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Part 2 - Fertilizers

In 1701 Jethro Tull's seed drill mechanized seeding by placing seeds at the correct depth and spacing but the first drills were fragile, expensive and unreliable and were not widely used until the late 19th century when manufacturing techniques improved. Many early drills, which could be pulled by a single horse, remained in use into the 1930s. The use of steam engines and diesel powered tractors and larger drills allowed farmers to plant seed over large areas in a single day.

In 1807, William Cubitt patented windmill sails with connected shutters to improve the productivity and, in the twentieth century, the science of aerodynamics led to further improvements and the development of modern, power generating windmills.

In the mid 18th century, Robert Bakewell and Thomas Coke used selective breeding to improve desirable traits in animals such as the New Leicester sheep while others selectively bred heavy horses, for plowing and cartage, like the Clydesdale and Percheron.

Andrew Meikle's threshing machine of 1784 improved farming productivity while better plows were invented between 1730 and 1776 by Joseph Foljambe and many others. 

In 1789 Ransomes, Sims & Jefferies was producing 86 plow models for different soils. These were improved by James Small and Jethro Wood, of Scipio, New York, who made a plow with three parts so that a broken piece could be replaced. 

Richard Trevithick's stationary steam engine was used to drive a threshing machine in 1812 and mechanization quickly spread to other farms. In 1837 John Deere developed a polished, cast steel plow suitable for use in sticky soil and strong enough to work soil previously considered unsuitable for farming in the USA. The first commercially successful gasoline-powered tractor was built in 1901 by Dan Albone and by 1923 the International Harvester Farmall tractor began to replace draft animals. Since then, self-propelled combined harvesters, planters, transplanters and other machines have revolutionized agriculture permitting farming tasks to be completed on a scale and with a speed previously unimaginable. 

The first artificial pesticide, an arsenic compound, was used to kill Colorado potato beetles. 

Guano, introduced from Peru, was the first use of old deposits of bird excreta as fertilizer in Europe. But these were rapidly exhausted and by 1877 the world desperately needed a new source both for agriculture and gunpowder. 

The modern science of plant nutrition started with the German chemist Justus von Liebig. (Plants need phosphorus, nitrogen and potassium with trace amounts of boron, copper, zinc and other elements in addition to water and sunlight).

In 1842, John Bennet Lawes began a scientific investigation of crop fertilization and founded one of the first fertilizer factories that extracted phosphate from coprolites (fossilized animal faeces) with sulphuric acid. The main source of nitrates (NO3) and ammonia (NH3)for fertilizers was niter (potassium nitrate, KNO3, also known as saltpeter) and atmospheric nitrogen was abundantly available but converting it into ammonia was difficult as nitrogen did not easily react with other chemicals.

The first commercial process was developed in Norway by Kristian Birkeland and Sam Eyde in 1903, based on a process devised by Henry Cavendish in 1784 that fixed atmospheric nitrogen (N2) into nitric acid (HNO3) which was then used as a source of nitrate (NO3). 

Fritz Haber developed a process using catalysts and high-pressure in 1909 and the German chemist Carl Bosch built an industrial plant in 1910. The process produced ammonia (NH3) from methane (CH4) gas and atmospheric molecular nitrogen (N2). The ammonia was then converted into nitric acid (HNO3).Ammonia production from the BASF's plant in Germany reached 20 tonnes per day in 1914 just in time to supply nitrate explosives for the German war effort in World War I.

Haber and Bosch were later awarded Nobel prizes for their work on the production of ammonium nitrate which substantially increased crop yields. (About half of the global population is currently supplied with food grown with synthetic nitrogen fertilizer). Presently the world's farmers use 100 million tonnes of nitrogen each year. 

Synthetic nitrogen fertilizer allowed significant global population growth and about half the people on the Earth are currently fed as a result of synthetic nitrogen fertilizer use.

The use of phosphate fertilizers also increased substantially, to 40 million tonnes per year in 2000. A maize crop yielding between 6 and 9 tonnes of grain per hectare (2.5 acres) requires 31 to 50 kilograms (68–110 lb) of phosphate fertilizer; soybean crops require 20 to 25 kg per hectare.

https://www.youtube.com/watch?v=aaiT5cRO4HI Phosphorus

The number of people employed in the American farming industry fell from 24 % of the population to 1.5 % by 2002. The number of farms also decreased. In 1967 there were one million pig farms in America but by 2002 this had been consolidated into 114,000.

The Green Revolution included a number of research, development, and technology transfers between 1950 and the 1970s that increased agriculture production around the world. Norman Borlaug is credited with saving over a billion people from starvation, when he developed high-yielding varieties of short stemmed cereal grains. Improved infrastructure and irrigation, the use of modern management methods, the distribution of hybridized seeds, synthetic fertilizers, and pesticides, to farmers all contributed to a huge increase in food crops in many less developed countries, often despite intense bureaucratic resistance.

https://www.youtube.com/watch?v=XELGBB-jqNQ Mining potash