raise an obvious question – with limited access to effective agrochemicals, what is the best way for farmers to strengthen and grow their roots?”
In his research at University of Nottingham, Stephen has been leading the work into the effect of biostimulants on root architecture and growth. Much of his work has looked at phosphites, which are a reduced form of phosphates.
“Used in the right way, biostimulants help optimise the metabolic efficiency of plants and aid resilience to abiotic stress (detrimental effects caused by non-living factors including temperature, light and moisture), so improving yield, quality and overall plant health.
“Biostimulants are still relatively new on the scene and we’re only just beginning to understand the potential of these exciting incremental technologies,” he says.
Despite their proven value, Stephen says biostimulants are experiencing teething problems in the UK and EU markets as governing bodies struggle to get to grips with them. With the law as it stands, products need to be either fertilisers or pesticides in order to be registered.
“Unfortunately, there’s a lack of robust data which is essential in proving to farmers and growers that biostimulants really work and can generate significant economic return. To give phosphites a helping hand, it’s first important to separate the facts from the myths,” he comments.
“Firstly they’re neither a true fungicide nor a fertiliser. Some phosphite products currently enjoy fungicide status, having been registered as such after showing some activity against water moulds like Phytophthora. This is misleading.”
Stephen backs up his statement by explaining when phosphites have been tested against true fungal diseases, including septoria in wheat, there’s been no evidence of fungicidal activity. He qualifies this by highlighting the fact that only low doses were tested, which are typical of the doses applied as biostimulants.
“More to the point, we wouldn’t usually try to stimulate plant growth unless the plants in question were completely free of disease,” he adds.
While foliar application of phosphite has been shown to enhance root growth by as much as 50% in a range of plant species, the fact that it can’t be converted into phosphate means it would not technically boost plant growth as fertiliser – at least not in the conventional sense, points out Stephen.
“This means that for a grower looking to fight disease, or provide nutrients for a crop, low dose, early-applied phosphites wouldn’t be the right way to go.”
But Stephen remains confident that biostimulants products actually work. “Our initial work in testing the efficacy of foliar-applied potassium phosphite used a hydroponic system, in which roots were grown in an expanded clay ball matrix (Hydroleca).
“Working in this way allows us to recover the roots easily and means we can readily replicate the trials across multiple treatments. While we do have the traditional bar-charts created from the statistically analysed data, such results are usually best illustrated photographically,” he says.
Sugar beet
In the observations of treated and control roots of winter wheat, winter oilseed rape and sugar beet, the treated plants all clearly showed enhanced root growth.
“This is very exciting, and a clear indicator that we are really onto something with phosphites. Substantial root growth means a stronger, reinforced plant structure, able to withstand more stress and in a better position to produce a high yield come harvest time.”
But Stephen stresses that there is now a need to learn more about how these products work as biostimulants and recently his team was awarded a BBSRC LINK grant to study this.
“With this support we aim to identify exactly what mechanisms phosphites employ to promote root growth. Adopting a multidisciplinary approach, we’ll be bringing a combination of molecular biology, cell biology, plant physiology and CT imaging techniques to the table, allowing us to build a three-dimensional picture of what’s going on.
“Gene expression studies and hormone profiling have already identified several promising fundamental mechanisms which we hope to gain a better understanding of over the course of this project,” he explains
While this lab work is vitally important, Stephen points out that performance in the field is the most important thing for growers to feel confident in using biostimulants to their best advantage Spearheaded by several of the commercial partners within the LINK consortium, on-farm trials have so far seen extremely encouraging results, he points out.
“For example, a pea field experiment in Benwick, Cambridge yielded 5.2t/ha in the untreated control plots and 5.6t/ha in plots treated with OMEX potassium phosphite. To put this in terms we can all understand, for an input of £24/ha, introducing the phosphite produced a yield benefit of £94 – a net profit of £74/ha.
“In a sugar beet trial in South Creake, Norfolk, plots treated with potassium phosphite showed greater ground cover (6%), a higher plant population (12%), and a higher gross yield (31%) when compared with the untreated control,” he says.
So how does Stephen see the future of biostimulants unfolding in UK agriculture? “While we still have a way to go when it comes to proving the efficacy of these intriguing new substances, it’s my firm belief that early growth stage application of low doses of phosphite can significantly enhance root development and greatly improve yield.
“Without acting as a pesticide, early low-dose treatment could therefore lead to better crop establishment and power efficient resource use by crops – spelling a cost-effective benefit in food production at a time when global food safety is of paramount importance,” he says.
But there are wider issues to consider, he adds. “With regulations as they are, currently all agrochemicals must fall into classification as either a fertiliser or pesticide. Registered as a fungicide – but showing no fungicide activity – phosphites could lose their status at any moment. Now is the time to show that we can’t discredit or disregard phosphites, and indeed other biostimulants, just because they don’t fit neatly into a box.
“In fact, with conditions as they are, we need to fight harder than ever to make sure we don’t lose them. Registration as pesticides would also be prohibitively expensive for many small companies that make biostimulants,” he adds.
So what does Stephen believe is the way around this potential stumbling block for biostimulants? “There’s a good argument that biostimulants should be recognised as a new class of agrochemicals. If this isn’t achieved, we’re in danger of losing a whole raft of biostimulants at a time when crop production may need them most,” he concludes.
Biography – Prof Stephen Rossall
Stephen Rossall is an Associate Professor at the School of Biosciences, University of Nottingham and is the author of 34 published scientific papers. He’s a leading researcher on the effects of fungicides and biostimulants and has pioneered the methodology used to research their effects on root architecture and growth. He is passionate about putting science behind biostimulants technology giving a much clearer understanding of how these products work which helps growers reliably utilise them in the field.
