British Agricultural Revolution
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The British Agricultural Revolution describes a period of agricultural development in Britain between the 15th century and the end of the 19th century, which saw an increase in productivity and net output that broke the historical food scarcity cycles. Every continent in the world has experienced a period of agricultural retardation throughout history. These retardations effectively limited the population which local territories could sustain over long periods of time. Famines when food is unavailable for a period of time, usually exceeding a year, and the resources necessary to sustain large static populations - agricultural workers, money, and transportation - are not available. Since food shortages are usually "local" affairs the ability to buy and transport food over much longer distances helped minimize the impacts of local food shortages.
Lessons from abroad 
The British Agricultural Revolution occurred over a period of several centuries and milleniums(more akin to an evolution than a revolution) and was preceded or closely duplicated by many countries in Europe and their colonies. One of the keys to the British Agricultural Revolution was the development of ways of keeping and improving the arable land in Great Britain to counteract the loss of the soil's plant nutrients in cropping a given area. Higher yielding land was added to higher yielding crops with more yield/acre. Farm workers using more productive tools and machinery produced more crops with fewer workers. The Agricultural Revolution picked up speed as the Industrial Revolution and the advances in chemistry produced the scientific knowledge, wealth and technology for a more systematic development of commercial fertilizers and new and more productive agricultural machinery. New crops like potatoes (introduced about 1600), corn, etc. were introduced from the Americas improving the yield/acre of arable land.
The British agricultural revolution, the British Industrial Revolution and Scientific Revolution developed in lock-step. Without increasing amounts of food to feed the increasing city populations the Industrial and Scientific Revolutions could not have proceeded. Without the capital, tools, metals, increased agricultural markets, scientific and technical knowledge generated by the Industrial and Scientific Revolution the Agricultural Revolution would not have been possible. Each so called "Revolution" supported and advanced the other revolutions—they were (and still are) intricately linked together.
Advances that helped the Agriculture Revolution 
Very few people will want to work harder or smarter if their work or income can arbitrarily be seized by those in power. One of the keys to the British Agricultural Revolution was the traditional restricted role of kings and the aristocracy, as exemplified by a long legal tradition going back to at least the signing of the Magna Carta by King John of England in 1215. The British Agricultural Revolution relied in large part on the establishment of limited government that used Parliament-passed laws, English Common law, the established Courts with Judicial independence and the rule of law to protect life, liberty and property in England, Wales, Scotland, etc. Empowering the farmers, investors, inventors and businessman was accomplished by increasingly and successfully restricting the power of the Pope and the king and the aristocracy in England. King Henry VIII of England separated the Church of England from the often repressive rule of the Pope and the Roman Catholic Church and its many bishops, clerics, Ecclesiastical courts, etc. in 1535. In the English Civil War (1640–1649) the Parliamentarians under Oliver Cromwell (1599–1658) defeated and executed the king, Charles I of England, and abolished about 700 king granted monopolies. After 1660 when King Charles II of England (1630–1685) was restored and then again after 1685 when King James II of England came to power there was an on-going battle between king and the English Parliament. This was resolved in the Parliament's favor in 1688 when the Catholic Stuart King James II of England was forced to flee for his life to France. At the end the Glorious Revolution in 1688, the new king and queen, William and Mary agreed to abolish nearly all remaining monopolies and signed the English Bill of Rights 1689 and eliminated the hearth tax marking a new level co-operation and power sharing between the Parliament and the English monarchs. All of these processes led to a greater measure of legal protection for life, liberty, and property in England that encouraged and empowered the middle class at the beginning of the Agricultural and Industrial Revolutions. The Glorious Revolution of 1688 signalled the lessening of several centuries of tension and conflict between the crown and parliament, and the end of the idea that English kings had any divine rights and that England, etc. would be restored to Roman Catholicism. The new King William III and his wife Mary II were Protestant leaders from the Dutch Republic that were invited by Parliament to rule England. To make up for the loss of tax revenue, due to the cancellation of the hearth tax, uniform property taxes were imposed with few exclusions.
With legal assurances that their property and work would not be arbitrarily confiscated without legal proceedings by the king, the so-called "nobility", church or anybody else investors and inventors could secure capital to invest or use sweat equity to build improved farms or make other improvements. All realized some taxes were necessary to maintain law and order, pay for a government bureaucracy, tax collectors, monarchy, an Army and a Navy, post office system, and protect life, liberty and property by running an independent court system. The government was run with an approximate average tax rate of about 10% of GDP with taxes rising to about 20% of GDP in the Seven Years' War, American Revolutionary War and the Napoleonic Wars and then receding back to about 10% when the war bonds, loans etc. were paid off. Private investors financed and built transportation systems like sailing ships, paddle steamers (after 1830), steam ships (after 1860), refrigerator ships (after 1890), toll roads (after 1700), canals (after 1760), railways (after 1830) allowed people, goods, foods and animal crops to be gathered and shipped cheaply and with increasing rapidity over ever increasing distances. New food preservation techniques like canning (after 1800), refrigeration (after 1880) as well as traditional food storage techniques like root cellars, granaries, etc. were improved. These allowed more food to be stored over longer periods of time and minimized the impact of local shortages.
Ever increasing literacy, spread in large part by the Protestant Reformation and its pressure to read and study the Bible in English, was well spread in England and even broader in Scotland. Public pressure and public and private funding were used to try and teach more and more males and some females to read, write and cipher. The fraction of the populace educated continually increased with about 30% of all males at least semi literate by 1630, rising to 60% by 1730 and 65% by 1830 before reaching 90% in 1900. English women literate rates were about 10% by 1700, 35% by 1800 and increasing to 90+% by 1900. Cheap and wide spread "How-To" books made possible by Johannes Gutenberg's invention of the printing press (1438) and the numerous and wide spread low cost books and other literature that were made available. Increased literacy led to increased (uncensored) printing of books magazines and newspapers to satisfy a growing demand. Information on successful new agricultural techniques, scientific discoveries, inventions, prices and information of surpluses and shortages were spread faster and over much wider territories by the wide availability of cheap (compared to hand copied) books, magazines and newspapers.
New scientific discoveries found by Sir Isaac Newton, Charles Darwin and many others were increasingly added to the school curriculum and studied by an increasingly widening student body. New technologies like the telegraph (after 1830) and the telephone (after 1880) greatly improved the speed and flow of information needed to keep up with prices, shortages and surpluses to know which crops to buy, ship or grow. New crop rotation systems involving turnips and clover (plus others) made it less necessary to have so much land lie fallow. New crops had more yield per acre and new improved livestock that could be fed though the winters gave larger yields of meat. Larger drives of livestock from Ireland, Wales and Scotland increased the available meat supply available to be purchased in the ever increasing cities. New irrigation systems called water meadows allowed longer growing seasons on pasture land and increased yield from hay fields allowing more animals to be raised. Improved use and new fertilizers in addition to "manure" helped maintain and improve the arable land or reclaim formerly "waste" land. These improvements and new crops in turn supported unprecedented population growth, freeing up a significant percentage of the workforce, and thereby helped drive the Industrial Revolution.
The development of more sophisticated financial systems helped farmers acquire more capital (raised from other investors) which they needed to buy farm equipment to improvement the efficiency of their farms. As it is more economical to use as few herders as practicable to herd livestock from Ireland, Wales and Scotland to England for fattening and/or slaughter accumulating the money to buy these herds was much facilitated by a workable banking system. The income earned by the workers in the Industrial Revolution in turn allowed these workers to buy and pay for more agricultural farm and livestock production. The Industrial Revolution also made many things much cheaper so that farmers could purchase more extensive wardrobes, metal tools, new machines, and other goods, with the same quantity of earnings. The much cheaper textile manufacturing brought about by the Industrial Revolution made available cheap washable cotton underwear that improved personal hygiene and slowed down the spread of gastrointestinal diseases like cholera etc.
There were large variations in the location and time different agricultural innovations were introduced in the many different agricultural zones in Britain and the rest of the world. Advances in science, engineering and elementary botany encouraged the progression of the Agricultural Revolution in Britain and elsewhere. More professional farm management, more capital investment, better agricultural education, improved fertilizations, new improved crops or higher yield, mechanization of farm work from oxen, horses, steam power and then gasoline or diesel power, four-field crop rotation, and selective breeding of livestock for larger size and other desirable characteristics have been highlighted as important links to the Agricultural revolution.
Increased understanding of the important chemicals need for proper plant nutrition allowed new fertilizers to be imported and made. Eventually the establishment of a chemical fertilizer industry made it possible to restore the chemicals lost in growing crops to maintain the needed enhanced food plant growth.
New agricultural equipment like cultivators, ploughs, threshers, mowers, combines, balers, etc. were invented and powered by oxen, horses, steam power, then gasoline or diesel as the farm machinery became mechanized and allowed the farmers to become ever more productive. The farm transportation system moved from pack animals to carts and wagons pulled by oxen, to mules or horses to trucks (after about 1915).
As the Industrial Revolution picked up speed in the early 1800s the metal technologies, power sources, metal working skills, monetary systems, investors, capital, etc. became available for agricultural continuation and improvement. Early successes led to ever increasing innovative agricultural machinery and labor saving devices. The percentage of the population in agricultural work decreased from about 80% in the 1300s to less than 2% today (in the developed world) as the agricultural "revolution" continues.
Farm life in the 15th to 18th century 
The about 77,800,000 acres (about 31,480,000 hectares) of land in Britain pre-1922 varied considerably in arability. England had about 30% arable land with Wales, Scotland and Ireland favoring raising livestock and dairy farming with only about 3%, 7% and 15% arable land respectively. Nearly all of Britain is less than 75 miles (121 km) from the ocean and many communities have close ties to fishing and trade. Nearly all farmers kept livestock as well as growing crops on arable land for their own food and a small extra amount to trade with the towns people for goods they couldn't or didn't have time to make. The livestock were almost a necessity as they could eat pasture during the day and spread some of their manure over arable or fallow land during the night if a crop was not planted there yet. During the winter when they were fed and housed their manure built up around the stock pens and was usually hauled out in the spring and spread on the grain fields before they were ploughed. To help keep the land productive manure or other plant matter had to be spread on the soil by the livestock or the farmer regularly to maintain the plant nutrient levels needed to grow wheat, oats, rye, barley, etc. Barley was grown primarily to be brewed into beer, but it was also eaten, usually in dish called "pottage". The water in this time period (before germs were known or water treatment plants) was so unsafe that beer was a very common beverage drunk by nearly all—children included. Oats, rye and wheat were primarily used in cereals and breads, but these grains were also used in pottage (this staple dish for the poor also included seasonal vegetables and could include pulses and bits of meat). The productivity of the farms gradually increased as a larger fraction moving to the cities left fewer farmers to grow more and larger crops.
Nearly all farm and village families kept gardens that grew a wide variety of vegetables that were used when they had ripened or grown large enough. Nearly all farmers kept pigs, which could often scrounge most of their own food or eat milk left over from making cheese, scraps or slop, and were fattened on acorns in autumn before slaughter. Most kept chickens, which could provide eggs and meat and which could often scrounge much of their food in the summer and only needed to be fed during the winter months. Cows were kept by most farmers for their hides, milk, meat and manure as well as being used as draft animals. Sheep were kept for their hides, milk, meat, manure as well as their wool. Wool was a "money" crop that allowed the wool to be sold for extra money to buy the few things that weren't produced on the farm. Some wool was often kept to be spun by women on a spinning wheel into thread and then put on a loom to be woven into cloth. Making cloth and clothing was so labour-intensive (before the Industrial Revolution) that many farmers only had two to three different sets of clothing per lifetime. The most sheep were usually owned by the largest land owners. Initially horses were scarce, owned only by large land owners, as they required more winter feed and were only slightly more productive as farm animals than oxen, which could live on poorer food and be eaten. A horse was seldom eaten by people in Britain.
The main disadvantage of farm animals is that food had to be provided for them during the winters. The winters in Middle age society were always a time of stress where you, your family and your animals had to try and survive on whatever food could be saved through a non growing season. The herds were nearly always cut down by killing or selling many of the livestock and pigeons, chickens, geese, pigs, etc. The meat was salted and stored in barrels to try and preserve it through the winters and the leather used to make many of the items needed on a farm. Dried grains used for cereals, breads, and pottage, salted meat and fish, and seasonal vegetables such as onions, leeks, and cabbage were the most common food items in the winter. Fresh milk and cheese were seldom eaten as the cows were "dried up" to help them get through the winter on poor feed. Often by spring nearly everyone was on restricted rations of a very monotonous diet. Early garden vegetables were considered a great treat. A bad storm or lack of rain at the right time could seriously reduce the crops needed for the winter and there was only a limited recourse because of the limited money, time, and transportation facilities. Farmers seldom kept significant grain reserves above that needed for next year's seeds.
Soil maintenance 
To grow more food the land has to be maintained at its present nutrient level or better so it can grow larger and better crops. Each crop removes some essential nutrients (N:P:K+) from the soil. One of the keys to the Agricultural Revolution was the use of manure and bacteria in symbiosis with legume roots, which could be used to fix nitrogen (N) in the soil. Through crop rotation and use of organic fertilizers the soil can be maintained; but higher yielding crops require either a large amount of organic or commercial fertilizer. Continually growing the same crop on the same fields will deplete the soil in its needed plant nutrients and the crop yields will continually go down or cease—the crop removes the nutrients till they are too low to support good growth. One way around this problem is to move to new land and start over. Even before 1100 Britain was too well developed to find much more arable land with about one third of its about 39,000,000 acres already put to crop use (about the same as today) with about another third in pasture and the final third composed of waste, forest, villages etc. England's slash-and-burn agricultural stage was largely behind it.
A crop takes from its field 1.3-2.0% of its weight in nitrogen (N), 0.13–0.3% in phosphorus (P) and 1.0–2.0% in potassium (K) and other needed trace minerals. The carbon, hydrogen and oxygen that constitute about 96% of the weight of a typical plant are turned into organic growth by CO2 in the air and H2O from the soil plus dissolved plant nutrients in the soil. Plants grow by undergoing photosynthesis using the sun's energy, CO2, H2O and the major plant nutrients nitrogen (N), phosphorus (P) and potassium (K) plus other nutrients. Twenty bushels of wheat (60 lb/bu) taken from a one acre field takes about 20 pounds of N with it, 100 bu/acre will remove about 100 lbs. N/acre, etc. In nature nearly all of these nutrients are normally in some sort of equilibrium with the plant nutrients returned to the soil when the plants or animals that eat the plants die. When you remove a crop this equilibrium state is disturbed. To restore the soil's fertility after it has been cropped for a while the missing nutrients have to be replaced either by judicious plant rotations or using organic or chemical fertilizers.
Fertilizers and manure 
|Common Manure N:P:K Ratios|
|Dairy Cow Manure||0.25||0.15||0.25||14|
|Sea Bird Guano||11–16||8–12||2–3||-|
The British Agricultural Revolution would not have been possible unless they learned how to maintain and restore the fertility of the soil as needed plant nutrients were removed with the crops. When animals eat a plant (or other animal) about 80–90% of the plant's nutrients absorbed by the plant from the soil pass though the animal and are excreted as urine and manure. It was widely known for centuries that manure was a good organic fertilizer that could be used to restore or enhance the productivity of arable land. Manure and urine have many of the nutrients absorbed in growing the crops and when regularly applied to the soil restores the plant nutrients to allow the growing of the same or larger crops on the same land. One advantage of organic fertilizers (manures) is that they tend to decompose slowly releasing their plant nutrients giving a long term boost to the plant nutrients. In addition, they add organic matter to the soil that helps retain water in the soil and keeps the soil looser for easier plant growth.
One of the major advantages of manure and other organic fertilizers is that in addition to the major macro nutrients common in commercial fertilizers, nitrogen (N):phosphorus (P): potassium (K), they also contain needed plant macro and micro-nutrients like sulfur (S), calcium (Ca) and other nutrients. Different types of organic fertilizers have different ratios of the macro-nutrients N:P:K plus other micro and macro nutrients.
One major disadvantages of organic fertilizers is that they have low concentrations of plant nutrients so that the collection, treatment, transportation and distribution or organic fertilizers are all potentially expensive. If organic fertilizers have to be hauled too far or handled too much they are not economical to use. For example, if it is determined that 100 kg/acre of nitrogen fertilizer is needed to be added to maintain a wheat field, etc. this would involve distributing about 20 tonnes of cow manure on the one acre plot to get the required nitrogen fertilizer. Another major disadvantage of manure and other organic fertilizers is that they lose 30–40% of the nutrients that typically leach away before or after they are applied. Much of the nitrogen in manure is locked up in organic components (amino acids etc.) that slowly decay so even in the second year it is not unusual for 20–30% of the initial nitrogen in the organic fertilizers to be available. Manure and other organic fertilizers were about the only fertilizer that was available to be regularly added to the soil before techniques were developed in the mid-1850s for phosphorus and potassium fertilizers and the early 1900s to make commercial nitrogen fertilizers.
If the plant nutrient levels are to be kept high enough to continue growing large crops on the same soil some type of fertilizer is nearly always needed. The manure is provided by the animals from the grain, hay and grass they eat and has to be distributed where it is needed to maintain the plant nutrient levels. Human manure (known as nightsoil) has an N:P:K ratio of 0.51:0.1:0.23 and was commonly used in market gardens around London from the 1600s to the late 1800s to help grow vegetables for the London market. Urine can contain about 95% water and up to 90 percent of the N (nitrogen), up to 50 percent of the P (phosphorus) and up to 70 percent of the K (potassium) present in excreta and is also a good though dilute fertilizer.
Manure spreaders are still used today to help distribute this natural fertilizer. Application of waste products to agricultural land is an efficient method of recycling them, while at the same time improving the productive capacity of soils Manure still provides significant organic plant nutrients (fertilizer) to soil and significantly reduces the need for commercial fertilizers.
Naturally occurring organic materials like kelp; seaweed; sawdust; wheat, rye, oat and pea straw; pig, sheep, goat, chicken, pigeon, horse, cow dung; cow and horse urine; feathers; leaves of trees; compost; bat or sea bird guano; ground bone; blood meal; dried blood, oyster shells; sea shells; rotten food; wood ash; coal and wood soot; cow hair; horn shavings; rags and many other organic substances were all tried with various degrees of success. By 1850 all these substances (and more) had experimental ratings in the literature with cow manure as the standard.
Naturally occurring mineral deposits like limestone, rock phosphates, Chilean sodium nitrate (saltpetre), all have significant amounts of needed plant nutrients and were all discovered by 1830 and used on a trial and error basis. Not surprisingly, in light of what is now known, different soils were deficient in different plant nutrients and different additives helped some soils more than others. Chilean saltpetre (discovered in Britain about 1830) and bat and sea bird guano were found so advantageous that a large market developed for them and they were being bought and shipped half way around the world for use on British farms by 1850.
One of the major disadvantages that farmers had till the late 1800s is that chemistry was just getting established on a scientific basis in this time period and the farmers did not know what minerals were needed in their soil as plant nutrients or what different organic compounds were available to fill these needs. There was no way to test the soil to see what plant nutrients were missing or what plant nutrients were in various inorganic and organic fertilizers. Manure and other soil additive applications were nearly always on a trial and error basis; but some applications were successful and various manuring practices gradually evolved as helping to keep and restore the soil so it could continue to grow larger crops. In general it was found that adding any organic matter to the soil helped it—some types helped more than others.
Animal urines are also useful organic fertilizers that are usually collected as part of the manure or bedding the animal uses. Many of the plant nutrients absorbed by animals are excreted in the urine. Urine is an aqueous solution of greater than 95% water, with the remaining constituents, in order of decreasing concentration urea (C O(N H2)2), 9.3 g/L, chloride (Cl) 1.87 g/L, sodium (Na) 1.17 g/L, potassium (K) 0.750 g/L, creatinine (C4N 3H7O) 0.670 g/L and other dissolved ions, inorganic and organic compounds. The nitrogen in the urea and creatine will break down to nitrate ions, which are readily absorbed by plants so urine can (and is) used as a type of organic fertilizer. One of the drawbacks of urine is it contains some salt (NaCl) that some plants are not very tolerant of. A typical human will excrete about 2.6 kg of N in a year—in about 500 litres of urine. Urine is normally very sterile and its main drawback is that it is a dilute fertilizer (N:P:K= 0.4:0.04:0.08) that has the usual problems of economical collection, treatment, transportation and distribution. Before use it is normally diluted about a factor of ten with water.
If legume plants like clover, peas, beans, etc. are planted they have a symbiotic relationship with bacteria (rhizobia) found on their root nodules that allows these plants to use nitrogen out of the air for their own growth and fix atmospheric nitrogen (NH3) in the soil. The ability to form this mutualism reduces fertilizer costs for farmers and gardeners who grow legumes, and allows legumes to be used in a crop rotation sequence to help replenish soil that has been depleted of nitrogen. If these legumes are ploughed under after one or two years growth they are a form of green manure that helps restore the N level in the soil even better. Legume crops have about 60–80% of the N they produce in their foliage available for hay production or animal grazing. Even if the plants are eaten the manure these animals produce will still have most of the N enhancement.
Compost is recycled organic matter that has been allowed to partially or completely decompose and can be used as a fertilizer and soil amendment. Before the advent of chemical fertilizers compost was (and still is) a key ingredient in organic farming. At the simplest level, the process of composting simply requires making a heap of wetted organic matter (leaves, food waste, grass, wood chips, etc.) and waiting for the materials to decay into humus over a period of weeks or months. Composted material can then be spread as a soil additive to get better yields, better weed control and better control of the moisture content of the soil. On a volume basis a good quality soil is one that is 45% minerals, 25% water, 25% air, and 5% organic material, both live and dead.
Maximizing crops 
|Crop Yield net of Seed
During the Middle Ages, the open field system had initially used a two field crop rotation system where one field was left fallow or turned into pasture for a time to try to recover some of its plant nutrients. Later they employed a three year, three field crop rotation routine, with a different crop in each of two fields, e.g. oats, rye, wheat and barley with the second field growing a legume like peas or beans with the third field fallow. Each field was rotated into a different crop nearly every year. Over the following two centuries, the regular planting of legumes such as peas and beans in the fields that were previously fallow slowly restored the fertility of some croplands. The planting of legumes helped to increase plant growth in the empty field due to the bacteria on legume roots ability to fix nitrogen (N2) from the air into the soil in a form that plants could use it. Other crops that were occasionally grown were flax and members of the mustard family.
One way to get more land to grow food on is to cut down on the amount of land left fallow to try to recover some of its plant nutrients. Normally from 10–30% of the arable land in a three crop rotation system is fallow. The British Agricultural Revolution was aided by land maintenance advancements in Flanders, and the Netherlands. Due to the large and dense population of Flanders and Holland, farmers there were forced to take maximum advantage of every inch of usable land, the country had become a pioneer in canal building, soil restoration and maintenance, soil drainage and land reclamation technology. Dutch experts like Cornelius Vermuyden brought some of this technology to Britain. The farmers in Flanders (in parts of France and current day Belgium) discovered a still more effective four-field crop rotation system, using turnips and clover (a legume) as forage crops to replace the three-year crop rotation fallow year. "Turnip" Townshend and others introduced to England the four-field crop rotation pioneered by farmers in the Flanders, Belgium region in the early 16th century.
The four field rotation system allowed farmers to restore soil fertility and restore some of the plant nutrients removed with the crops. Turnips first show up in the probate records in England as early as 1638 but were not widely used till about 1750. Fallow land was about 20% of the arable area in England in 1700 before turnips and clover were extensively introduced, and steadily declined to reach only about 4% in 1900. Ideally, wheat, barley, turnips and clover would be planted in that order in each field in successive years. The turnips helped keep the weeds down and were an excellent forage crop that ruminant animals could eat their tops and roots through a large part of the summer and winters. There was little need to let the soil lie fallow as Clover would re-add nitrates (Nitrogen-containing salts) back to the soil through the root nodules attached to them, which harboured symbiotic bacteria. These bacteria take nitrogen from the atmosphere and in turn produce the nitrates needed by the plants. Some nitrates are left in the soil when the plant dies are is ploughed under. The clover made excellent pasture and hay fields as well as green manure when it was ploughed under after one or two years. The addition of clover and turnips allowed more animals to be kept through the winter, which in turn produced more milk, cheese, meat and manure, which allowed the grain fields to be fertilized better—a virtuous circle.
Another way to get more land was to convert some pasture land into arable land and recover fen land and some pastures. It is estimated that the amount of arable land in Britain grew by 10–30% through these land conversions.
Water-meadows were utilized in the late 16th to the 20th centuries and allowed earlier pasturing of livestock after they were wintered on hay, etc. This increased livestock yields giving more hides, meat, milk and manure as well as better hay crops.
Crop rotation is the practice of growing a series of dissimilar types of crops in the same area in sequential seasons to help restore plant nutrients and it helps mitigate the build-up of pathogens and pests that often occurs when one plant species is continuously cropped, and can also improve soil structure and fertility by alternating deep-rooted and shallow-rooted plants. The Norfolk System, as it is now known, rotates crops so that different crops are planted with the result that different kinds and quantities of nutrients are taken from the soil as the plants grow.
The mix of crops also changed, replacing some low-yielding types, such as rye, with higher-yielding types such as wheat or barley. Grain yields also increased as new and better seed was introduced. Wheat yields increased by about 25% between 1700 and 1800, and then by about another 50% between 1800 and 1850.
Fences and enclosures 
To manage agricultural land and livestock productively they usually have to be separated. Domesticated livestock if let loose can and often destroy or damage a crop or over graze a pasture. Historically, the control of animals has often meant the hiring of a pig, cow, sheep, horse herders to control the movements of the animals. To minimize cost, herds of a particular village were often combined to allow less herders. Often the animals were brought back to village at night for fertilizing, feeding, milking, shearing, slaughtering or shelter. Flocks of livestock were often put in small fenced fields at night to spread their manure there. The manure came from digested food eaten by the livestock in a large pasture or fallow area during the day. Fences consisting of wooden stakes, rocks, hedges and later metal fences of netting and barbed wire minimized the need for these herders. Fences nearly always marked the boundaries of different farm properties that were bought, sold or rented to different farmers. These separate fields in turn allowed farmers to use more labour or capital intensive techniques to grow more food. Since Yeomen and husbandmen did most of the farm work with their own family and a few hired workers, more productive farms allowed more "extras" to be bought by the families and workers. These in turn provided the incentives needed to grow more food.
Fences are often needed to improve livestock herds. Selected animals are chosen and bred through several generations to develop a particular breed. These animals need to be raised separately from common flocks to control the selective breeding cycle. Often selected horse studs, bulls, rams, boars, roosters, etc. are bought and bred with the goal of improving the herds. Often "choice" animals are bred to other animals as a source of income.
Prior to the 18th century, agriculture had been much the same across Europe since the Middle Ages. The open field system was essentially feudal, with many subsistence farmers-cropping strips of land in one of three or four large fields held in common and splitting up the products likewise. The work was typical performed under the auspices of the Aristocracy or the Catholic Church who owned much of the land.
Beginning as early as the 12th century, some of the common fields in England tilled under the traditional open field system were enclosed into individually owned fields. The Black Death in 1349 and on essentially broke up the feudal system in England. To get more yield from a farm required a more secure control of the land—improvements are seldom made to "community" or commonly owned property. Many farms were bought by Yeomen who enclosed their property and improved the use of their land. Other husbandmen rented property they "share cropped" with the owners of the land. The process of enclosing property accelerated in the 15th and 16th centuries. This led to some villagers losing their land and their grazing rights and left many unemployed. English Poor Laws were enacted to help get over these adjustments and many started migrating to the cities looking for work. Only a few found work in the (increasingly mechanized) enclosed farms for good. Many relocated to the cities or colonies to try to find their fortune or work in the emerging factories of the Industrial Revolution. Many of these enclosures were accomplished by acts of Parliament in the 16th and 17th centuries. Some of the practices of enclosures were denounced by the Church, and legislation was drawn up against it; but the developments in agricultural mechanization during the 16–18th century required large, enclosed fields to be successfully workable to provide more food for all. All this controversy led to a series of government acts, culminating in the General Enclosure Act of 1801, which sanctioned large-scale land reform.
By the end of the 18th century the process of enclosure was largely complete.
British agriculture 1800–1900 
% per Yr.
Britain in 1800 was well under way on its Industrial Revolution and being ahead of most of the rest of the world could make and sell some products cheaper than anyone else. Initially this advantage was in the textile industry but soon the British use of coal, iron smelters and steam power for trains, ships, factories, agriculture, etc. were rapidly increased and very competitive. New agricultural implements were invented at an increasing pace all through the 1800s allowing agricultural populations in Britain to actually decrease. Some of this new capital generated by the Industrial Revolution was plowed back into agriculture to make the crop yields larger.
New fertilizers, besides the organic fertilizers in manure, were slowly found as massive sodium nitrate (NaNO3) deposits found in the Atacama Desert, Chile, were brought under British financiers like John Thomas North and imports were started. Chile was happy to allow the exports of these sodium nitrates by allowing the British to use their capital to develop the mining and imposing a hefty export tax to enrich their treasury. Massive deposits of sea bird guano, (11–16% N, 8–12% phosphate and 2–3% potash (KCl+)) were found and started to be imported after about 1830. Significant imports of potash (KCl+) obtained from the ashes of trees burned in opening new agricultural lands were imported. By-products of the British meat industry like bones from the knacker's yards were ground up or crushed and sold as fertilizer. By about 1840 about 30,000 tons of bones were being processed (worth about £150,000). An unusual alternative to bones was found to be the millions of tons of fossils called coprolites found in South East England. When these were dissolved in sulfuric acid they yielded a high phosphate mixture (called "super phosphate") that plants could absorb readily and increased crop yields. Mining coprolite and processing it for fertilizer soon developed into a major industry—the first commercial fertilizer. Higher yield per acre crops were also planted as potatoes went from about 300,000 acres in 1800 to about 400,000 acres in 1850 with a further increase to about 500,000 in 1900. Labor productivity slowly increased at about 0.6% per year. With more capital invested, more organic and inorganic fertilizers and better crop yields increased the food grown at about 0.5%/year—not enough to keep up with population growth.
The British population in 1800 was about 8.7 million increasing to 16.7 million in 1851 and 41.6 million by 1901. This corresponds to a rate of population increase from 1801 to 1851 of 1.84% per year and a rate of population increase of 3.00% per year from 1851 to 1901. Not only did the need for more food increase but the need for more shoes, clothes, carriages, horses, homes, furniture, etc. increased at the same or a greater rate as more products became available. Fortunately, the fast growing coal mining industry could provide plentiful coal for heating, etc. Unfortunately, burning all this coal gave London a severe smog problem during nearly all winter months. Canals and macadam roads helped lower the cost of transportation of coal, agricultural products, etc. The rate of population increase was much faster than the rate of increased agricultural yield per acre (hectare), which increased at about a rate of 0.5% per year from 1800 to 1850 and 0.2% per year from 1850 to 1900. Increased food imports were critical in feeding the rapidly growing urban population during the industrial revolution.
Needing massive amounts of more food the answer was to add more acres under cultivation and pasture. In addition to needing more land for cultivation there was also needed more pasture land to grow more poultry, livestock and draft horses and other agricultural products. The British Agricultural Statistics for this period show this competition for more land for cultivation and more land for pasturage in Britain was won by the need for more pasture as the arable land actually decreased from about 7.5 million hectares in 1800 to about 6.0 million hectares in 1900. The number of acres under wheat cultivation decreased from about 1.5 million hectares in 1800 to about 0.6 million hectares in 1900.
The only solution to this problem of rapidly increasing population and increased need for food and other agricultural products was to add more acres under cultivation and pasture. The way the food shortage was "solved" was to import much more food—use the acres in another country. Most of the British colonies (and ex colonies like the United States) had large acreage of potentially arable and pasture land. Countries that had agricultural surpluses they could export and trade for British industrial products were eager to do so until they could build up their own productive capacity. The products being produced in the British Industrial Revolution were easily traded for food and other products like wheat, meat, tea, cotton and wool, etc. needed in Britain.
So many cheap agricultural imports were coming into Britain after the Napoleonic Wars (1803–1815) and the resumption of American trade after the War of 1812 (1812–1815) that the Corn Laws (protective tariffs) were passed to protect cereal grain producers in Britain against competition from less expensive imports. These laws were in force between 1815 and 1846. The Corn Laws were removed in 1846 at the onset of the potato blight hitting much of Europe. The Irish Potato blight that ruined most of the Irish potato crop and brought devastation to the Irish people in 1846–50 also occurred in England, Wales and Scotland and the rest of Europe. The effect of the potato late blight (Phytophthora infestans) infestation on the potatoes common to Ireland, known today as Irish Potatoes, was much less in other countries since a much smaller percentage of the diet of the people of England, Wales, Scotland and the rest of Europe was centred on potatoes. In addition the citizens of Britain had the capital to buy and import more food from other countries — most of the Irish were too poor to do this. Several hundred thousand Irish died in the Irish potato famine and several hundred thousand more emigrated to England, Wales, Scotland, Canada, Australia, Europe and the United States. This massive Irish emigration continued till about 1921 when the population had been reduced from about 8.3 million in 1840 to 4.3 million by 1921.
The British Merchant Marine of this period was the largest in the world and easily capable of hauling most of the agricultural products needed. Other Merchant Navies were available to facilitate the trade not carried on British ships. There was so much trade going on that the United States of America, for example, paid for about 80–90% of their federal government through tariffs (customs) of about 10–20% on imports till the expenses of the American Civil War (1860–1865) forced new taxes. The British textile industry was hit hard by the American Civil War as the U.S. Navy blockaded southern ports and prevented the sale of cotton.
Between 1873 and 1879 British agriculture had wet summers that damaged grain crops. Cattle farmers were hit by foot-and-mouth disease, and sheep farmers by sheep liver rot. The poor harvests, however, masked a greater threat to British agriculture: growing imports of foodstuffs from abroad. The development of the steam ship and the development of an extensive railway networks in Britain and the USA allowed US farmers with much larger and more productive farms to export hard grain to Britain at a price that undercut the British farmers. At the same time, large amounts of cheap corned beef started to arrive from Argentina and the opening of the Suez Canal in 1869 and the development of refrigerator ships (reefers) in about 1880 opened the British market to cheap meat and wool from Australia, New Zealand, Argentina, etc. The Long Depression was a worldwide economic recession, that began in 1873 and ended around 1896. It hit the agricultural sector hard and was the most severe in Europe and the United States, which had been experiencing strong economic growth fuelled by the Second Industrial Revolution in the decade following the American Civil War. By 1900 half the meat eaten in Britain came from abroad and tropical fruits like bananas, etc. also were being imported on the new refrigerator ships.
Mechanization of agriculture 
Abraham Darby I (1678—1717) was the first, and most famous, of three generations with that name in an English Quaker family that developed a method of producing pig iron in a blast furnace fuelled by the much more available coke made from coal rather than charcoal produced from wood. Pig iron in turn was the precursor of cast iron and steel—a major ingredient of the Industrial Revolution. As iron and steel became ever more prevalent and cheaper they were used to make more cheaper metal tools and farm implements and ever more complicated metal farm implements. The production of "cheap" iron and steel was a key component of the mechanization of agriculture.
The main effect of mechanization and the addition of new farming implements, has been the increased productivity of each farm worker who can do more, sometimes several times more, work per day than he could without a particular mechanization. In the 1600s each agricultural worker grew enough food to feed about 1.25 people. Today each agricultural worker grows and harvests enough food to feed about 30 people. The mechanization of agriculture has been going on for centuries as new tools and capabilities were gradually adapted by farmers. Mechanization really took off after 1750 when new metal technologies made cheap steel and cast iron available and the development of steam power during the Industrial Revolution added another source of power on the farms that gradually displaced almost all of the others. The speed of mechanization has often been controlled by the size of the farm—small farms were seldom profitable enough to afford much new equipment. Typically this problem was "solved" by the farms consolidating into larger farms and/or sharing equipment—this process is still continuing today. Nearly always each new invention or mechanical device makes farm work less strenuous and faster.
The tools used by a farmer in the 1500 to 1700s could almost be carried in a small cart or wagon: shovels, axes, hoes, mattocks, rakes, pitchforks, scythes, cradles, flails, wooden ploughs, oxbows, chains, knives, scissors, saws, hammers, carts later horseshoes, horse collars and harnesses were added as the farmers switched from ox power to horse power. Initially many of these tools were made mostly of wood with the farmer creating them from the raw material available. The first farm work was done by hand with a hoe to cut down weeds and prepare the soil for planting with an axe or fire to help clear the forest for planting.
Animal power 
The first animal power to be widely applied to farming in Britain were usually oxen employed to pull ploughs, harrows, carts and wagons. Horses were primarily used as pack animals and for riding. The oxen were gradually displaced after 1700 by large work horses like the Shire horse and Clydesdale horse that were large horses that originally were bred to carry fully armoured knights. Horses became literally harnessed to the ploughs and wagons when the horse collar was widely adopted for use in Britain after about 1700. Oxen were gradually replaced since they did not take well to hard surfaced roads and were about 10% slower. Horses could be easily shod with iron horseshoes to protect their feet on hard surfaces. The horseshoes would typically wear out in 6–8 weeks and have to be replaced. Oxen could be shod also but this was a much more complicated process since cows have trouble standing on three feet and have cloven hoofs. Despite the fact that a large oxen is nearly as powerful as a large horse and had the advantage that they could be sold for food at the end of their lives they were gradually replaced. Oxen could also survive on poorer feed and unlike horses did not need supplements of grain to work over extended periods of time. Despite their advantages as draft animals cows after about 1800 they were primarily bred for either beef or dairy production and seldom as draft animals. So many more horses were brought into use and almost no oxen were being used by 1900. Starting in about 1850 large numbers of draft horses were imported from the US where they could be raised at lower costs. The horses were in turn gradually displaced after 1900 with the invention of the petrol powered tractor. Many small farmers could not afford the cost of a tractor and continued to use horses till well into the 1940s.
Weeding progressed from a hoe or mattock powered by a man or woman to a hand pushed wheeled metal cultivators with steel or iron blades. The new development of the seed drill that allowed some crops to be planted in straight rows allowed further weeding advances. Cultivators were enlarged so they often straddled several crop rows and were pulled by draft animals or after about 1920 by petrol engine powered tractors whose wheels straddled the rows. For mass control of weeds harrows pulled by draft animals or tractors with cupped shaped steel discs and/or serrated rotating toothed discs were developed to chop down and cut the weeds up.
Ploughs advanced from a forked wooden stick making a furrow (often called a hog plough because they root in and out of the ground) to an iron tipped wooden plough initially pulled mostly by oxen. Depending on the type of soil, a typical team of 2–6 oxen and 1–4 men could plough about one acre/day. Many crops required ploughing up to three times in a season to prepare the fields for planting. Joseph Foljambe's Rotherham cast iron plough of 1730, combining an earlier Dutch design with a number of technological innovations, was the first iron plough to have any commercial success in Europe. Its fittings and coulter were made of iron and the mouldboard and share were covered with an iron plate making it lighter to pull and more controllable than previous ploughs. It remained in limited use in Britain until the development of the tractor. It was followed by James Small of Doncaster and Berwickshire in 1763, whose "Scots Plough" used an improved cast iron share to turn the soil more effectively with less draft, wear, or strain on the ploughing team. Most teams pulling ploughs converted to horse drawn ploughs sometime after 1850. John Deere's self-polishing steel plough, invented in about 1837 in America, was used on some difficult soils or pasture land. Robert Ransome's plough factory of Ipswich, England was producing 86 different plough models designed for particular soils. Many ploughs had wheels added to the side or back of the plough that allowed the plough to be held vertically easier and raised or lowered easily for transport to different fields. Without wheels the plough had to be either dragged on its side or loaded and hauled in a cart. After about 1800 all these metal ploughs were made in quantity and at "reasonable" prices because of the production of cheap steel and iron produced by the development of the steel making industry in Britain.
Harrows are typically pulled by draft animals or tractors and are used for breaking up and smoothing out the surface of the soil in preparation for planting. Some harrowing may be done to keep down weeds or as a type of low impact tillage. Harrowing is often done on fields to smooth the rough soil finish often left by ploughing. When planting by broadcasting seed the seed is often spread over harrowed land and then buried to about the right depth for growth by lightly harrowing the soil again. Harrows almost always consist of a rigid frame to which are attached steel teeth (tines), cupped steel discs, linked chains or other means of smoothing or cultivating the soil. Tine and chain harrows are often only supported by a rigid towing-bar at the front of the set. The initial harrows were constructed out of simple wood frames with perhaps wooden stakes inserted as tines to help break up or smooth the ploughed ground to prepare a seedbed. Harrows seldom had riding accommodations provided for the teamsters. After tractors were introduced the farmer sat on the tractor while towing the harrow. Some harrows, often called discs, are made with revolving self-cleaning circular cupped steel discs that cut up, loosen over turn and smooth the soil. On some soils larger versions of these discs can sometimes be used instead of ploughs. Other harrow types that were invented include drag tooth harrows, chain harrows and power harrows or cultivators, which have petrol engine powered rotating L-shaped tines. Harrows showed the same progression of wood construction, some cast iron parts, nearly all iron to wholly steel that were initially pulled mostly by oxen, then horses, which were in turn replaced by tractors starting about 1900.
Seed planting 
Jethro Tull made early advancements in planting crops with his seed drill (1701)—a mechanical seeder that sowed seeds efficiently at the correct depth and spacing and then buried them so they could grow. Before the introduction of the seed drill, the common practice was to plant seeds by broadcasting (evenly throwing) them across the ground by hand on the prepared soil and then lightly harrowing the soil to bury the seeds to the correct depth. Other seeds were laboriously planted one by one using a hoe and or a shovel. By 1850 the seed drill had competition with mechanical broadcast seeders with a crank that more evenly sprayed seed over the ground. Some broadcasters were combined with a wheelbarrow to allow more seed to be easily carried and distributed.
Over 50 other inventors of improvements helped make his initial seed drill a machine in common use by 1900. It took a century and a half after the publication in 1731 of his Horse hoeing husbandry for farmers to widely adopt the technology. Although a pioneer in Europe, Tull was not the first to invent or use a seed drill; its origins can be traced back thousands of years to the East and China and other parts of Asia. The advantages of the drill were that it was faster and it could be set up to plant seeds evenly to make weeding easier. The disadvantages were it was a new "expensive" machine that only worked well on particular soils and usually did not significantly increase crop yields. Today many seed drills use air pipes that allows the seeds to be blown from a bin to a group of disk "coulters" set at the desired row spacing that cut slots in the ground into which the regulated amount of seeds fall. Behind the coulters are spring tines, which help to cover the seed up.
Manure spreading 
Manure spreaders used to distribute manure over a field as a fertilizer evolved from a simple farm cart to dedicated wagons or carts that was not used for other purposes. The first successful automated manure spreader was designed by Joseph Kemp in 1875. This and later manure spreaders used a drag chain to pull a board at one end of a manure filled wagon that forced the manure into a series of rotating tines that spread the manure more evenly. The power for the drive chain and rotating tines came from a connection to the rotating axle driven by the tires. They now have manure spreaders of several different types that work on dry, solid and slurry manures as well as irrigation systems.
Hay is grass or legumes like clover and alfalfa or other herbaceous plants that have been cut, dried, and stored for use as animal fodder. It is typically used to feed grazing livestock such as cattle, horses, goats, and sheep during the winter or other times when food is scarce. The hay originally was cut with scythes, dried and collected with rakes and then put onto a wagon pulled by oxen or horses to a haystack where it was stacked for winter use. The first major improvement seen in haying after about 1850s was when the sickle bar mowing head with its many triangular shaped knives mounted on a reciprocating long rod pulled by a team of horses was introduced. The cutting head extended to the side of the mower and the power for the reciprocating knives on the mower head was provided by the rotating wheels supporting the mower and driver. Horse drawn: mowers, rakes, haystackers etc. were some of the first improvements seen in haying sometime in the mid-1850s and on. By the late 1920s these machines were largely replaced by tractor drawn haying implements (many made originally for horses). Growing, cutting and storing the hay can be a long laborious process done two, three or more times per year. Today hay is cut with wide hay mowers and left to dry. It is then raked into rows where is picked up by large balers that collect the cut and raked crop and then compress the hay into compact bales that are easy to handle, transport and store. The compressed bales are held together by baling wire or twine. The original balers made rectangular bales that were typically loaded, hauled and stacked into haystacks by hand. Today, some of the balers now make bales of hay that are rectangular or round and can weigh anywhere from 1,100 to 2,200 pounds (500 to 1,000 kg) each and have to be handled with powered equipment.
Grain was originally harvested by cutting the grain with a sickle or scythe, tying the grain in bundles that were gathered into sheaves and allowed to dry before being brought to a harvesting barn by wagon where the grain was beat with hand powered flails to separate the grain kernels from its stem. The grain straw was collected and then hauled off for other uses. The next operation was to separate the chaff from the grain kernels by throwing it into the air in a wind and letting the heavier gain fall to the floor while the chaff blew away. The grain was then typically sacked for storage or sale. Wagons were again used to haul off the grain and straw. Harvesting was a very time consuming and laborious process that usually involved nearly all able bodied people on a farm or in a village for a period of several weeks.
The reaper used many reciprocating serrated triangular shaped knife blades spaced about two inches (5 cm) apart riveted onto a long metal rod 3 to 20 feet, (1–7m) long, the sickle bar, to cut the grain. The sickle bar's, guard plates mounted on each side of each knife blade holds the grain while the reciprocating sickle bar's knives sheared the grain off. A hair clipper works much the same way on a smaller scale. The cutting knives are protected against hitting most rocks by allowing the sickle bar to move up and down and putting steel projections (called point guards) in front of the knives. If a rock is hit the sickle bar rises as it is forced to go over the top of the rock and blade damage is avoided. The toothed knife blades mounted on the sickle bar can easily be individually replaced if they get dull or damaged. The rotating reel above the cutter bar holds the grain against the sickle bar knives and pushes the cut grain onto the bed of the reaper after it is cut. The cut grain was raked by another person riding on the reaper into rows awaiting other workers who bundled the grain into sheaves. The reaper was pulled by a team of two horses walking at the side of the grain allowing the reaper to by pulled instead of pushed by the draft animals. The reaper driver and a helper that removed the grain into rows for later binding, etc. usually rode on the reaper. An improved grain cutting blade (a sickle bar with replaceable serrated triangular shaped teeth) acquired in 1850 made the reaper much more efficient. The long involved harvesting process was still there only the grain cutting was easier and faster. A later improvement showing up in about 1870 was a reaper-binder that cut the grain and tied it into bundles ready for collection and harvesting. A still later improvement used a type of conveyor belt behind the reel to load the gain and stalks directly into a wagon traveling next to the reaper. The wagons hauled the cut grain to the thresher where the gain was separated from its stalk and chaff. The horse pulled reaper had to stop until a new wagon could be driven up to collect the cut grain.
The thrashing machine, or, in modern spelling, threshing machine (or simply thresher), was a machine first invented by Scottish mechanical engineer Andrew Meikle for use in harvesting grains. It was invented (c.1784) for the separation of grain from stalks and husks (straw). Many other farmers and inventors improved the original design over many years. Power for the thresher came initially from a team of about six to eight horses walking in a circle around a bullwheel, which was connected by long belt, which powered all the different thresher parts. The original thresher was stationary with stemmed grain fed to it manually and the separated grain and straw removed manually. The separated grain was usually put in sacks that were sown together by two men who sewed up to 1,000 sacks a day. Other workers were needed to drive wagons to load, deliver and unload the grain to where it was stored and haul off the straw. A harvest crew could be as large as 18 to 30 people with 20 to 30 horses used to power all the wagons and the thresher. One of the first improvements made was to replace the bullwheel and its teams of horses with a stationary steam engine turning a large pulley and a long wide leather belt(s) to power the thresher and its various moving parts. Steam tractors were often made to be primarily stationary steam engines needed to power threshers, etc. and used coal, wood or straw to make steam.
The cut grain and stems (straw) were originally put by hand into the thresher, which was stationary as the grain with its heads, stems and chaff was brought to it. The threshing mechanism consisted of a rotating threshing drum (commonly called the "cylinder"), to which grooved steel or hard rubber bars (rasp bars) are bolted. These rotating bars pulled the grain through the thresher. The rasp bars thresh or separate the separate grain kernels in a grain head and the chaff from the stem through the action of the pushing and bending the grain head against the steel meshed grilled "half cylinder", or concave, through which grain kernels, chaff and smaller debris falls as they break off the stem. The straw or grain stem, being too long and light, is carried through the concave onto the straw walkers to be conveyed out of the combine at a separate outlet. A separate blower section in the thresher blows the lighter chaff off the grain to get a chaff free grain. The grain is heavier than the straw and chaff, which causes it to fall rather than "float" across from the cylinder/concave to the straw walkers. These machines were typically so large that it may take a team of 18 to 30 horses to move them from one harvest field to the next. The large harvest crew of 18 to 30 men typically stayed together for the whole season working 10–12 hour days seven days a week till the harvest was done. The cut grain, chaff and straw typically raised large clouds of dust the harvesting crews had to work in. Usually the women on the farm or adjacent farms being harvested by that crew prepared the meals for the men on the harvesting crew. Additional help was usually traded with other farmers and their families.
Combine harvesters 
A major improvement was to marry the reaper and the thresher in a single machine called a combine. The combine name derives from the fact that it combines three separate operations, reaping, threshing, and winnowing, into a single process. The first combines were made in the 1850s but it took till after the 1920s for them to become common. In the original versions the bullwheel and its teams of horses that powered the thresher was replaced with large steel drive wheels that turned as the whole combine apparatus was pulled across a grain field with large teams of up 24 to 30 horses. The wheel's outer surface turned the cutting bar and provided power for the thresher as the implement was pulled forward and the support wheels rotated. The swath bar with its sickle bar cutting head in the front of the combine cut the grain as it progressed. The large rotating reel above the cutter bar pushes the grain into the sickle bar and then pushes the cut grain onto the combine's first conveyor belt that delivered the grain to the threshing part of the combine. Soon power for the various mechanisms in the combine were powered by small steam engines mounted on the thresher and the power connection to the drive wheels was eliminated. These engines were replaced in turn by petrol engines as they became available after about 1900. As tractors became available they replaced the large team of horses used to pull the combine.
These types of pulled combines with petrol engine powered threshing mechanisms were used until the 1940s in some areas. One of the disadvantages found in pulling these often massive, top-heavy machines on hilly fields was the risk of overturning — an expensive and dangerous event. This was partially "solved" by constructing combines that could "lean" into the hill while their harvesting head was tilted to follow the sloping ground. Many small farmers could not afford to buy these expensive, complicated machines and either hired someone to custom cut their grain for a fee or used what "old" equipment they had. Combines increased the harvest speed, cut the crew needed to harvest the crops from over 30 workers down to today's two to three much more productive workers and made grain "cheap" enough to help feed the world.
The combine harvester of today, or simply combine, is a self-propelled machine typically powered by up to a 400 hp diesel engine. Among the crops harvested with a combine are wheat, oats, rye, barley, corn (maize), rice, soybeans, flax (linseed) and other grains. The grain is cut by removable cutting heads 20 feet (6.1 m) to 40 feet (12 m) wide designed for specific crops. The cut grain and stem is typically transported to the threshing mechanism in the combine by various conveyor belts. The separated grain is typically stored in a bin mounted on the combine. The bin has a movable auger system to empty its contents into an adjacent truck or wagon. Often the bins are emptied while the truck or wagon matches speeds and the combine continues its harvesting. The straw typically left behind on the field is the dried stems and leaves of the crop with the grain removed. This "straw" is either spread on the field by the combine for future use as organic fertilizer or raked and baled for livestock feed and bedding. The high cost (over USD $400,000 for some) of these combines has led to "custom" cutting where a combine or several combines are bought and run by an individual or company to cut many different farmer's fields for a fee. Custom cutting allows the cost of the combine to be spread over many farmers as a combine can often run over several weeks or months of operation. A combine with a 40 feet (12 m) cutting bar can harvest 80–200 acres (32–80 hectares) per 12–15 hour day and may be able to be run daily for nearly two months.
Replacement of animal traction by machines 
The first farm implements were pulled primarily by oxen. Stating about 1750 horses started replacing them as draft animals. The most popular draft horses in Britain were Clydesdale horses and Shire horses. By 1900 steam powered tractors began to replace horses on the larger farms. The first powered farm implements in the early 19th century were coal or wood burning portable engines – steam engines on wheels that could be used to drive mechanical threshers by way of a long wide flexible leather belts. These portable steam engines were typically so large and expensive that a threshing crew of from 8–18 men hauled the machines to separate farms where they threshed until done and then went on to the next farm. In a given season many farmer's crops would be threshed. Around 1850, the first steam powered traction engines and stationary engines were developed and adopted for agricultural use on large farms. The steam engines then used were often so large they often used a cord of wood or a ton of coal per day. Before about 1938, there were no large low pressure rubber tires made for farm machinery and all agricultural machinery, except farm trucks, travelled on steel tires.
A tractor' is a vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery used in agriculture or construction. Most commonly, the term tractor is used to describe a farm vehicle that provides the power and traction to mechanize agricultural tasks, especially (and originally) tillage but nowadays a great variety of tasks. Initially tractors were powered by steam and were typically so large that they could only be profitably used on very large farms. Agricultural implements may be towed behind or mounted on the tractor, and the tractor may also provide a source of power if the implement is mechanised. The first tractors were steam-powered ploughing engine. They were used in pairs, placed on either side of a field to haul a plough back and forth between them using a wire cable. Where soil conditions and farm size permitted (as in the United States) steam tractors were used to direct-haul ploughs, but in the UK and elsewhere ploughing engines were nearly always used for cable-hauled ploughing instead. Some steam-powered agricultural engines remained in use well into the 20th century until reliable internal combustion gasoline and diesel engines had been developed.
In 1892, John Froelich invented and built the first gasoline/petrol-powered tractor in Clayton County, Iowa, USA. After receiving a patent Froelich started up the Waterloo Gasoline Engine Company, investing all of his assets, which by 1895, all would be lost and his business resigned to become a failure. The original tractors when used to pull implements normally pulled farm implements originally designed and built to be pulled by teams of horses.
Selective breeding 
In England, Robert Bakewell and Thomas Coke introduced selective breeding (mating together two animals with particularly desirable characteristics), and inbreeding (the mating of close relatives, such as father and daughter, or brother and sister, to stabilize certain qualities) in order to reduce genetic diversity in desirable animals programs from the mid 18th century. Robert Bakewell cross-bred the Lincoln and Longhorn sheep to produce the New Leicester variety. These methods proved successful in the production of larger and more profitable livestock.
Effects on history 
Sound advice on farming began to appear in England in the mid-17th century, from writers such as Samuel Hartlib, Walter Blith and others, but the overall agricultural productivity of Britain started to grow significantly only in the period of the Agricultural Revolution. It is estimated that the productivity of wheat was about 19 bushels per acre in 1720 and that it has grown to 21–22 bushels in the middle of the eighteenth century. It declined slightly in the decades of 1780 and 1790 but it began to grow again by the end of the century and reached a peak in the 1840s around 30 bushels per acre, stabilising thereafter.
The Agricultural Revolution in Britain proved to be a major turning point in history. The population in 1750 reached the level of 5.7 million. This had happened before: in around 1350 and again in 1650. Each time, either the appropriate agricultural infrastructure to support a population this high was not present or plague or war occurred (which may have been related), a Malthusian catastrophe occurred, and the population fell. However, by 1750, when the population reached this level again, an onset in agricultural technology and new methods without outside disruption, and also the effects of sugar imports, allowed the population growth to be sustained.
The increase in population led to more demand from the people for goods such as clothing. A new class of landless labourers, products of enclosure, provided the basis for cottage industry, a stepping stone to the Industrial Revolution. To supply continually growing demand, shrewd businessmen began to pioneer new technology to meet demand from the people. This led to the first industrial factories. People who once were farmers moved to large cities to get jobs in the factories. The British Agricultural Revolution not only made the population increase possible, but also increased the yield per agricultural worker, meaning that a larger percentage of the population could no longer work in agriculture but could and/or had to work in these new, post–Agricultural Revolution jobs.
Towards the end of the 19th century, the substantial gains in British agricultural productivity were rapidly offset by competition from cheaper imports, made possible by advances in transportation, refrigeration, and many other technologies.
See also 
- Acemoglu, Daron and Robinson, James; Why Nations Fail: The Origins of Power, Prosperity, and Poverty; Publisher: Crown Business (2012); ISBN-978-0307719218
- Historical UK tax rates, Table 1, p. 40  Access 19 Aug 2012
- Herman, Arthur; How the Scots Invented the Modern World...; Publisher: Broadway (2002); ISBN 978-0609809990
- Clark, Greg; "Human Capital, Fertility... "  Accessed 29 Aug 2012
- Five Hundred Points of Husbandry, by Thomas Tusser
- Common Manure N:P:K Ratios  Accessed 9 Apr 2012
-  Accessed 9 Apr 2012
- NPK ratios common organic substances  Accessed 6 Apr 2012
- Sommers, L.E., 1977. "Chemical composition of sewage sludge and analysis of their potential use as fertilizers". J. Environ. Qual. 6, 225–229.
- Wilson, John M.; "Rural The Rural Cyclopedia of ...Agriculture..."; Edinburgh, A Fullerton Co. Stead's Place London; 1851; p. 339,340; free Goggle eBook  Accessed 23 Mar 2012
- Urine as fertilizer  Accessed 9 Apr 2012
- Apostolides , Alexander; "English Agricultural Output And Labour Productivity, 1250–1850: Some Preliminary Estimates"  Accesssed 21 Mar 2012
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