Biofertilizers: A sustainable alternative

The world’s population has been predicted to grow up to 9 billion people by 2050. Therefore, we will need an equivalent increase in agricultural production. The food crisis is expected to be sharp in developing countries. However, it should be considered as a global problem. As the general secretory of the United Nations has said, “The lives of millions of people depend on our collective ability to work. In our world of plenty, there is no excuse for inaction or indifference.”

Researchers have been working to increase food production for decades. Improved crop varieties, chemical fertilizers and pesticides were introduced to keep up with increasing food demands. A major problem with crop plants is their inability to use atmospheric nitrogen gas for their nitrogen requirement. As a result, in early 1900’s methods like the Haber-Bosch process were invented to convert nitrogen gas to ammonia to supply nitrogen to crops in chemical forms.

However, over the decades, use of such fertilizers has caused pollution of soil and water bodies, ultimately affecting human health. Due to the negative effects of using chemical fertilizers, the focus of the research has been shifted towards development of sustainable agricultural practices.

Biofertilizers can provide a cheap and sustainable alternative to reduce the use of chemical fertilizers using biological nitrogen fixation. Biological nitrogen fixation is the conversion of atmospheric nitrogen (N2) to plant utilizable forms such as ammonia with the help of microorganisms. Rhizobia, a type of bacteria found in the soil, are often used to develop biofertilizers. They can exist in a symbiotic relationship with the legume plants and fix N2. Rhizobia can also work as plant growth promoting microorganisms by producing hormones necessary for overall growth of the plant. Even after harvesting, the organic matter left behind add nutrients to the soil and leave enough nitrogen for the next crop to reduce chemical fertilizer usage.

Legumes are plants which have their seeds in pods. Commonly known legumes are soybean, beans, alfalfa, chickpeas, peas, lentils and clover etc. As Legumes have a symbiotic advantage over the cereal crops, they should be promoted in agriculture. Currently, legumes are mainly used for forage in agriculture or as green manure, however, they are an integral part of daily diet in South Asian countries like India, Bangladesh and Pakistan etc.

Legumes are a major source of protein. Products like soy milk and tofu, prepared from soybeans are becoming popular in North America, especially among the people with allergies from dairy products. Due to relatively lower prices and easy production of legume as compared to meats, they can prove to be an excellent source of food in developing countries.

Legumes secrete root exudates which are rich in sugars in the soil around their roots. These nutrient rich exudates attract different microorganisms, creating competition among the microorganisms for food and survival. For rhizobia to survive this competition and enter in symbiosis, they need to utilize a variety of sugars.

A common problem that occurs is the inability of the commercial inoculants to compete for symbiosis in the presence of other indigenous microorganisms in the rhizosphere. Therefore, it is important to study the mechanisms by which different rhizobia utilize a variety of sugars as a carbon source for their metabolism.

The Oresnik lab, at University of Manitoba focuses on understanding the carbon metabolism in rhizobia and our goal is to use our knowledge towards developing better biofertilizers which can survive under field conditions and establish a successful symbiotic association with legume plants. We mainly work with Sinorhizobium meliloti which is a rhizobial species known to form symbiotic association with alfalfa. This association is studied as a model system to understand symbiotic establishment. However, I am specifically interested in understanding the series of events that occur when rhizobia infect the legume roots and the role of carbon metabolism during that interaction.

In conclusion, research scientists are not the only people who can help curb the use of chemical fertilizers. Everyone can contribute by incorporating legumes into their everyday diet. This will supply the average person’s protein requirement, and also help the local farmers. Small changes in our dietary route may not change everything, but we can contribute our fair share towards sustainability and leave a better place for the future generations.

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