Fertilizer

A fertilizer or fertiliser is any material that comes from nature or is made by people. It is put on soil or plant tissues to give plants the food they need to grow. Fertilizers are different from liming materials or other things added to soil that are not food for plants. There are many sources of fertilizer, both from nature and made industrially.

For most modern agricultural practices, people focus on three main foods for plants: nitrogen (N), phosphorus (P), and potassium (K). Farmers use these fertilizers in different ways, such as dry or pelletized forms, with big agricultural equipment, or even using hand-tool methods.

In the past, people used natural things like compost, animal manure, and minerals to help plants grow. But in the 1800s, new discoveries led to making fertilizers in factories. Today, fertilizers help grow enough food for everyone.

History

Main article: History of fertilizer

People have taken care of soil fertility since the first farms were planted. Early farmers in the Middle East, China, Mesoamerica, and the Central Andes used natural materials like minerals or manure to help their crops grow. These methods helped their crops grow better and supported their communities.

Later, scientists studied how plants get nutrients. In the 1800s, an English businessman named John Bennet Lawes tested different manures on plants. He also made his own artificial fertilizer by mixing phosphates with sulfuric acid. In the early 1900s, new ways to make nitrogen fertilizers were invented, such as the Haber process and the Ostwald process. These discoveries changed farming and now help feed many people around the world.

Mechanism

Fertilizers help plants grow by giving them important nutrients. They work in two main ways: by adding nutrients plants need and by making the soil better at holding water and letting air reach plant roots.

Fertilizers usually have three main nutrients called NPK: Nitrogen for leaves and stems, Phosphorus for roots and flowers, and Potassium for strong stems and fruit. They also have small 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. These are called straight fertilizers. Others give more than one nutrient, like both nitrogen and phosphorus. These 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

Making synthetic, or inorganic, fertilizers needs special chemicals. Organic fertilizers come from plants and animals, like excreta, such as urine and feces.

Nitrogen fertilizers are made from ammonia. Ammonia is made using the Haber–Bosch process. Natural gas gives the hydrogen, and nitrogen comes from the air. This ammonia is used to make other nitrogen fertilizers, such as anhydrous ammonium nitrate and urea. Deposits of sodium nitrate in the Atacama Desert in Chile were among the first nitrogen-rich fertilizers and are still mined today.

Phosphate fertilizers come from minerals in phosphate rock, which includes fluorapatite and hydroxyapatite. These minerals are treated with acids to make phosphate salts that plants can use. Potassium fertilizers are made from potash, a mix of potassium minerals. These minerals are cleaned to remove unwanted things like sodium chloride.

NPK fertilizers are a mix of nitrogen (N), phosphorus (P), and potassium (K) fertilizers. They can be made by mixing single fertilizers, using a wet process with liquids and solids, or through the nitrophosphate process, which uses nitric acid on phosphate rock.

Main article: NPK fertilizer

Organic fertilizers come from living or once-living materials, like animal wastes, plant wastes, seaweed, compost, and treated sewage sludge. These can include products from animal processing like bloodmeal, bone meal, and feather meal. Organic fertilizers usually have fewer nutrients and help build healthy soil. Things like peat, coir, bark, and sawdust improve soil structure but do not feed plants directly.

Fertilizer consumption

China makes and uses the most nitrogen fertilizers in the world. Africa uses very little. Fertilizers are very important for farming and chemistry. They are worth about $200 billion. Nitrogen is the most used fertilizer, then 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 help crops grow by giving them important nutrients. How much and when to use fertilizer depends on the type of soil, the crop, and the weather. For example, plants like legumes can get nitrogen from the air, so they usually do not need nitrogen fertilizers.

Fertilizers can be solid or liquid. Solid fertilizers, such as urea and potassium chloride, are easy to store and move. Liquid fertilizers work faster and can be mixed with water for irrigation, a method called fertigation. Some fertilizers release nutrients slowly, which helps reduce waste. Putting fertilizers directly on leaves, called foliar feeding, can also work well, especially for valuable crops like fruits.

Environmental effects

Synthetic fertilizers used in farming can harm the environment. They help cause global warming and can lead to problems like agricultural runoff. This runoff can create dead zones in oceans and contamination in waterways. These fertilizers can also hurt soil health.

To protect the environment, the international community has included food systems in Sustainable Development Goal 2. This goal aims to create a sustainable and climate-friendly food system. Many policies encourage better farming methods, like using less synthetic fertilizer, improving soil management, and using more organic fertilizers.

Policy

In Europe, the European Union helps keep water safe by reducing nitrate levels from fertilizer runoff. Farmers in Britain are encouraged to use better farming methods. In the US, states control pollutants from fertilizer runoff. Some states, like Oregon and Washington, have online databases to track fertilizer chemicals.

China changed its fertilizer subsidies in 2008, which made fertilizer prices go up. This helped large farms use fertilizer more wisely. In 2022, the United States gave $250 million to help local fertilizer production. The European Union is also working to improve how fertilizer is made and used because of rising energy and fertilizer prices.