1.
Melting point
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The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium, the melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the change from liquid to solid. Because of the ability of some substances to supercool, the point is not considered as a characteristic property of a substance. For most substances, melting and freezing points are approximately equal, for example, the melting point and freezing point of mercury is 234.32 kelvins. However, certain substances possess differing solid-liquid transition temperatures, for example, agar melts at 85 °C and solidifies from 31 °C to 40 °C, such direction dependence is known as hysteresis. The melting point of ice at 1 atmosphere of pressure is close to 0 °C. In the presence of nucleating substances the freezing point of water is the same as the melting point, the chemical element with the highest melting point is tungsten, at 3687 K, this property makes tungsten excellent for use as filaments in light bulbs. Many laboratory techniques exist for the determination of melting points, a Kofler bench is a metal strip with a temperature gradient. Any substance can be placed on a section of the strip revealing its thermal behaviour at the temperature at that point, differential scanning calorimetry gives information on melting point together with its enthalpy of fusion. A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window, the several grains of a solid are placed in a thin glass tube and partially immersed in the oil bath. The oil bath is heated and with the aid of the melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, the measurement can also be made continuously with an operating process. For instance, oil refineries measure the point of diesel fuel online, meaning that the sample is taken from the process. This allows for more frequent measurements as the sample does not have to be manually collected, for refractory materials the extremely high melting point may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer. For the highest melting materials, this may require extrapolation by several hundred degrees, the spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source that has been previously calibrated as a function of temperature, in this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer, for temperatures above the calibration range of the source, an extrapolation technique must be employed
2.
Agent Orange
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Agent Orange is a herbicide and defoliant chemical. It is widely known for its use by the U. S. military as part of its herbicidal warfare program, Operation Ranch Hand and it was a mixture of equal parts of two herbicides,2,4, 5-T and 2, 4-D. The chemical damaged the health of people who came into contact with it as well as extensively contaminated the environment, the defoliant caused grievous health consequences for those who came in contact. Up to 4 million people in Vietnam were affected and 1 million people have illnesses, the chemical has damaged the genes, giving descendants with deformities. The US government has documented cases of leukemia, Hodgkins lymphoma as well as various kinds of cancer in veterans. Agent Orange caused enormous damage in Vietnam. Over 3,100,000 hectares of forest were defoliated, defoliants eroded tree cover and seedling forest stock, making reforestation difficult in numerous areas. Animal species diversity sharply reduced in contrast with unsprayed areas, the aftermath of the use of Agent Orange in Vietnam resulted in massive legal consequences. The United Nations ratified Resolution 31/72 and the Environmental Modification Convention, lawsuits filed on behalf of veterans as well as Vietnamese veterans sought compensation for damages. Agent Orange was to a lesser extent used outside Vietnam, some countries saw testing, while other countries such as Canada and Brazil used the herbicide to clear out sections of land for agriculture. Land in Laos and Cambodia was sprayed with Agent Orange because forests on the border with Vietnam were used by the Vietcong, the dioxin TCDD is significant contaminant of Agent Orange. TCDD is the most toxic of the dioxins, and is classified as a carcinogen by the US Environmental Protection Agency. Agent Orange dries quickly after spraying and breaks down within hours to days when exposed to sunlight and is no longer harmful, due to its fat-soluble nature, dioxin enters through physical contact or ingestion. Dioxin easily accumulates in the food chain, Dioxin enters the body by attaching to a protein called the aryl hydrocarbon receptor, a transcription factor. When dioxin binds to AhR, the moves to the nucleus. Several herbicides were discovered as part of efforts by the USA and these included 2, 4-D,2,4, 5-T, MCPA, and isopropyl phenylcarbamate. He discovered both that 2,3, 5-triiodobenzoic acid would speed up the flowering of soybeans and that in higher concentrations it would defoliate the soybeans, from these studies arose the concept of using aerial applications of herbicides to destroy enemy crops to disrupt their food supply. In early 1945, the U. S. Army ran tests of various 2, 4-D and 2,4, 5-T mixtures at the Bushnell Army Airfield in Florida
3.
Malayan Emergency
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Malayan Emergency was the colonial governments term for the conflict. The MNLA termed it the Anti-British National Liberation War, the rubber plantations and tin-mining industries had pushed for the use of the term emergency since their losses would not have been covered by Lloyds insurers if it had been termed a war. Despite the communists defeat in 1960, communist leader Chin Peng renewed the insurgency against the Malaysian government in 1967 and he fled to exile in Thailand, where he lived until his death on 16 September 2013. The Malayan economy relied on the export of tin and rubber, when the British took control of the Malayan economy, they imposed taxes on some Malayan goods, affecting their traditional industries. This led to an increase in poverty for the Malayan people, many Chinese people found employment in tin mines or fields responsible for the trade of materials. This heightened inter-ethnic tensions as the Malay people found that ethnic Chinese had replaced them in certain jobs and this forced many Malays into the rubber industry, which in turn was heavily dependent upon volatile world prices. Economic tension intensified during the Second World War. The Japanese occupation of Malaya began in 1941 and from that point onwards the “export of primary products was limited to the small amounts required for the Japanese economy. ”This led to large areas of rubber plantations being abandoned. The latter was progressively affected by a shortage of parts for machines. Rice imports, which made up a portion of the Malayan diet, fell rapidly due to limited trade. Many people believed that the British would soon return and ‘save’ them so they did not attempt to learn the skills that would be essential for survival. This then led to famine in Malaya from 1942. The withdrawal of Japan at the end of World War II left the British Malayan economy disrupted, problems included unemployment, low wages, and high levels of food inflation, well above the healthy rate of 2–3%. The Malayan Communist Party began to use the failing economy as a tool of propaganda against the British, the British had not addressed the underlying economic problems that were now worse within Malaya than they had ever been. There was considerable labour unrest and a number of strikes occurred between 1946 and 1948. One example of this was a 24-hour general strike organised by the MCP on 29 January 1946, during this time, the British administration was attempting to organise Malayas economy, as revenue from Malayas tin and rubber industries was important to Britains own post-war recovery. Protesters were dealt with harshly, by measures including arrests and deportations, in turn, protesters became increasingly militant. In 1947, alone, the communists in Malaya organised a further 300 strikes, on 16 June 1948, the first overt act of the war took place when three European plantation managers were killed at Sungai Siput, Perak
4.
United States Department of Agriculture
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Approximately 80% of USDAs $140 billion budget goes to the Food and Nutrition Service program. The largest component of the FNS budget is the Supplemental Nutrition Assistance Program, after the resignation of Thomas Vilsack on January 13,2017 and the departure of President Barack Obama from office on January 20,2017, the acting Secretary of Agriculture is Michael Young. Activities in this include the Supplemental Nutrition Assistance Program, which provides healthy food to over 40 million low-income. The USDA also is concerned with assisting farmers and food producers with the sale of crops and it plays a role in overseas aid programs by providing surplus foods to developing countries. This aid can go through USAID, foreign governments, international bodies such as World Food Program, the Agricultural Act of 1949, section 416 and Agricultural Trade Development and Assistance Act of 1954, also known as Food for Peace, provides the legal basis of such actions. The USDA is a partner of the World Cocoa Foundation, early in its history, the economy of the United States was largely agrarian. Officials in the government had long sought new and improved varieties of seeds, plants. In 1837 Henry Leavitt Ellsworth, a Yale-educated attorney interested in improving agriculture, became Commissioner of Patents and he began collecting and distributing new varieties of seeds and plants through members of the Congress and agricultural societies. In 1839, Congress established the Agricultural Division within the Patent Office and allotted $1,000 for the collection of agricultural statistics, Ellsworth was called the Father of the Department of Agriculture. In 1849, the Patent Office was transferred to the newly created Department of the Interior, in the ensuing years, agitation for a separate bureau of agriculture within the department or a separate department devoted to agriculture kept recurring. Lincoln called it the peoples department, in the 1880s, varied advocacy groups were lobbying for Cabinet representation. Business interests sought a Department of Commerce and Industry, and farmers tried to raise the Department of Agriculture to Cabinet rank, finally, on February 9,1889, President Grover Cleveland signed a bill into law elevating the Department of Agriculture to Cabinet level. In 1887, the Hatch Act provided for the funding of agricultural experiment stations in each state. The Smith-Lever Act of 1914 then funded cooperative extension services in each state to teach agriculture, home economics, with these and similar provisions, the USDA reached out to every county of every state. During the Great Depression, farming remained a way of life for millions of Americans. The Department of Agricultures Bureau of Home Economics, established in 1923, published shopping advice and recipes to stretch family budgets and make food go farther. USDA helped ensure that continued to be produced and distributed to those who needed it, assisted with loans for small landowners. The Department of Agriculture was authorized a budget for Fiscal Year 2015 of $139.7 billion, the Washington Post reports that he said There are days when I have literally nothing to do, he recalled thinking as he weighed his decision to quit
5.
United States Environmental Protection Agency
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The EPA was proposed by President Richard Nixon and began operation on December 2,1970, after Nixon signed an executive order. The order establishing the EPA was ratified by committee hearings in the House, the agency is led by its Administrator, who is appointed by the president and approved by Congress. The current administrator is Scott Pruitt, the EPA is not a Cabinet department, but the administrator is normally given cabinet rank. The EPA has its headquarters in Washington, D. C. regional offices for each of the ten regions. The agency conducts environmental assessment, research, and education and it has the responsibility of maintaining and enforcing national standards under a variety of environmental laws, in consultation with state, tribal, and local governments. It delegates some permitting, monitoring, and enforcement responsibility to U. S. states, EPA enforcement powers include fines, sanctions, and other measures. The agency also works with industries and all levels of government in a variety of voluntary pollution prevention programs. In 2016, the agency had 15,376 full-time employees, more than half of EPAs employees are engineers, scientists, and environmental protection specialists, other employees include legal, public affairs, financial, and information technologists. Beginning in the late 1950s and through the 1960s, Congress reacted to increasing concern about the impact that human activity could have on the environment. Senator James E. Murray introduced a bill, the Resources and Conservation Act of 1959, the 1962 publication of Silent Spring by Rachel Carson alerted the public about the detrimental effects on the environment of the indiscriminate use of pesticides. In the years following, similar bills were introduced and hearings were held to discuss the state of the environment, in the colloquium, some members of Congress expressed a continuing concern over federal agency actions affecting the environment. The National Environmental Policy Act of 1969 was modeled on RCA, President Nixon signed NEPA into law on January 1,1970. The law created the Council on Environmental Quality in the Executive Office of the President, NEPA required that a detailed statement of environmental impacts be prepared for all major federal actions significantly affecting the environment. The detailed statement would ultimately be referred to as an impact statement. On July 9,1970, Nixon proposed a reorganization that consolidated many environmental responsibilities of the federal government under one agency. After conducting hearings during that summer, the House and Senate approved the proposal, the agency’s first administrator, William Ruckelshaus, took the oath of office on December 4,1970. In May 2013, Congress renamed the EPA headquarters as the William Jefferson Clinton Federal Building, the EPA is led by an Administrator of the Environmental Protection Agency. As of 2017 Scott Pruitt is the 14th administrator, each EPA regional office is responsible within its states for implementing the Agencys programs, except those programs that have been specifically delegated to states
6.
Pest control
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Pest control refers to the regulation or management of a species defined as a pest, and can be perceived to be detrimental to a persons health, the ecology or the economy. A practitioner of pest control is called an exterminator, Pest control is at least as old as agriculture, as there has always been a need to keep crops free from pests. In order to maximize production, it is advantageous to protect crops from competing species of plants. Techniques such as rotation, companion planting, and the selective breeding of pest-resistant cultivars have a long history. In the UK, following concern about animal welfare, humane pest control, for instance, with the urban red fox which territorial behaviour is used against the animal, usually in conjunction with non-injurious chemical repellents. In rural areas of Britain, the use of firearms for pest control is quite common, chemical pesticides date back 4,500 years, when the Sumerians used sulfur compounds as insecticides. The Rig Veda, which is about 4,000 years old, in the 20th century, the discovery of several synthetic insecticides, such as DDT, and herbicides boosted this development. Many pests have only become a problem as a result of the actions by humans. Modifying these actions can often reduce the pest problem. In the United States, raccoons caused a nuisance by tearing open refuse sacks, many householders introduced bins with locking lids, which deterred the raccoons from visiting. House flies tend to accumulate wherever there is activity and live in close association with people all over the world especially where food or food waste is exposed. Similarly, seagulls have become pests at many seaside resorts, tourists would often feed the birds with scraps of fish and chips, and before long, the birds would rely on this food source and act aggressively towards humans. Living organisms evolve and increase their resistance to biological, chemical, physical or any form of control. Perhaps as far ago as 3000BC in Egypt, cats were being used to control pests of grain such as rodents. In 1939/40 a survey discovered that cats could keep a population of rats down to a low level. However, if the rats were cleared by trapping or poisoning, ferrets were domesticated at least by 500 AD in Europe, being used as mousers. Mongooses have been introduced into homes to control rodents and snakes, biological pest control is the control of one through the control and management of natural predators and parasites. For example, mosquitoes are often controlled by putting Bt Bacillus thuringiensis ssp. israelensis, the treatment has no known negative consequences on the remaining ecology and is safe for humans to drink
7.
Vietnam War
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It was the second of the Indochina Wars and was officially fought between North Vietnam and the government of South Vietnam. The war is considered a Cold War-era proxy war. As the war continued, the actions of the Viet Cong decreased as the role. U. S. and South Vietnamese forces relied on air superiority and overwhelming firepower to conduct search and destroy operations, involving ground forces, artillery, in the course of the war, the U. S. conducted a large-scale strategic bombing campaign against North Vietnam. The North Vietnamese government and the Viet Cong were fighting to reunify Vietnam and they viewed the conflict as a colonial war and a continuation of the First Indochina War against forces from France and later on the United States. The U. S. government viewed its involvement in the war as a way to prevent a communist takeover of South Vietnam and this was part the domino theory of a wider containment policy, with the stated aim of stopping the spread of communism. Beginning in 1950, American military advisors arrived in what was then French Indochina, U. S. involvement escalated in the early 1960s, with troop levels tripling in 1961 and again in 1962. Regular U. S. combat units were deployed beginning in 1965, despite the Paris Peace Accord, which was signed by all parties in January 1973, the fighting continued. In the U. S. and the Western world, a large anti-Vietnam War movement developed as part of a larger counterculture, the war changed the dynamics between the Eastern and Western Blocs, and altered North–South relations. Direct U. S. military involvement ended on 15 August 1973, the capture of Saigon by the North Vietnamese Army in April 1975 marked the end of the war, and North and South Vietnam were reunified the following year. The war exacted a huge human cost in terms of fatalities, estimates of the number of Vietnamese soldiers and civilians killed vary from 966,000 to 3.8 million. Some 240, 000–300,000 Cambodians,20, 000–62,000 Laotians, and 58,220 U. S. service members died in the conflict. Various names have applied to the conflict. Vietnam War is the most commonly used name in English and it has also been called the Second Indochina War and the Vietnam Conflict. As there have been several conflicts in Indochina, this conflict is known by the names of its primary protagonists to distinguish it from others. In Vietnamese, the war is known as Kháng chiến chống Mỹ. It is also called Chiến tranh Việt Nam, France began its conquest of Indochina in the late 1850s, and completed pacification by 1893. The 1884 Treaty of Huế formed the basis for French colonial rule in Vietnam for the seven decades
8.
Jmol
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Jmol is computer software for molecular modelling chemical structures in 3-dimensions. Jmol returns a 3D representation of a molecule that may be used as a teaching tool and it is written in the programming language Java, so it can run on the operating systems Windows, macOS, Linux, and Unix, if Java is installed. It is free and open-source software released under a GNU Lesser General Public License version 2.0, a standalone application and a software development kit exist that can be integrated into other Java applications, such as Bioclipse and Taverna. A popular feature is an applet that can be integrated into web pages to display molecules in a variety of ways, for example, molecules can be displayed as ball-and-stick models, space-filling models, ribbon diagrams, etc. Jmol supports a range of chemical file formats, including Protein Data Bank, Crystallographic Information File, MDL Molfile. There is also a JavaScript-only version, JSmol, that can be used on computers with no Java, the Jmol applet, among other abilities, offers an alternative to the Chime plug-in, which is no longer under active development. While Jmol has many features that Chime lacks, it does not claim to reproduce all Chime functions, most notably, Chime requires plug-in installation and Internet Explorer 6.0 or Firefox 2.0 on Microsoft Windows, or Netscape Communicator 4.8 on Mac OS9. Jmol requires Java installation and operates on a variety of platforms. For example, Jmol is fully functional in Mozilla Firefox, Internet Explorer, Opera, Google Chrome, fast and Scriptable Molecular Graphics in Web Browsers without Java3D
9.
Auxin
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Auxins are a class of plant hormones with some morphogen-like characteristics. Auxins have a role in coordination of many growth and behavioral processes in the plants life cycle and are essential for plant body development. Auxins and their role in plant growth were first described by the Dutch scientist Frits Warmolt Went, Kenneth V. Thimann was the first to isolate one of these phytohormones and determine its chemical structure as indole-3-acetic acid. Went and Thimann co-authored a book on plant hormones, Phytohormones, Auxins were the first of the major plant hormones to be discovered. They derive their name from the Greek word αυξειν, auxin is present in all parts of a plant, although in very different concentrations. The concentration in each position is crucial information, so it is subject to tight regulation through both metabolism and transport. The pattern of auxin distribution within the plant is a key factor for plant growth, its reaction to its environment and it is achieved through very complex and well coordinated active transport of auxin molecules from cell to cell throughout the plant body — by the so-called polar auxin transport. Thus, a plant can react to external conditions and adjust to them, Auxins typically act in concert with, or in opposition to, other plant hormones. For example, the ratio of auxin to cytokinin in certain plant tissues determines initiation of root versus shoot buds, on the molecular level, all auxins are compounds with an aromatic ring and a carboxylic acid group. The most important member of the family is indole-3-acetic acid, which generates the majority of auxin effects in intact plants. However, molecules of IAA are chemically labile in aqueous solution, five naturally occurring auxins in plants include indole-3-acetic acid, 4-chloroindole-3-acetic acid, phenylacetic acid, indole-3-butyric acid, and indole-3-propionic acid. Alongside endogenous auxins, scientists and manufacturers have developed many synthetic compounds with auxinic activity, synthetic auxin analogs include 1-naphthaleneacetic acid,2, 4-dichlorophenoxyacetic acid, and many others. Some synthetic auxins, such as 2, 4-D and 2,4, broad-leaf plants, such as dandelions, are much more susceptible to auxins than narrow-leaf plants such as grasses and cereal crops, so these synthetic auxins are valuable as synthetic herbicides. In 1881, Charles Darwin and his son Francis performed experiments on coleoptiles, the experiment exposed the coleoptile to light from a unidirectional source, and observed that they bend towards the light. By covering various parts of the coleoptiles with an opaque cap, the Darwins discovered that light is detected by the coleoptile tip. However the seedlings showed no signs of development towards light if the tip was covered with an opaque cap, in 1913, Danish scientist Peter Boysen-Jensen demonstrated that the signal was not transfixed but mobile. He separated the tip from the remainder of the coleoptile by a cube of gelatine which prevented cellular contact, the seedlings responded normally bending towards the light. However, when the tip was separated by an impermeable substance, in 1928, the Dutch botanist Frits Warmolt Went showed that a chemical messenger diffuses from coleoptile tips
10.
Vapor pressure
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Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system. The equilibrium vapor pressure is an indication of a liquids evaporation rate and it relates to the tendency of particles to escape from the liquid. A substance with a vapor pressure at normal temperatures is often referred to as volatile. The pressure exhibited by vapor present above a surface is known as vapor pressure. As the temperature of a liquid increases, the energy of its molecules also increases. As the kinetic energy of the molecules increases, the number of molecules transitioning into a vapor also increases, the vapor pressure of any substance increases non-linearly with temperature according to the Clausius–Clapeyron relation. The atmospheric pressure boiling point of a liquid is the temperature at which the pressure equals the ambient atmospheric pressure. With any incremental increase in temperature, the vapor pressure becomes sufficient to overcome atmospheric pressure. Bubble formation deeper in the liquid requires a pressure, and therefore higher temperature. More important at shallow depths, is the temperature required to start bubble formation. The surface tension of the wall lead to an overpressure in the very small initial bubbles. Thus, thermometer calibration should not rely on the temperature in boiling water, the vapor pressure that a single component in a mixture contributes to the total pressure in the system is called partial pressure. Vapor pressure is measured in the units of pressure. The International System of Units recognizes pressure as a unit with the dimension of force per area. One pascal is one newton per square meter, experimental measurement of vapor pressure is a simple procedure for common pressures between 1 and 200 kPa. Most accurate results are obtained near the point of substances. Better accuracy is achieved when care is taken to ensure that the entire substance and this is often done, as with the use of an isoteniscope, by submerging the containment area in a liquid bath. Very low vapor pressures of solids can be measured using the Knudsen effusion cell method, the Antoine equation is a mathematical expression of the relation between the vapor pressure and the temperature of pure liquid or solid substances
11.
2,4-Dichlorophenoxyacetic acid
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2, 4-Dichlorophenoxyacetic acid is an organic compound with the chemical formula C8H6Cl2O3. It can be found in commercial lawn herbicide mixtures, and is widely used as a weedkiller on cereal crops, pastures. Over 1,500 herbicide products contain 2, 4-D as an active ingredient,2, 4-D is a possible carcinogen per WHO. Some ester forms are highly toxic to fish and other aquatic life,2, 4-D was one of the ingredients in Agent Orange, a herbicide widely used during the Vietnam War. However, another ingredient in Agent Orange,2,4, 5-T,2, 4-D is primarily used as a selective herbicide which kills many terrestrial and aquatic broadleaf weeds, but not grasses. It acts by mimicking the action of the plant growth hormone auxin, because it was discovered in the 1940s, there is no longer a patent governing the manufacture and sale of 2, 4-D, and any company is free to produce it. Thus, it is sold in formulations under a wide variety of brand names. 2, 4-D can be found in commercial lawn herbicide mixtures, over 1,500 herbicide products contain 2, 4-D as an active ingredient. A wide variety of different sectors use products containing 2, 4-D to kill weeds, in agriculture, it was the first herbicide found to be capable of selectively killing weeds but not crops. It has been used since 1945 to control broad-leafed weeds in pastures, orchards, cereals, in particular, have excellent tolerance to 2, 4-D when it is applied before planting. 2, 4-D is the cheapest way for farmers to control winter annual weeds by spraying in the fall and this is particularly effective before planting beans, peas, lentils and chickpeas. In domestic lawn and garden maintenance,2, 4-D is commonly used for weed control in lawns and it is used to kill unwanted weeds such as dandelions, plantain, clover and chickweed. In forestry, it is used for treatment, trunk injection. Along roadways, railways, and power lines it is used to control weeds and brush which might interfere with safe operation, along waterways it is used to control aquatic weeds that might interfere with boating, fishing and swimming or clog irrigation and hydroelectric equipment. A2010 monitoring study conducted in the US and Canada found that current exposures to 2,2,4 D has been used in laboratories for plant research as a supplement in plant cell culture media such as MS medium since at least 1962. 2, 4-D is used in plant cell cultures as a dedifferentiation hormone and it is classified as an auxin plant hormone derivative. Some scientists are experimenting with soaking tomatoes in 2, 4-D as a way of slowing their ripening after they are harvested. Men who work with 2, 4-D are at risk for abnormally shaped sperm and thus fertility problems, according to the U. S. Environmental Protection Agency, The toxicity of 2, 4-D depends on its chemical forms, including salts, esters, and an acid form
12.
Herbicide
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Herbicide, also commonly known as weedkillers, are chemical substances used to control unwanted plants. Apart from selective/non-selective, other important distinctions include persistence, means of uptake, Herbicides have also been used in warfare and conflict. Modern herbicides are often mimics of natural plant hormones which interfere with growth of the target plants. The term organic herbicide has come to mean herbicides intended for organic farming, due to herbicide resistance - a major concern in agriculture - a number of products also combine herbicides with different means of action. In the US in 2007, about 83% of all herbicide usage, in 2007, world pesticide expenditures totaled about $39.4 billion, herbicides were about 40% of those sales and constituted the biggest portion, followed by insecticides, fungicides, and other types. Smaller quantities are used in forestry, pasture systems, and management of areas set aside as wildlife habitat, prior to the widespread use of chemical herbicides, cultural controls, such as altering soil pH, salinity, or fertility levels, were used to control weeds. Mechanical control was used to control weeds. The first modern herbicide,2, 4-D, was first discovered and synthesized by W. G. Templeman at Imperial Chemical Industries, in 1940, he showed that Growth substances applied appropriately would kill certain broad-leaved weeds in cereals without harming the crops. By 1941, his team succeeded in synthesizing the chemical, in the same year, Pokorny in the US achieved this as well. Independently, a team under Juda Hirsch Quastel, working at the Rothamsted Experimental Station made the same discovery, Quastel was tasked by the Agricultural Research Council to discover methods for improving crop yield. By analyzing soil as a system, rather than an inert substance. Quastel was able to quantify the influence of plant hormones, inhibitors and other chemicals on the activity of microorganisms in the soil. While the full work of the unit remained secret, certain discoveries were developed for use after the war, including the 2. When it was released in 1946, it triggered a worldwide revolution in agricultural output. It allowed for greatly enhanced weed control in wheat, maize, rice, and similar cereal crops, because it kills dicots. The low cost of 2, 4-D has led to continued usage today, like other acid herbicides, current formulations use either an amine salt or one of many esters of the parent compound. These are easier to handle than the acid, atrazine does not break down readily after being applied to soils of above neutral pH. Under alkaline soil conditions, atrazine may be carried into the profile as far as the water table by soil water following rainfall causing the aforementioned contamination
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