9 24 24 Fertilizer

[Kerrie Gingrich]

Afertilizer (American English) or fertiliser (British English) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Many sources of fertilizer exist, both natural and industrially produced.[1] For most modern agricultural practices, fertilization focuses on three main macro nutrients: nitrogen (N), phosphorus (P), and potassium (K) with occasional addition of supplements like rock flour for micronutrients. Farmers apply these fertilizers in a variety of ways: through dry or pelletized or liquid application processes, using large agricultural equipment or hand-tool methods.

Historically fertilization came from natural or organic sources: compost, animal manure, human manure, harvested minerals, crop rotations and byproducts of human-nature industries (i.e. fish processing waste, or bloodmeal from animal slaughter). However, starting in the 19th century, after innovations in plant nutrition, an agricultural industry developed around synthetically created fertilizers. This transition was important in transforming the global food system, allowing for larger-scale industrial agriculture with large crop yields.

Nitrogen-fixing chemical processes, such as the Haber process invented at the beginning of the 20th century, and amplified by production capacity created during World War II, led to a boom in using nitrogen fertilizers.[2] In the latter half of the 20th century, increased use of nitrogen fertilizers (800% increase between 1961 and 2019) has been a crucial component of the increased productivity of conventional food systems (more than 30% per capita) as part of the so-called "Green Revolution".[3]

The use of artificial and industrially-applied fertilizers has caused environmental consequences such as water pollution and eutrophication due to nutritional runoff; carbon and other emissions from fertilizer production and mining; and contamination and pollution of soil. Various sustainable-agriculture practices can be implemented to reduce the adverse environmental effects of fertilizer and pesticide use as well as other environmental damage caused by industrial agriculture.

Management of soil fertility has preoccupied farmers since the beginning of agriculture. Middle Eastern, Chinese, Mesoamerican, and Cultures of the Central Andes were all early adopters of agriculture. This is thought to have led to their cultures growing faster in population which allowed an exportation of culture to neighboring hunter gatherer groups. Fertilizer use along with agriculture allowed some of these early societies a critical advantage over their neighbors, leading them to become dominant cultures in their respective regions (P Bellwood - 2023[6])[7]. Egyptians, Romans, Babylonians, and early Germans are all recorded as using minerals or manure to enhance the productivity of their farms.[1] The scientific research of plant nutrition started well before the work of German chemist Justus von Liebig although his name is most mentioned as the "father of the fertilizer industry".[8] Nicolas Thodore de Saussure and scientific colleagues at the time were quick to disprove the simplifications of von Liebig. Prominent scientists on whom von Liebig drew were Carl Ludwig Sprenger and Hermann Hellriegel. In this field, a 'knowledge erosion'[9] took place, partly driven by an intermingling of economics and research.[10] John Bennet Lawes, an English entrepreneur, began to experiment on the effects of various manures on plants growing in pots in 1837, and a year or two later the experiments were extended to crops in the field. One immediate consequence was that in 1842 he patented a manure formed by treating phosphates with sulfuric acid, and thus was the first to create the artificial manure industry. In the succeeding year he enlisted the services of Joseph Henry Gilbert; together they performed crop experiments at the Institute of Arable Crops Research.[11]

The development of synthetic nitrogen fertilizer has significantly supported global population growth. It has been estimated that almost half the people on the Earth are currently fed as a result of synthetic nitrogen fertilizer use.[19] The use of phosphate fertilizers has also increased from 9 million tonnes per year in 1960 to 40 million tonnes per year in 2000.

Fertilizers enhance the growth of plants. This goal is met in two ways, the traditional one being additives that provide nutrients. The second mode by which some fertilizers act is to enhance the effectiveness of the soil by modifying its water retention and aeration. This article, like many on fertilizers, emphasizes the nutritional aspect.Fertilizers typically provide, in varying proportions:[24]

Fertilizers are classified in several ways. They are classified according to whether they provide a single nutrient (e.g., K, P, or N), in which case they are classified as "straight fertilizers". "Multinutrient fertilizers" (or "complex fertilizers") provide two or more nutrients, for example N and P. Fertilizers are also sometimes classified as inorganic (the topic of most of this article) versus organic. Inorganic fertilizers exclude carbon-containing materials except ureas. Organic fertilizers are usually (recycled) plant- or animal-derived matter. Inorganic are sometimes called synthetic fertilizers since various chemical treatments are required for their manufacture.[27]

NPK fertilizers are three-component fertilizers providing nitrogen, phosphorus, and potassium. There exist two types of NPK fertilizers: compound and blends. Compound NPK fertilizers contain chemically bound ingredients, while blended NPK fertilizers are physical mixtures of single nutrient components.

NPK rating is a rating system describing the amount of nitrogen, phosphorus, and potassium in a fertilizer. NPK ratings consist of three numbers separated by dashes (e.g., 10-10-10 or 16-4-8) describing the chemical content of fertilizers.[29][30] The first number represents the percentage of nitrogen in the product; the second number, P2O5; the third, K2O. Fertilizers do not actually contain P2O5 or K2O, but the system is a conventional shorthand for the amount of the phosphorus (P) or potassium (K) in a fertilizer. A 50-pound (23 kg) bag of fertilizer labeled 16-4-8 contains 8 lb (3.6 kg) of nitrogen (16% of the 50 pounds), an amount of phosphorus equivalent to that in 2 pounds of P2O5 (4% of 50 pounds), and 4 pounds of K2O (8% of 50 pounds). Most fertilizers are labeled according to this N-P-K convention, although Australian convention, following an N-P-K-S system, adds a fourth number for sulfur, and uses elemental values for all values including P and K.[31]

Micronutrients are consumed in smaller quantities and are present in plant tissue on the order of parts-per-million (ppm), ranging from 0.15 to 400 ppm or less than 0.04% dry matter.[32][33] These elements are often required for enzymes essential to the plant's metabolism. Because these elements enable catalysts (enzymes), their impact far exceeds their weight%age. Typical micronutrients are boron, zinc, molybdenum, iron, and manganese.[24] These elements are provided as water-soluble salts. Iron presents special problems because it converts to insoluble (bio-unavailable) compounds at moderate soil pH and phosphate concentrations. For this reason, iron is often administered as a chelate complex, e.g., the EDTA or EDDHA derivatives. The micronutrient needs depend on the plant and the environment. For example, sugar beets appear to require boron, and legumes require cobalt,[1] while environmental conditions such as heat or drought make boron less available for plants.[34]

The production of synthetic, or inorganic, fertilizers requires prepared chemicals, whereas organic fertilizers are derived from the organic processes of plants and animals in biological processes using biochemicals.

Deposits of sodium nitrate (NaNO3) (Chilean saltpeter) are also found in the Atacama desert in Chile and was one of the original (1830) nitrogen-rich fertilizers used.[35] It is still mined for fertilizer.[36] Nitrates are also produced from ammonia by the Ostwald process.

Phosphate fertilizers are obtained by extraction from phosphate rock, which contains two principal phosphorus-containing minerals, fluorapatite Ca5(PO4)3F (CFA) and hydroxyapatite Ca5(PO4)3OH. Billions of kg of phosphate rock are mined annually, but the size and quality of the remaining ore is decreasing. These minerals are converted into water-soluble phosphate salts by treatment with acids.[37] The large production of sulfuric acid is primarily motivated by this application.[38] In the nitrophosphate process or Odda process (invented in 1927), phosphate rock with up to a 20% phosphorus (P) content is dissolved with nitric acid (HNO3) to produce a mixture of phosphoric acid (H3PO4) and calcium nitrate (Ca(NO3)2). This mixture can be combined with a potassium fertilizer to produce a compound fertilizer with the three macronutrients N, P and K in easily dissolved form.[39]

Potash is a mixture of potassium minerals used to make potassium (chemical symbol: K) fertilizers. Potash is soluble in water, so the main effort in producing this nutrient from the ore involves some purification steps; e.g., to remove sodium chloride (NaCl) (common salt). Sometimes potash is referred to as K2O, as a matter of convenience to those describing the potassium content. In fact, potash fertilizers are usually potassium chloride, potassium sulfate, potassium carbonate, or potassium nitrate.[40]

China has become the largest producer and consumer of nitrogen fertilizers[45] while Africa has little reliance on nitrogen fertilizers.[46] Agricultural and chemical minerals are very important in industrial use of fertilizers, which is valued at approximately $200 billion.[47] Nitrogen has a significant impact in the global mineral use, followed by potash and phosphate. The production of nitrogen has drastically increased since the 1960s. Phosphate and potash have increased in price since the 1960s, which is larger than the consumer price index.[47] Potash is produced in Canada, Russia and Belarus, together making up over half of the world production.[47] Potash production in Canada rose in 2017 and 2018 by 18.6%.[48] Conservative estimates report 30 to 50% of crop yields are attributed to natural or synthetic commercial fertilizers.[40][49] Fertilizer consumption has surpassed the amount of farmland in the United States.[47]

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