India’s agricultural yield has seen a steady increase over the years, thanks to the use of science and technology in crop practices. One such method is the use of chemical fertilisers, which momentarily improved crop yields. However, their reckless use has resulted in the severe degradation of the environment and economic losses to farmers as they run off with water or are unavailable to crops. In a recent study, researchers at the Indian Institute of Technology, Kanpur, led by Prof. Nishith Verma, have developed a biomolecule-based fertiliser that can help address the drawbacks of chemical fertilisers.

Many species of bacteria, fungi and algae act as natural fertilisers as they increase the soil nutrients and make it readily available for plants to absorb. As they are biological in origin, these 'bio-fertilisers' do not harm the plants or the environment. Rhizobacteria are one such bio-fertilisers that live in the roots of plants and promote their growth. They secrete biomolecules like N-acetyl homoserine lactones, which act as signals for communication among the bacteria living in the roots of the plants. They also regulate plant growth and increase the ability of plants to withstand diseases.

On the flip side, these biomolecules are unstable in the soil and quickly degrade, becoming unavailable to plants. In the current study, the researchers have attempted to develop a stable substrate, using iron-carbon nanofibres, to help deliver these biomolecules. The combination of the substrate and the biomolecules were found to be conducive to plant growth and its ability to fight infections. The study was published in the journal Environmental Science: Nano and was funded by the Council for Scientific and Industrial Research (CSIR).

The researchers grew the iron-carbon nanofibres by infusing iron on activated carbon fiber (a highly porous material with excellent absorbing properties) and powdering it. They then allowed this powder to interact with the biomolecule N-acetyl homoserine lactone, resulting in the nano bio-composite. The researchers tested the stability and the role of the bio-composite in plant growth by studying germination and growth of chickpea seeds, on which the bio-composite was used.

“The iron-carbon nanofibers in the nanocomposite serves dual roles. It acts as a substrate for the biomolecule N-acetyl homoserine lactones, thereby protecting them from enzymatic degradation, and as a carrier of these biomolecules to plant cells via roots and shoots”, says Mr. Arun Kumar from IIT Kanpur, who is an author of the study.

The study found a massive 116% increase per day in the germination rate of seeds and almost a four-fold increase in the length of the seedlings that were grown using the bio-composite. This increase was also seen when the plants were subjected to oxidative stress and salinity. Besides, there was also a substantial increase in the length of the root hairs, the extent of the outer layers of the leaf or leaf canopy, wet biomass, chlorophyll levels and protein content of the plant.

“The plant growth increased because of the increase in the moisture carried from the roots to the pores in the leaves, where it is released as water vapour. This increased transpiration resulted in increased chlorophyll and protein contents of the plant. Increase in chlorophyll indicated the growth of plant cells by increased photosynthetic activity”, explains Prof. Verma on the findings.

The researchers also found that the iron-carbon bio-composite protected the plants from fungal infections like rusts and anthracnose. Plants treated with the bio-composite had shiny green leaves, which otherwise would have turned into yellow and curled up due to the disease.

The findings of the study show that the bio-composite can successfully replace chemical fertilisers. Although the researchers have not analysed its cost benefits, they estimate that the production cost of the bio-composite could be ten times less than chemical fertilisers. Besides, it takes only a small amount of the bio-composite, applied just once, for a good yield, while chemical fertilisers need to be used at least thrice in the life cycle of the plant. Since the bio-composite is organic in nature, it does not pose any threat to the environment or other plants.

As a next step, the researchers are now testing the efficiency of the bio-composite, outside the controlled atmosphere of a lab, on a small plot in the gardens of their institute.

“We are now testing the material in the garden of IITK, where a small plot is prepared and cultivation of chickpeas are being done in natural environment. During this pilot level of the project grains yield will also be recorded. After getting positive results of this pilot level projects, we have plans to test the material for wheat crop”, concludes Mr. Kumar.

Editor's Note: This article was edited to correct a grammatical mistake. The error was regretted.