Chemical raw materials in agriculture
Chemicals in agriculture are fertilizers, liming and acidifying agents (aimed at changing the pH), soil conditioners, pesticides and chemicals used in animal husbandry, such as vitamins, antibiotics and hormones. Agrochemicals are increasingly important for modern farms. As farms have become huge, the challenges of keeping crops free from damage have increased.
Fertilizers are substances added to agricultural land to make up for nutrient deficiencies, enabling a significant increase in crop growth. Over 150 million tonnes of fertilizer have been used in agriculture worldwide since 2006. In the United States, the average fertilization dose is about 100 kilograms per hectare. In total, around 21 million tonnes (19 million metric tons) are consumed annually.
The most commonly used fertilizers are inorganic nitrogen compounds (N). In conditions where agricultural crops have access to sufficient water, their productivity is most often limited by providing available forms of nitrogen, especially nitrate (NO3-) and sometimes ammonium (NH4 +). Farmers usually increase the availability of these inorganic forms of nitrogen by using appropriate fertilizers such as urea or ammonium nitrate. The rate of fertilization in intensive farming systems is usually over a ton of nitrogen per hectare per year.
Phosphorus (P) and potassium (K) are other commonly used nutrients in agriculture. Most phosphate fertilizers are made from stone phosphate and are known as superphosphate and triple superphosphate. Some other phosphorus fertilizers are made from bone meal or guano from seabirds. Potassium fertilizers are mainly produced from extracted potash.
Often, these three macronutrients are used in a combined formulation that contains nitrogen in so-called N-P-K fertilizer. For example, 10-10-10 fertilizer would contain materials such as 10% nitrogen (N), 10% P2O5 (source of phosphorus [P]) and 10% K2O (source of potassium [K]), while 4-8-16 would contain these nutrients at concentrations of 4%, 8% and 16% respectively. The desired proportions of these three nutrients depend on the quality of the fertilized soil and the needs of the specific crop.
For example, sulfur, calcium or magnesium limit the yield of crops in some places. Micronutrients such as copper, molybdenum or zinc should rarely be used for optimal crop growth.
Liming and acidifying agents
Arable lands are usually too acidic or too basic for optimal growth of many crop species. In this case, fertilizers can be added to the soil to adjust its pH to a more appropriate range. Chemical raw materials in agriculture improve soil quality.
Acid soils are a particularly common problem in agriculture. Acid soil can be caused by various factors, e.g. removal of the acid neutralizing principles contained in the biomass of harvested plants, the use of certain types of fertilizers, acid rain, oxidation of sulfide minerals and the presence of certain types of organic substances in the soil. Because soil acidification is such a common phenomenon, neutralizing (or liming) materials are one of the most important agrochemicals used in terms of the amount of soil added each year.
Acid soils are usually neutralized by the addition of calcium-containing minerals, usually calcite (CaCO3) in the form of powdered limestone or crushed oyster shells or clams. Alternatively, the acidity of the soil can be neutralized with faster-acting lime (Ca [OH] 2). The amount of acid neutralizing product used in agriculture can vary considerably, from tonnes per hectare per year to over 3 tonnes per hectare per year. The doses used depend on the acidity of the soil, the speed at which new acidity is generated, and the needs of specific crops.
Soils are less likely to be alkaline and require some acidification to bring them to a pH range suitable for most crops to grow. This problem may be particularly common in soils developed from parent materials with large amounts of limestone (CaCO3) or dolomite (CaMg [CO3] 2). The soil can be acidified by the addition of sulfur compounds, which produce acidity during oxidation, or by the addition of certain types of acidic organic substances, such as peat extracted from peat bogs.
Soil improvers are rich in organic materials that are sometimes added to soils to improve aeration and water retention, which are very important aspects of soil quality. A variety of materials can be used as soil improvement agents, including peat, crop residues, animal manure, sewage sludge, and even shredded newspapers. However, compost is the most desirable soil conditioner. Compost contains large amounts of well-moisturized org.
Division of pesticides
Pesticides are chemically diverse substances. Currently, about 300 different insecticides are used, as well as about 290 herbicides, 165 fungicides and other pesticides. However, any specific pesticidal chemical (also known as “active ingredient”) can be sold in a variety of formulas that contain additional substances that work to increase the effectiveness of the actual pesticide. These so-called “inert” formulation ingredients may include solvents, detergents, emulsifiers and chemicals that allow the active ingredient to adhere better to the leaves. In total, there are over 3000 different pesticide preparations.
Pesticides can also be classified according to the similarity of their chemical structures. For example, inorganic pesticides are simple compounds of toxic elements such as arsenic, copper, lead and mercury. Inorganic pesticides have previously been used in large quantities, especially as fungicides. However, they have been largely replaced by various organic (carbon-containing) pesticides.
Several commonly used organic pesticides are based on substances that are naturally synthesized by plants as biochemical defense agents and can be extracted and used against pests. Pyrethrin is, for example, an insecticide based on pyrethrum, which is obtained from the species chrysanthemum, while rotenone is a rodenticide extracted from a tropical shrub.
However, most organic pesticides have been synthesized by chemists. Synthetic organic pesticides include such well-known groups as chlorinated hydrocarbons (including DDT insecticide and 2, 4-D and 2, 4, 5-T herbicides), organic phosphates (such as parathion and malathion), carbamates (for e.g. carbaryl and carbofuran) and triazine herbicides (such as atrazine and simazine).
The final class of pesticides is based on the action of bacteria, fungi or viruses that are pathogenic to specific pests and can be used as a pesticide formulation. The most commonly used biological insecticide is produced using Bacillus thuringiensis spores, also known as Bt. These spores can be mass-produced in laboratory-like factories and then used to prepare an insecticide solution. Bt-containing insecticides are mainly used against leaf-eating moths, such as flies and mosquitoes. Most other insects have little effect on Bt-based insecticides, so the unintended unintentional effects of their use are relatively small.
Agrochemicals used in animal husbandry
Contagious livestock diseases can be a problem in modern agriculture. This is especially dangerous when animals are bred in large numbers. Under these conditions, various agrochemicals can be used to control infectious diseases and parasites. Antibiotics are particularly important in this regard. These chemicals can be administered by injection whenever bacterial diseases are diagnosed. However, antibiotics are sometimes given with feed as a preventive treatment to prevent infection. Due to the very crowded conditions, when animals are bred on “factory farms”, antibiotics must be given routinely.
Sometimes hormones and other animal growth regulators are used to increase livestock performance. For example, bovine growth hormone is routinely given in some farming systems to increase cow growth rate and milk production. Such use is also disputed; critics say the health’s unclear effect speaks against growth hormone supplementation.
Impact of agrochemicals on the environment
Many important benefits are obtained through the use of agrochemicals. They are largely associated with increased crop yields and animals and less deterioration during storage. These benefits are significant. Combined with genetically improved varieties of agrochemical plant species, they have significantly contributed to the success of the “green revolution”. This helped increase food supply for the rapidly growing population of people on Earth.
However, the use of some agrochemicals also involves some significant damage to the environment and ecology. Excessive use of fertilizers can lead to groundwater pollution by nitrate, rendering them unsuitable for human or farm animal consumption. Water containing a high concentration of nitrates can poison animals, immobilizing some of the hemoglobin in the blood, reducing the ability to transport oxygen. In addition, the flow of agricultural fertilizers into streams, lakes and other surface waters can cause increased efficiency of these aquatic ecosystems, a problem known as eutrophication. The ecological effects of eutrophication may include the high mortality of fish and other aquatic animals, as well as the excessive growth of harmful algae and the unpleasant taste of drinking water.
The use of pesticides can also cause environmental problems. Pesticides in agriculture occur in order to reduce the number of target pest species to a level below the permissible level of damage, which is economically determined. Unfortunately, during many pesticide applications in agriculture, other organisms, including humans, are also exposed. This is particularly acute when entire fields are sprayed, for example from an airplane. Many non-target organisms are exposed to pesticides during this type of spraying.