Fertilizer

Fertilizer is any material applied to soil or plant tissues to supply essential nutrients.

These materials are vital for supporting plant life and increasing agricultural productivity. Fertilizers can be of natural or synthetic origin. They are often distinguished from liming materials, which are non-nutrient soil amendments. By providing specific elements, fertilizers allow crops to grow more efficiently. This process is a cornerstone of modern global food systems.

Most modern agriculture focuses on three primary macronutrients known as NPK.

Nitrogen (N) is essential for the growth of leaves and stems. Phosphorus (P) supports the development of roots, flowers, seeds, and fruit. Potassium (K) promotes strong stem growth and the movement of water within the plant. Plants also require secondary macronutrients, including calcium (Ca), magnesium (Mg), and sulfur (S). Additionally, they need micronutrients like iron (Fe), zinc (Zn), and boron (B) in smaller amounts.

Fertilizers are classified into several distinct categories based on their composition and origin. Organic fertilizers are derived from recycled plant or animal matter, such as compost or manure.

Inorganic fertilizers are often called synthetic fertilizers because they require chemical manufacturing. These are typically made from minerals or industrial processes. Fertilizers can also be "straight," meaning they provide only a single nutrient. Conversely, "complex" or multinutrient fertilizers provide two or more nutrients at once. This variety allows farmers to tailor applications to specific crop needs.

Managing soil fertility has been a priority since the dawn of agriculture. Early societies in the Middle East, China, and the Andes used natural methods to enhance crops. Egyptians, Romans, and Babylonians also utilized minerals and manure to increase yields. In 1837, John Bennet Lawes began experimenting with manures in pots. By 1842, he patented a process using phosphates and sulfuric acid. This invention helped launch the first artificial manure industry.

The 20th century brought massive changes through chemical innovations. The Haber process produces ammonia (NH3) using methane and nitrogen from the air.

This ammonia can then be converted into nitric acid through the Ostwald process. These breakthroughs allowed for the large-scale production of nitrogen fertilizers. This helped drive the "Green Revolution," which increased global food productivity. It is estimated that synthetic nitrogen fertilizer supports nearly half of the world's population.

Global fertilizer use is distributed unevenly across different regions. In 2021, Asia accounted for 53% of the world's total agricultural inorganic fertilizer use. The Americas used 29%, followed by Europe at 12%, Africa at 4%, and Oceania at 2%.

Within these regions, China, India, Brazil, and the United States are the largest users. China stands as the largest user of each individual nutrient. The scale of production is immense, with nitrogen use rising nearly 20-fold between 1961 and 2019. In 2003 alone, nitrogen use reached a rate of 100 million tonnes per year.

While fertilizers are necessary for food, they can cause environmental challenges. Excessive application can lead to nutrient runoff, where fertilizers wash into water bodies.

This process can cause eutrophication, which leads to harmful algal blooms. Such blooms can create aquatic dead zones in rivers and seas.

Furthermore, the chemical production of fertilizers results in carbon and other emissions. Some fertilizers may also contain heavy metals from mining processes. To mitigate these effects, farmers use sustainable practices like planting buffer strips to catch runoff.