Film coating of seeds – Benefits and challenges

As populations grow and competition for fertile land increases, agronomists are continually challenged with producing more food with fewer resources. Since 1968, Incotec has contributed to sustainable agriculture by providing innovative technologies that boost the yield of seeds. With the recent acquisition of Incotec by Croda, a speciality chemical manufacturer, an even broader and more innovative portfolio of seed enhancement products becomes available to customers. Incotec’s film coating is a good illustration of a technology initially applied to vegetable seeds, for which the knowledge and experience have progressively been extended during the last 10 years to tackle the specific challenges of large volume field crops.

Incotec researchers are often asked why seeds need to be coated in the first place. To answer this, it is worthwhile taking a step back to explain the added value of seed treatments in general. Disease and insect pressure can reduce yield and cause spoilage. The application of plant protection products (PPPs) directly onto the seeds prior to sowing enables precise and efficient protection of the seed and of the resulting seedling during the early stages of its growth. In this way, seed treatment enables significant reduction of the amount of crop protectants used, estimated to be as much as 80-90% when compared to furrow or spray applications. The addition of a film coat formulation along with PPPs during the seed treatment process brings about additional benefits: it binds the PPPs onto the seeds to allow an excellent retention of the active, reducing dust emissions and making them safer for seed treatment operators, growers and non-target organisms, and it greatly improves processability, plantability and cosmetics in comparison to seeds treated with PPPs without additional film coat product. Another benefit is that it enables application of controlled amounts of nutrients.

By far the biggest challenge in the development of film coat is the vast variability of the systems being coated. On the one hand, every seed species and every seed cultivar within a given species displays its own size, shape and surface properties that translate into specific technical requirements for the coating to fulfill its key functions. On the other hand, the broad range of crop protectants registered for seed enhancement applications brings about an extra level of complexity: considering that every PPP formulation interacts with the coating components in its own way and that seed treatment slurries generally combine several PPPs with a film coat product, the number of combinations is endless! To tackle these needs in the best possible way, the Incotec R&D team generally develops film coat formulations for specific crops, targeting superior properties for the broadest possible range of varieties within a given species and for the main PPP slurries used in the seed treatment industry. In some cases, film coat products may be tailored for a customer to fulfill unmet needs, ranging from a special colour for their coated seeds to problematic PPP slurry or a seed variety that is difficult to coat. The two following examples offer a good illustration of how challenges of the seed treatment process have been addressed by Incotec.

Corn (maize) is one of the best examples of a crop with its very own specificity: the smooth and waxy surface of its seeds often limits the adhesion of the coating and complicates their processing in large seed treatment facilities. Indeed, immediately after the application of the film coating treatment, corn seeds undergo a great deal of mechanical stress during transport from the rotary coater to the silo or bagging line. This generally results in abrasion of the film coating layer to a greater or lesser degree depending on the length and configuration of the post-treatment handling of the seeds. The risk of abrasion remains when the coating is fully dry, for instance during further transportation and upon sowing. This does not only impact the cosmetic appearance of the coated seeds, it also gives rise to loss of active ingredients, which is detrimental to the seed protection efficiency and, even more importantly, to the safety of seed treatment operators, growers and non-target organisms in the field. To complicate matters, some PPP packages are more prone to causing abrasion issues than others, and several key seed characteristics influence the extent of abrasion: these include size, shape and seed-surface wax content. Incotec's new red film coat product Disco AG Red L-450 addresses these specific needs for corn seed treatment by offering excellent coating coverage, abrasion resistance and dust control, as well as very good flow and plantability properties, tested and confirmed on a wide range of corn seed varieties and PPP cocktails.

Another major challenge, generally relevant to all seed species, is the drying of the coating layer, which must be as quick as possible to maintain an efficient seed treatment process. Incomplete drying of the coated seeds is certainly one of the worst case scenarios at a seed treatment plant. It will unavoidably result in poor flowability or even extensive clumping of the coated seeds, giving rise to fouling and blocking of the treatment line and, consequently, will require additional manpower, time and costs for cleaning the machinery. Additionally, considering the increasing need to apply high PPP slurry volumes onto the seeds to optimise the available ‘seed space’, the added value of fast drying film coating systems becomes even more evident. In the case of vegetable seeds, which are coated in relatively small volumes, the use of integrated temperature and humidity controls, in rotary dry coaters for instance, combined with Incotec’s Disco Advanced film coat product range, have enabled application of higher slurry volumes and thicker coating layers onto the seeds with an optimal processing time. For field crops, with considerable tonnages of seeds being treated per hour, the use of drying systems integrated to the coating equipment is generally excluded, although the addition of finishing powder directly after the PPP slurry application via integrated powder feeders greatly accelerates the coating process by decreasing the tackiness of the freshly coated seeds.

The new clear film coat product Disco AG L-650 was specifically designed by Incotec to improve the drying of large volume treated seeds by preventing their clumping directly after coating and significantly increasing their wet and dry flowability compared to standard film coat products. Initially developed for soybean and corn, it has shown superior performance on a broad range of seeds species and varieties in combination with the majority of PPP packages used in the seed industry.

Looking at current and future trends in film coating technology, the compatibility of the formulation with beneficial microorganisms is already at the centre of film coat developments. The aim is to ensure a high survival rate of the biologicals, when combined with the coating in both liquid and dry states. Additionally, the increasing awareness of the environmental impact of products throughout their life cycle will trigger more focus on the sustainability of formulations. Finally, along with the ever-increasing performance of film coat products in terms of dust control, abrasion resistance or drying, the development of novel analytical methods is essential for a precise characterisation of the improvements of future developments in this technology. Combining Croda’s formulation know-how with Incotec’s expertise in seed enhancement technologies will most definitely accelerate the research towards solutions to these key challenges.


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