Fertilizer

A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers help plants grow by giving them the food they need. They are different from liming materials or other non-nutrient soil amendments. There are many sources of fertilizer, both natural and industrially produced.

For most modern agricultural practices, fertilization focuses on three main macronutrients: nitrogen (N), phosphorus (P), and potassium (K). Farmers apply these fertilizers in different ways, such as using dry or pelletized or liquid methods, large agricultural equipment, or even hand-tool methods.

Historically, people used natural sources like compost, animal manure, and harvested minerals to help plants grow. But in the 19th century, new discoveries led to the creation of synthetic agrochemical fertilizers, changing how food is grown around the world. Today, fertilizers play a big role in producing enough food for everyone.

History

Main article: History of fertilizer

People have been taking care of soil fertility since the very first farms were planted. Early farmers in places like the Middle East, China, Mesoamerica, and the Central Andes used natural materials like minerals or manure to help their crops grow better. These methods gave them an edge over others and helped their societies grow.

Later, scientists began studying how plants get their nutrients. In the 1800s, an English businessman named John Bennet Lawes started testing different manures on plants. He even made his own artificial fertilizer by mixing phosphates with sulfuric acid. In the early 1900s, new ways to make nitrogen fertilizers were invented, like the Haber process and the Ostwald process. These discoveries changed farming forever and now help feed much of the world.

Mechanism

Fertilizers help plants grow by providing important nutrients. They work in two main ways: by adding nutrients plants need and by improving the soil so it holds water better and allows air to reach plant roots.

Fertilizers usually contain three main nutrients called NPK: Nitrogen for leaves and stems, Phosphorus for roots and flowers, and Potassium for strong stems and fruit. They also include smaller amounts of other nutrients like copper, iron, and zinc. These nutrients help plants stay healthy and grow well.

Classification

Fertilizers can be grouped in different ways. Some give just one kind of nutrient, like nitrogen or phosphorus, and are called straight fertilizers. Others give more than one nutrient, like both nitrogen and phosphorus, and are called multinutrient or complex fertilizers. Fertilizers are also split into organic and inorganic types. Organic fertilizers come from plants or animals, like compost or manure. Inorganic fertilizers are made through chemical processes and often don’t contain carbon, except for a common one called urea.

Straight fertilizers include ammonia, which provides nitrogen, and superphosphates, which provide phosphorus. One common potassium fertilizer is muriate of potash. Multinutrient fertilizers mix nitrogen, phosphorus, and potassium together. These are often labeled with three numbers, like 10-10-10, showing the amounts of each nutrient. There are also special tiny nutrients, called micronutrients, that plants need in very small amounts, such as zinc, iron, and manganese.

Production

The production of synthetic, or inorganic, fertilizers requires prepared chemicals, whereas organic fertilizers come from the biological processing of plant and animal remains or excreta, like urine and feces.

Nitrogen fertilizers are made from ammonia, which is produced by the Haber–Bosch process. In this process, natural gas usually supplies the hydrogen, and nitrogen is taken from the air. This ammonia is then used to make other nitrogen fertilizers, such as anhydrous ammonium nitrate and urea. Deposits of sodium nitrate, found in the Atacama Desert in Chile, were one of the first nitrogen-rich fertilizers used and are still mined today.

Phosphate fertilizers are obtained by extracting minerals from phosphate rock, which contains fluorapatite and hydroxyapatite. These minerals are treated with acids to create water-soluble phosphate salts. Potassium fertilizers are made from potash, a mixture of potassium minerals, which are purified to remove unwanted substances like sodium chloride.

NPK fertilizers are a mix of nitrogen (N), phosphorus (P), and potassium (K) fertilizers. They can be made by blending individual fertilizers, using a wet process with liquid and solid materials, or through the nitrophosphate process, which involves treating phosphate rock with nitric acid.

Main article: NPK fertilizer

Organic fertilizers come from living or formerly living materials, such as animal wastes, plant wastes, seaweed, compost, and treated sewage sludge. These can include products from animal slaughters like bloodmeal, bone meal, and feather meal. Organic fertilizers often contain less-concentrated nutrients and are used to build soil health. Materials like peat, coir, bark, and sawdust are used to improve soil structure but do not provide direct nutritional value to plants.

Fertilizer consumption

China is now the biggest producer and user of nitrogen fertilizers, while Africa uses very little. Fertilizers are important in farming and chemistry, worth about $200 billion. Nitrogen is the most used fertilizer in the world, followed by potash and phosphate.

Potash is mainly made in Canada, Russia, and Belarus. In the United States, more fertilizer is used than there is farmland. The European Union used the most fertilizer in 2017, but the amount has gone down since then. In 2020, EU countries used about 70 kilograms of fertilizer for every hectare of farmland. Data on fertilizer use can be found from The World Bank.

Application

Fertilizers are used to help crops grow by providing important nutrients. The amount and timing of fertilizer use depend on the type of soil, the specific crop, and weather conditions. For example, plants that can take nitrogen from the air, like legumes, usually do not need nitrogen fertilizers.

Fertilizers can be applied in both solid and liquid forms. Solid fertilizers, such as urea and potassium chloride, are common and easy to store and transport. Liquid fertilizers work faster and can be mixed with irrigation water, a method called fertigation. Some fertilizers are designed to release nutrients slowly over time, which can help reduce waste and pollution. Applying fertilizers directly to leaves, known as foliar feeding, can also be effective, especially for valuable crops like fruits.

Environmental effects

Synthetic fertilizers used in agriculture have wide-reaching environmental consequences. They contribute to global warming and can lead to problems like agricultural runoff, which causes ocean dead zones and waterway contamination. They also affect soil health and can accumulate toxic compounds in ecosystems.

To help protect the environment, the international community has included food systems in Sustainable Development Goal 2. This goal focuses on creating a climate-friendly and sustainable food production system. Many policies aim to shift agricultural practices toward more sustainable methods, such as using less synthetic fertilizer, better soil management, and more organic fertilizers.

Policy

In Europe, the European Union's Nitrates Directive helps reduce high nitrate levels in water runoff. Farmers in Britain are encouraged to use more sustainable farming practices. In the US, states regulate pollutants from fertilizer runoff, and some, like Oregon and Washington, have online databases to track fertilizer chemicals.

China reduced some fertilizer subsidies in 2008, which increased fertilizer prices and led large farms to use fertilizer more efficiently. In 2022, the United States announced a $250 million grant to support local fertilizer production. The European Union has also focused on improving fertilizer production and use due to recent increases in energy and fertilizer prices.