The market is currently awash with biostimulants, with over 300 products currently available in the UK. There’s such a vast range of different types that’s it’s pretty difficult for to know what’s what, what it’s supposed to do and when to apply it. Most of us recognise amino acids, seaweeds and phosphites, but beyond these main groups it’s becoming increasingly difficult to keep up with this market that’s developing apace. It’s going to be a steep learning curve.

Biostimulation is a confusing arena, despite a ‘supposed’ agreement on the standard definition under the new European Fertilising Products Regulation (EFPR). This will come into force in 2022 – although there appears to be some doubt that timescale will be achieved – and sets out a new procedure for authorising biostimulants in agriculture.

The upshot is that biostimulants will be required to undergo an assessment process and the end result will be a product bearing the CE mark. This will mean any label claims must be scientifically proven and relate to the processes which come within the definition of a biostimulant, such as improved efficiency of nutrient use, enhanced tolerance to abiotic stress, better crop quality traits, or improved availability of confined nutrients in the soil, rhizosphere or phyllosphere (the above ground parts of the plant).

There’s a big disconnect in the UK at the moment and in the field, it can be hard to identify whether biostimulants are having an effect. In the lab, however, the science seems to stack up and there is undeniably some potential in this class of product. Part of the problem seems to me that we’ve got used to assessing the merits of products in a black and white way. Biostimulants often contain a multitude of substances which may influence a number of biochemical pathways so sit firmly in the grey.

One of the things I think we’re going to learn as the industry gradually steps away from a system of growing crops dependent on crop protection products, is that some of the things that have been considered in a binary way are anything but. Take disease control – in the mainstream the current strategy is to apply a fungicide programme to keep the leaves which contribute most to yield as green as possible. Yet science is now revealing that some of the fungal organisms we consider solely from a pathogenic point of view can also exist in a mutualistic or symbiotic way in plant tissues for a long period, only becoming pathogenic when triggered – ramularia and rhynchosporium are examples of diseases where the causal organism changes its trophic state.

Gene-sequencing techniques are beginning to provide an insight into the complex relationship between the communities that make up the microbiome of the leaf and it’s going to be fascinating to see what this work reveals and where it leads in the future – which is likely to be towards a more sustainable system for disease control. ‘Brewing biology’ is already being practised by a few growers at the forefront of developing farming systems less reliant on crop protection chemistry, but to understand better how manipulating the microbiome can prevent disease is a very exciting prospect.

Coming back to biostimulants, it strikes me that these studies may also help our understanding of why results with these products are sometimes variable in the field. Better understanding the plant-microbiome relationships in the above ground parts of the plant could well explain one of the reasons why biostimulants don’t always influence the plant as expected. Could the function of some biostimulants be compromised by fungicides because of the effect they’re having on the microbiome? It’s an interesting thought.

There are some really interesting developments going on in this mysterious world of biostimulants that could help reduce the reliance on nitrogen fertilisers and reduce crop production’s carbon footprint. There’s also the potential to help agriculture become less independent on the chemistry that’s characterised crop production for decades. It’s become an arms race, where nature overcomes chemistry, new chemistry comes along to shift the balance and so it goes on, but it’s a dead cert nature will win in the end. After all, as Einstein said, insanity is to do the same thing over and over again and expect different results, so perhaps it’s time to become less black and white.

Based in Ludlow, Shrops, CPM technical editor Lucy de la Pasture has worked as an agronomist. @Lucy_delaP