Biologicals: What the perspectives are

There are high political and social demands on agriculture. In addition, there are the economic problems, such as those triggered by the war in Ukraine or the recent removal of subsidies. The increasing effects of climate change are also making secure agricultural production more difficult. However, these growing challenges also offer opportunities for innovation. The role that biologicals can play in this remains to be seen in the coming years. This is because the sometimes fantastic positive yield effects in the area of special crops, in greenhouse cultivation or in tropical and subtropical climate zones cannot be directly transferred to our temperate climate zone and certainly not to the open field. The promises of large yield increases or savings in other production resources such as fertilizer or plant protection should therefore be critically questioned.

Biologicals are generally intended to promote growth, nutrient appropriation and the resistance of crops to stress factors and plant diseases. The term includes "biological plant protection products", i.e. plant protection products of natural origin. This group includes bioidentically produced substances, fungi, bacteria, viruses, pheromones and also inorganic substances of natural origin such as minerals. There are also plant biostimulants, which consist of natural or synthetic substances and microorganisms. They are in turn divided into microbial and non-microbial biostimulants. So far, Azotobacter, Rhizobium and Azospirillum species and mycorrhizal fungi have been approved as microbial biostimulants.

Chemical plant protection products are primarily intended to control pests, diseases and weeds and are therefore effective against biotic factors. In contrast, when biostimulants are applied to plants or the soil, they aim to improve growth and yield formation by strengthening natural defense mechanisms and increasing tolerance to abiotic stress factors such as drought, herbicide stress, salt stress or temperature fluctuations.

In contrast to chemical plant protection products, which can have negative effects on the environment and non-target organisms, especially if used incorrectly, biostimulants are generally more environmentally friendly. However, they can in no way be a substitute for chemical pesticides. Their use in agriculture should rather be seen as a supplement in order to achieve optimum yields with strengthened plants.

The regulation came into force on July 16, 2022, and its introduction also changed the requirements. The CE marking for fertilizer products was introduced for the first time for agricultural inputs. The previously known system of fertilizer types was abolished and replaced by a new system for placing fertilizer products on the market. These changes required a rethink on the part of farmers, retailers and producers. The following information must be provided for CE marking in accordance with the EU Fertilizer Regulation:

• Physical form
• Date of manufacture and expiry date
• Method(s) of application
• Effect for each target plant
• Any relevant instructions relating to the efficacy of the product, including soil management practices, chemical fertilization, incompatibility with plant protection products, recommended spray nozzle size, recommended spray pressure and other drift mitigation measures.

External and independent conformity assessment bodies are required to check the criteria for CE certification. Various bodies in Europe are accredited for this purpose. A list of these bodies can be found in the EU Commission's NANDO database.

The Julius Kühn Institute (JKI) has set up its own conformity assessment body for Germany. However, products that have already been approved by other means in the past can still be marketed as plant additives, organic fertilizers or soil improvers in the future. However, it is probably only a matter of time before these products are voluntarily CE-certified. As a certain degree of certainty of effectiveness and therefore a quality statement is associated with this.

The starting point is a natural, but to a large extent not yet fully researched process in higher plants, namely the reaction to stress and the resulting "hardening" or "stress priming" against the recurrence of such stress. It works as follows: When a plant is exposed to an abiotic stress, it reacts with a stress response (osmotic/oxidative stress). Cell constituents and free radicals are released. These lead to cell damage, but also have a signaling effect for the plant. If the stress is not too great, the plant's signaling pathways are activated and it adapts to the stress. The type of stress adaptation can vary greatly and ranges from increased root/shoot growth to the formation of protective substances and radical detoxification. If the abiotic stress is only moderate, stress priming can occur and if the stress recurs, the plant can react with a faster stress adaptation. When biostimulants are applied to a non-stressed plant, ideally under growing conditions, the signaling pathways are activated and stress priming occurs in this way.

It is very important to note that a corresponding stress adaptation is only possible with an adequate supply of micronutrients. For example, the micronutrients Fe, Zn, Mn and Cu are essential for radical detoxification. Many other stress adaptations are also based on enzymes that require certain micronutrients as cofactors. It should also be noted that biostimulants are generally not able to cure damage that has occurred.

For microbial biostimulants, it is particularly important to find suitable living conditions during the colonization phase. For products that act via the soil or the plant root, conditions should be present that allow unimpaired root growth. As a result, non-microbial biostimulants appear to be somewhat more flexible in their application. However, here too, the application conditions have a much greater influence on the possible effect than is the case with many synthetic chemical plant protection products! The appropriate products must therefore be applied in good time before the stress occurs. The effect to be expected from a biostimulant application can therefore only ever be a stress priming of the plant for future abiotic stress or a general improvement in resistance, growth promotion and higher nutrient appropriation. Accordingly, the application must take place as early as possible before the effect of a potential abiotic stressor. In the literature and in trials carried out by BAT Agrar, there were indications that varieties react differently to the various products. In these trials, effects were also found in maize rather than in winter wheat.