Crop rotation is the practice of growing a series of dissimilar types of crops A crop is the annual or season's yield of any plant that is grown in significant quantities to be harvested as food, as livestock fodder, fuel, or for any other economic purpose. This category includes crop species as well as agricultural techniques related to cropping in the same area in sequential seasons for various benefits such as to avoid the build up of pathogens A pathogen, (from Greek πάθος pathos "suffering, passion", and γἰγνομαι gignomai (gen-) "I give birth to") an infectious agent, or more commonly germ, is a biological agent that causes disease to its host. There are several substrates and pathways whereby pathogens can invade a host; the principal pathways have and pests that often occurs when one species is continuously cropped. Crop rotation also seeks to balance the fertility demands of various crops to avoid excessive depletion of soil nutrients. A traditional component of crop rotation is the replenishment of nitrogen Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere through the use of green manure In agriculture, a green manure is a type of cover crop grown primarily to add nutrients and organic matter to the soil. Typically, a green manure crop is grown for a specific period, and then plowed under and incorporated into the soil in sequence with cereals and other crops. It is one component of polyculture Polyculture is agriculture using multiple crops in the same space, in imitation of the diversity of natural ecosystems, and avoiding large stands of single crops, or monoculture. It includes crop rotation, multi-cropping, intercropping, companion planting, beneficial weeds, and alley cropping. Crop rotation can also improve soil structure Soil structure is determined by how individual soil granules clump or bind together and aggregate, and therefore, the arrangement of soil pores between them. Soil structure has a major influence on water and air movement, biological activity, root growth and seedling emergence and fertility Nitrogen is the element in the soil that is most often lacking. Phosphorus and potassium are also needed in substantial amounts. For this reason these three elements are always included in commercial fertilizers and the content of each of these items is included on the bags of fertilizer. For example a 10-10-15 fertilizer has 10 percent nitrogen, 1 by alternating deep-rooted and shallow-rooted plants.

Method and purpose

Crop rotation avoids a decrease in soil fertility, as growing the same crop Agriculture is the production of food and goods through farming. Agriculture was the key development that led to the rise of human civilization, with the husbandry of domesticated animals and plants creating food surpluses that enabled the development of more densely populated and stratified societies. The study of agriculture is known as repeatedly in the same place eventually depletes the soil Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics of various nutrients A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. Nutrients are the substances that enrich the body. They build and repair tissues, give heat and energy, and regulate body processes. Methods for nutrient intake vary, with animals and. A crop that leaches the soil of one kind of nutrient is followed during the next growing season by a dissimilar crop that returns that nutrient to the soil or draws a different ratio of nutrients, for example, rice followed by cotton. By crop rotation farmers can keep their fields In Australian and New Zealand English, any agricultural field may be called a paddock under continuous production, without the need to let them lie fallow, and reducing the need for artificial fertilizers Fertilizers are soil amendments applied to promote plant growth; the main nutrients present in fertilizer are nitrogen, phosphorus, and potassium and other nutrients ('micronutrients') are added in smaller amounts. Fertilizers are usually directly applied to soil, and also sprayed on leaves ('foliar feeding'), both of which can be expensive. Rotating crops adds nutrients to the soil, and dirt. Legumes A legume in botanical writing is a plant in the family Fabaceae , or a fruit of these specific plants. A legume fruit is a simple dry fruit that develops from a simple carpel and usually dehisces (opens along a seam) on two sides. A common name for this type of fruit is a pod, although "pod" is also applied to a few other fruit types,, plants of the family Fabaceae Fabaceae or Leguminosae is a large and economically important family of flowering plants, which is commonly known as the legume family, pea family, bean family or pulse family. The name 'Fabaceae' comes from the defunct genus Faba, now included into Vicia. Leguminosae is an older name still considered valid, and refers to the typical fruit of, for instance, have nodules on their roots In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating (growing up above the ground or especially above water). Furthermore, a stem normally occurring below ground is not exceptional either (see rhizome). So, it is which contain nitrogen-fixing Nitrogen fixation generally refers to the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia. This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g. nucleotides for DNA and amino acids for proteins. Formally, nitrogen bacteria The bacteria ( [bækˈtɪəriə] ; singular: bacterium)[α] are a large group of single-celled, prokaryote microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste,. It therefore makes good sense agriculturally to alternate them with cereals (family Poaceae Poaceae is a family in the Class Liliopsida (the monocots) of the flowering plants. Plants of this family are usually called grasses, or, to distinguish them from other graminoids, true grasses; the shrub- or tree-like plants in this family are called bamboo (there are also herbaceous, non-woody bamboos). There are about 600 genera and some 9,000�) and other plants that require nitrates The nitrate ion is a polyatomic ion with the molecular formula NO−3 and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identical oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a formal charge of negative one, where each oxygen carries. A common modern crop rotation is alternating soybeans The soybean or soya bean (UK) (Glycine max) is a species of legume native to East Asia. The plant is classed as an oilseed rather than a pulse. It is an annual plant that has been used in China for 5,000 years to primarily add nitrogen into the soil as part of crop rotation and maize Maize is a grass domesticated by indigenous peoples in Mesoamerica in prehistoric times. The Aztecs and Mayans cultivated it in numerous varieties throughout central and southern Mexico, to cook or grind in a process called nixtamalization. Later the crop spread through much of the Americas. Between 1250 A.D. and 1700 A.D. nearly the whole (corn). In subsistence farming Subsistence agriculture is self-sufficiency farming in which farmers grow only enough food to feed their families. The typical subsistence farm has a range of crops and animals needed by the family to eat during the year. Planting decisions are made with an eye toward what the family will need during the coming year, rather than market prices, it also makes good nutritional sense to grow beans and grain at the same time in different fields.

Crop rotation is a type of cultural control that is also used to control pests and diseases that can become established in the soil over time. The changing of crops in a sequence tends to decrease the population level of pests. Plants within the same taxonomic family What does and does not belong to each family is determined by a taxonomist. Similarly for the question if a particular family should be recognized at all. Often there is no exact agreement, with different taxonomists each taking a different position. There are no hard rules that a taxonomist needs to follow in describing or recognizing a family tend to have similar pests and pathogens. By regularly changing the planting location, the pest cycles can be broken or limited. For example, root-knot nematode Root-knot nematodes are plant-parasitic nematodes from the genus Meloidogyne. They exist in soil in areas with hot climates or short winters. About 2000 plants are susceptible to infection by root-knot nematodes and they cause approximately 5% of global crop loss . Root-knot nematode larva infect plant roots causing the development of root-knot is a serious problem for some plants in warm climates and sandy soils, where it slowly builds up to high levels in the soil, and can severely damage plant productivity by cutting off circulation from the plant roots. Growing a crop that is not a host for root-knot nematode for one season greatly reduces the level of the nematode in the soil, thus making it possible to grow a susceptible crop the following season without needing soil fumigation Fumigation is a method of pest control that completely fills an area with gaseous pesticides—or fumigants—to suffocate or poison the pests within. It is utilized for control of pests in buildings , soil, grain, and produce, and is also used during processing of goods to be imported or exported to prevent transfer of exotic organisms. This.

It is also difficult to control weeds A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-made settings such as gardens, lawns or agricultural areas, but also in parks, woods and other natural areas. More specifically, the term is often used to describe native or nonnative plants that grow similar to the crop which may contaminate the final produce. For instance, ergot Ergot or ergot fungi refers to a group of fungi of the genus Claviceps. The most prominent member of this group is Claviceps purpurea. This fungus grows on rye and related plants, and produces alkaloids that can cause ergotism in humans and other mammals, consuming grains contaminated with the fruiting structure of this fungus. There are about 50 in weed grasses is difficult to separate from harvested grain. A different crop allows the weeds to be eliminated, breaking the ergot cycle.

This principle is of particular use in organic farming Organic farming is the form of agriculture that relies on crop rotation, green manure, compost, biological pest control, and mechanical cultivation to maintain soil productivity and control pests, excluding or strictly limiting the use of synthetic fertilizers and synthetic pesticides, plant growth regulators, livestock antibiotics, food additives,, where pest control Biological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms. It can be an important component of integrated pest management (IPM) programs may be achieved without synthetic pesticides.

A general effect of crop rotation is that there is a geographic mixing of crops, which can slow the spread of pests and diseases during the growing season. The different crops can also reduce the effects of adverse weather for the individual farmer and, by requiring planting and harvest at different times, allow more land to be farmed with the same amount of machinery and labor.

The choice and sequence of rotation crops depends on the nature of the soil Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics, the climate Climates encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elements in a given region over long periods of time. Climate can be contrasted to weather, which is the present condition of these same elements and their variations over periods up to two weeks, and precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that is pulled down by gravity and deposited on the Earth's surface. The main forms of precipitation include rain, snow, ice pellets, and graupel. It occurs when the atmosphere, a large gaseous solution, becomes saturated with water vapour and the water which together determine the type of plants that may be cultivated. Other important aspects of farming such as crop marketing and economic variables must also be considered when choosing a crop rotation.

History

Historic crop rotation methods are mentioned in Roman The Roman Empire was the post-Republican phase of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean. The term is used to describe the Roman state during and after the time of the first emperor, Augustus literature, and referred to by several civilizations in Asia Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.6% of the Earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population. During the 20th century Asia's population nearly quadrupled and Africa Africa is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area. With a billion people (as of 2009, see table) in 61 territories, it accounts for about 14.72% of the world's human population. During the Muslim Agricultural Revolution The Arab Agricultural Revolution is a term coined by the historian Andrew Watson in his influential 1974 paper postulating a fundamental transformation in agriculture from the 8th century to the 13th century in the Muslim lands. This was an extension of an earlier hypothesis of an agricultural revolution in Islamic Spain proposed much earlier in 18, a rotation system was developed where land was cropped four times or more in a two-year period. Winter crops were followed by summer ones, and in some cases there was a crop in between. In areas where plants of shorter growing season were used, ie.spinach Spinach is an edible flowering plant in the family of Amaranthaceae. It is native to central and southwestern Asia. It is an annual plant (rarely biennial), which grows to a height of up to 30 cm. Spinach may survive over winter in temperate regions. The leaves are alternate, simple, ovate to triangular-based, very variable in size from about 2-30 and eggplants The eggplant, aubergine, melongene or brinjal is a plant of the family Solanaceae (also known as the nightshades) and genus Solanum. It bears a fruit of the same name, commonly used as a vegetable in cooking. As a nightshade, it is closely related to the tomato and potato and is native to Nepal, India, Bangladesh, Pakistan, and Sri Lanka, the land could be cropped three or more times a year. According to some sources, in parts of Yemen Yemen , officially the Republic of Yemen (Arabic: الجمهورية اليمنية al-Jumhuuriyya al-Yamaniyya) [[Media:Ar-al Gumhuriyah al Yamaniyyah.ogg|]] (help·info) is a country located on the Arabian Peninsula in Southwest Asia. It has an estimated population of more than 23 million people and is bordered by Saudi Arabia to the north, the wheat yielded two harvests a year on the same land, as did rice in Iraq.^[1] Scholars such as Andrew Watson have written of a Muslim agricultural revolution as the Islamic world made significant progress in developing a more "scientific" approach based on three major elements: sophisticated systems of crop rotation, highly developed irrigation techniques and the introduction of a large variety of crops which were studied and catalogued according to the season, type of land and amount of water they require. Numerous farming encyclopaedias were produced.

In Europe, since the times Charlemagne Charlemagne was King of the Franks from 768 and Emperor of the Romans (Imperator Romanorum) from 800 to his death. He expanded the Frankish kingdom into an empire that incorporated much of Western and Central Europe. During his reign, he conquered Italy and was crowned Imperator Augustus by Pope Leo III on 25 December 800. This temporarily made, there was a transition from a two-field crop rotation to a three-field crop rotation. Under a two-field rotation, half the land was planted in a year while the other half lay fallow. Then, in the next year, the two fields were reversed. Under three-field rotation, the land was divided into three parts. One section was planted in the Fall with winter wheat or rye. The next Spring, the second field was planted with other crops such as peas, lentils, or beans and the third field was left fallow. The three fields were rotated in this manner so that every three years, a field would rest and be unplanted. Under the two filed system, if one has a total of 600 fertile acres of land, one would only plant 300 acres. Under the new three-field rotation system, one would plant (and thereby harvest) 400 acres. But, the additional crops had a more significant effect than mere productivity. Since the Spring crops were mostly legumes, they increased the overall nutrition of the people of Northern Europe.^[2]

From the end of the Middle Ages The Middle Ages is a period of European history from the 5th century to the 15th century. The period followed the fall of the Western Roman Empire in 476, and preceded the Early Modern Era. It is the middle period in a three-period division of history: Classical, Medieval, and Modern. The term "Middle Ages" (medium aevum) was coined in until the 20th century, the three-year rotation was practiced by farmers in Europe with a rotation of rye Rye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe (Triticeae) and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskies, some vodkas, and animal fodder. It can also be eaten whole, either as boiled rye berries, or by being rolled, similar to rolled or winter wheat Wheat is a grass, originally from the Fertile Crescent region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize (784 million tons) and rice (651 million tons). Globally, wheat is the leading source of vegetable protein in human food, having a, followed by spring oats The common oat is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural, unlike other grains). While oats are suitable for human consumption as oatmeal and rolled oats, one of the most common uses is as livestock feed. Oats make up a large part of the diet of horses and are regularly fed to cattle as or barley Barley is a cereal grain derived from the annual grass Hordeum vulgare, then letting the soil rest (leaving it fallow) during the third stage. The fact that suitable rotations made it possible to restore or to maintain a productive soil has long been recognized by planting spring crops for livestock in place of grains for human consumption.

A four-field rotation was pioneered by farmers, namely in the region Waasland in the early 16th century and popularised by the British The United Kingdom of Great Britain and Northern Ireland[note 7] is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of the island of Ireland, and many small islands. Northern Ireland is the only part of the UK with a land agriculturist Charles Townshend Charles Townshend, 2nd Viscount Townshend PC was a British Whig statesman. He served for a decade as Secretary of State, directing British foreign policy. He was often known as Turnip Townshend because of his strong interest in farming, and his role in the British agricultural revolution in the 18th century. The system (wheat Wheat is a grass, originally from the Fertile Crescent region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize (784 million tons) and rice (651 million tons). Globally, wheat is the leading source of vegetable protein in human food, having a, turnips The turnip or white turnip is a root vegetable commonly grown in temperate climates worldwide for its white, bulbous taproot. Small, tender varieties are grown for human consumption, while larger varieties are grown as feed for livestock, barley Barley is a cereal grain derived from the annual grass Hordeum vulgare and clover), opened up a fodder crop and grazing crop allowing livestock to be bred year-round. The four-field crop rotation was a key development in the British Agricultural Revolution.

George Washington Carver pioneered crop rotation methods in the United States by teaching southern farmers to rotate soil depleting crops like cotton with soil enriching crops like peanuts and peas. [2]

In the Green revolution, the traditional practice of crop rotation gave way in some parts of the world to the practice of supplementing the chemical inputs to the soil through top dressing with fertilizers, e.g., adding ammonium nitrate or urea and restoring soil pH with lime in the search for increased yields, preparing soil for specialist crops, and seeking to reduce waste and inefficiency by simplifying planting and harvesting. Some disadvantages of this type of monoculture have since become apparent, notably from the perspective of sustainable agriculture and the risk of catastrophic crop failure.

Effects on soil erosion

Crop rotation can greatly affect the amount of soil lost from erosion by water. In areas that are highly susceptible to erosion, farm management practices such as zero and reduced tillage can be supplemented with specific crop rotation methods to reduce raindrop impact, sediment detachment, sediment transport, surface runoff, and soil loss.^[3]

Protection against soil loss is maximized with rotation methods that leave the greatest mass of crop stubble (plant residue left after harvest) on top of the soil. Stubble cover in contact with the soil minimizes erosion from water by reducing overland flow velocity, stream power, and thus the ability of the water to detach and transport sediment^[4] Soil Erosion and Cill prevent the disruption and detachment of soil aggregates that cause macrospores to block, infiltration to decline, and runoff to increase.^[5] This significantly improves the resilience of soils when subjected to periods of erosion and stress.

The effect of crop rotation on erosion control varies by climate. In regions under relatively consistent climate conditions, where annual rainfall and temperature levels are assumed, rigid crop rotations can produce sufficient plant growth and soil cover. In regions where climate conditions are less predictable, and unexpected periods of rain and drought may occur, a more flexible approach for soil cover by crop rotation is necessary. An opportunity cropping system promotes adequate soil cover under these erratic climate conditions.^[6] In an opportunity cropping system, crops are grown when soil water is adequate and there is a reliable sowing window. This form of cropping system is likely to produce better soil cover than a rigid crop rotation because crops are only sown under optimal conditions, whereas rigid systems are sown in the best conditions available.^[7]

Crop rotations also affect the timing and length of when a field is subject to fallow.^[8] This is very important because depending on a particular regions climate, a field could be the most vulnerable to erosion when it is under fallow. Efficient fallow management is an essential part of reducing erosion in a crop rotation system. Zero tillage is a fundamental management practice that promotes crop stubble retention under longer unplanned fallows when crops cannot be planted.^[6] Such management practices that succeed in retaining suitable soil cover in areas under fallow will ultimately reduce soil loss.

See also

• Companion planting, a traditional alternative to crop rotation in which multiple crops are grown together.
• Dryland farming, a specific form of crop rotation applicable to areas with limited precipitation.
• Ley farming, an agricultural system where the field is alternately seeded for grain and left fallow.
• Set-aside, a legislatively-imposed system of compulsory fallowing in modern Europe.
• Soybean management practices refers to the different practices that are utilized by soybean producers.
• Shmita, the seventh year of the Jewish seven-year agricultural cycle, where the land is left to lie fallow and all agricultural activity is forbidden by Torah law.

References

1. ^ Andrew M. Watson (1974), The Arab Agricultural Revolution and Its Diffusion, 700-1100, The Journal of Economic History, Vol. 34, No.1, The Tasks of Economic History, pp. 8-35.
2. ^ J.J Butt,Daily life in the age of Charlemagne, p.82-83 [1]
3. ^ Unger, P.W., and McCalla, T.M. “Conservation Tillage Systems.” Advances in Agronomy. Vol. 33. pg. 2-53. 1980.
4. ^ Rose, C.W., and Freebairn, D.M. “A mathematical model of soil erosion and deposition processes with application to field data.”
5. ^ Loch, R.J., and Foley, J.L. “Measurement of Aggregate Breakdown under rain: comparison with tests of water stability and relationships with field measurements of infiltration.” Australian Journal of Soil Research. Vol. 32. pg. 701-720. 1994.
6. ^ ^{a b} Carroll, C., Halpin, M., Burger, P., Bell, K., Sallaway, M.M., and Yule, D.F. “The effect of crop type, crop rotation, and tillage practice on runoff and soil loss on a Vertisol in central Queensland.” Australian Journal of Soil Research. Vol. 35. pg. 925-939. 1997.
7. ^ Littleboy, M., Silburn, D.M., Freebairn, D.M., Woodruff, D.R., and Hammer, G.L. “PERFECT. A computer simulation model of Productive Erosion Runoff Functions to Evaluate Conservation Techniques.” Queensland Department of Primary Industries. Bulletin QB89005. 1989.
8. ^ Huang, M., Shao, M., Zhang, L., and Li, Y. “Water use efficiency and sustainability of different long-term crop rotation systems in the Loess Plateau of China.” Soil & Tillage Research. Vol. 72. pg. 95-104. 2003.

External links

• Cyclopedia of American Agriculture ed. by L. H. Bailey (1911), Vol. II—Crops, Chapter V "Crop Management," primarily the history and theory of crop rotation.
• There is a Dutch article on crop rotation that has excellent illustrations (use of an internet dictionary is recommended). [3]
• Technology in the middle ages

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