The Discovery of Nitrogen Fixation: How Plants Get the Nitrogen They Need

Nitrogen is an essential element for plant life, but it’s not always easy for plants to get the nitrogen they need. Nitrogen is so important for plant growth that it is considered the “limiting factor” for many agricultural crops. But plants have a neat trick at their disposal, known as “nitrogen fixation,” which allows them to scavenge the nitrogen they need from the atmosphere. In this article, we’ll explore how the process of nitrogen fixation was discovered and how it works.

Understanding the Basics of Nitrogen Fixation

Nitrogen fixation is the process by which plants, bacteria and some other organisms like algae convert nitrogen from the atmosphere into a form that plants can utilize. Nitrogen is a major constituent of the atmosphere, making up around 78% of it. But this nitrogen gas is inert and cannot be used directly by plants. Instead, plants must convert nitrogen into chemicals like nitrates, which can be absorbed through the roots and used to produce proteins, enzymes, hormones and other essential building blocks for growth and survival.

The Discovery of Nitrogen Fixation

Nitrogen fixation was discovered by German chemist, Hermann Hellriegel, and Dutch botanist, Willem Van Evanderk, in the late 1800s. The two researchers had long been studying the relationship between soil and plant health. Through their work, they discovered that legumes such as clover and alfalfa were able to extract nitrogen from the atmosphere and use it to boost their growth.

Their experiments sparked a wider interest in the process of nitrogen fixation and decades of research followed, trying to uncover the exact mechanism behind it. In 1901, a French scientist named Sergei Winogradsky discovered the role of nitrogen fixing bacteria. He noticed that certain species of soil-dwelling bacteria, like those belonging to the genus Rhizobium, took up nitrogen gas and converted it into nitrates.

In more recent years, our understanding of the nitrogen cycle and how different nitrogen compounds interact with plants has grown exponentially. Even so, nitrogen fixation through microbial activity still forms the foundation of our understanding of plant nutrition.

Exploring the Process of Nitrogen Fixation

Nitrogen fixation occurs both naturally and through the use of agricultural practices. In the wild, nitrogen fixation is performed by several different types of bacteria. These bacteria have the ability to convert atmospheric nitrogen gas into nitrates, which can be absorbed by plants and used for growth.

Biological nitrogen fixation is most commonly done by symbiotic bacteria, which form a mutualistic relationship with their host. In legumes, for example, the bacteria Bradyrhizobium japonicum takes up residence inside the plants’ root nodules and begins to convert nitrogen into nitrates. In exchange, the plants provide the bacteria with carbohydrates and other nutrients.

Aside from bacteria, some other microbes are also able to perform nitrogen fixation, albeit in less effective ways. Blue-green algae, like Anabaena and Nostoc, can also capture nitrogen from the air and convert it into nitrates through their metabolic processes. Human intervention and agricultural practices can also be used to increase the rate of nitrogen fixation.

Uses of Nitrogen Fixation in Agriculture

Understanding the process of nitrogen fixation has helped to increase crop yields around the world significantly. In agricultural systems, nitrogen-fixing crops, such as soybeans and legumes, are planted to replenish the soil with much-needed nitrogen. These crops have the added benefit of providing a sustainable source of food for animals and humans, as well as increasing soil fertility.

Additionally, agricultural practices such as crop rotation and the use of nitrogen-fixing bacteria in fertilizer for soils can also be used to boost nitrogen levels and increase yields. In organic farming, bacteria, such as Rhizobium, are used as an alternative to synthetic fertilizers.

Nitrogen fixation is an incredibly important process for plant growth and survival. Through the discovery of nitrogen fixation by Hermann Hellriegel and Willem Van Evanderk, humans are now able to understand and use this process to increase crop yields and soil fertility. In the wild, bacteria like those in the genus Rhizobium are able to convert atmospheric nitrogen into nitrates, while agricultural practices like the use of nitrogen-fixing crops and bacteria can increase the rate of nitrogen fixation.

By understanding and utilizing the process of nitrogen fixation, we can ensure that our crops and soils get the nitrogen they need to thrive.