AGH scientists developed and examined fertilisers biodegradable in 100%

Structure of the fertiliser just after being produced. Photography from the archives of the Department of Biomaterials and Composites

Structure of the fertiliser after two months in soil with noticeable decay of the polymer matrix. Photography from the archives of the Department of Biomaterials and Composites

How to slow down soil erosion on Earth, stop soil depletion and degradation, meet the increasing demand for plant-based products, enrich soil with nutrients without increasing nitrogen or phosphorus content – these are just some of the questions the scientists from AGH in Krakow are trying to answer.

As part of the works carried out at the Faculty of Materials Science and Ceramics at the Department of Biomaterials and Composites, research on new generation fertilisers is being conducted. CRFs (controlled release fertilisers) are fertilisers that contain biogenic components available in a form a plant cannot immediately absorb. They are usually coated with materials that allow for the control of, inter alia, the rate and time of nutrient release. The ability to control the release of substances is the main factor that distinguishes CRF fertilisers from those traditionally applied. AGH research allowed the scientists to optimise the process of producing such fertilisers, as well as examine and assess their properties by comparing them to analogous conventional mineral fertilisers.

The properties of the designed CRF-AGH fertilisers were examined on the basis of the cultivation of various plants, including Phacelia honey, oats or millet, in laboratory conditions. We simulated rainfall on the crops and based on the water that flowed through the soil and later collected in a sealed container, we determined the concentration of salt that was washed out of the soil – explains one of the authors of the research, Piotr Szatkowski, DSc.

The results of the simulation of the rainfall and the water washed out salts show that the salt concentration in samples with commercial fertiliser is at significantly higher level. After the rainfall simulation was completed, the plants were harvested and examined.

– On the basis of the examination, we found that plants for which no fertilisers were used were clearly more fragile and brittle. What is more, they had a less intense colour, which would indicate deficiency of nutritional components. The plants grown on the fertilised soil-based substrate were in much better condition. However, the crops for which CRF was used showed a greater stem thickness and a more intense and distinctive colour - adds Katarzyna Suchorowiec, the student of the AGH Faculty of Materials Science and Ceramics.

In addition, plants fertilised with CRF had a greater ability to accumulate water compared to those grown on other substrates.

  Three images from an optical microscope. On each of them, in the central part, a close-up of the green, transverse strip. In the middle photo, a similar element is dark green, on the left and right a shade of green slightly lighter.

Optical microscope images showing plant fragments from the left: without fertiliser, with CRF fertiliser and with commercial fertiliser

Moreover, CRF fertilisers give the grounds to believe in bringing promising effects when it comes to their use for fertilising plants growing in water. It is a great opportunity, especially when considering that fertilising this type of plants has been earlier significantly limited and burdensome in view of the occurrence of a sudden increase in the concentration of mineral salts in the water. In order to investigate the rate of salt release, tests of CRF-AGH fertilisers in water were carried out. On the basis of the obtained results, it was found that both in the initial phase and after a longer period, CRF-AGH fertilisers gradually release the salts retained in them. These fertilisers proportionally released their salts to water, which means that at the same time intervals the concentration increased by the same value. Such constructed fertilisers would enable precise fertilisation of plants growing in water, e.g. rice. It would also entail much less interference with the natural environment, both in the fields and in their vicinity.

The conclusions from the research conducted by AGH scientists indicate that an alternative method of fertilisation is the use of fertilisers with a controlled release of microelements. These types of fertilisers would slowly release nutrients into the soil. Consequently, plants would have continuous access to micronutrients, which, in turn, ensure their sustainable growth and development. In addition, slow and controlled release fertilisers would be able to prevent nutrients leaching from the soil, which could occur during heavy rainfall. An additional advantage of controlled release fertilisers is the possibility of applying them not only for fertilising crops of plants growing in the soil, but also as a source of valuable elements for the plants grown in water. Owing to additional coating, the salts contained in the fertiliser seep into water at a much slower pace, and plants are not exposed to the effects of a sudden increase in their concentration.