Arable land

Modern arable agriculture typically uses large fields like this one in Dorset, England

Farmland in St Buryan parish looking south towards the sea

In geography and agriculture, arable land (from Latin arāre; “To plough, To farm”) is land that can be used for growing crops. It includes all land under annual crops (double-cropped areas are counted only once), temporary meadows for mowing or market and kitchen gardens and land temporarily fallow (less than five years). Abandoned land resulting from shifting cultivation is not included in this category. Data for arable land are not meant to indicate the amount of land that is potentially cultivable. Arable land is a category of agricultural land, which, according to Food and Agriculture Organization's (FAO) definition, additionally includes land under permanent or perennial crops, such as fruit plantations, as well as permanent pastures, for grazing of livestock. In 2008, the world's total arable land amounted to 1,387 Mha, and 4,908 Mha was classified as "agricultural land."

Although constrained by land mass and topology, the amount of arable land, both regionally and globally, fluctuates due to human and climatic factors such as irrigation, deforestation, desertification, terracing, landfill, and urban sprawl. Researchers study the impact of these changes on food production.

The most productive portion of arable land is that from sediments left by rivers and the sea in geological times. In modern times, rivers do not generally flood as often in areas employing flood control.

Non-arable land

Map of world percentage arable land

Water Buffalo ploughing rice fields near Salatiga, Central Java, Indonesia

Land which is unsuitable for arable farming usually has at least one of the following deficiencies: no source of fresh water; too hot (desert); too cold (Arctic); too rocky; too mountainous; too salty; too rainy; too snowy; too polluted; or too nutrient poor. Clouds may block the sunlight plants need for photosynthesis, reducing productivity. Starvation and nomadism often exists on marginally arable land. Non-arable land is sometimes called wasteland, badlands, worthless or no man's land.

However, non-arable land can sometimes be converted into arable land. New arable land makes more food, and can reduce starvation. This outcome also makes a country more self-sufficient and politically independent, because food importation is reduced. Making non-arable land arable often involves digging new irrigation canals and new wells, aqueducts, desalination plants, planting trees for shade in the desert, hydroponics, fertilizer, nitrogen fertilizer, pesticides, reverse osmosis water processors, PET film insulation or other insulation against heat and cold, digging ditches and hills for protection against the wind, and greenhouses with internal light and heat for protection against the cold outside and to provide light in cloudy areas. This process is often extremely expensive. An alternative is the Seawater Greenhouse which desalinates water through evaporation and condensation using solar energy as the only energy input. This technology is optimized to grow crops on desert land close to the sea.

Some examples of infertile non-arable land being turned into fertile arable land are:

• Aran Islands: These islands off the west coast of Ireland, (not to be confused with the Isle of Arran in Scotland's Firth of Clyde), were unsuitable for arable farming because they were too rocky. The people covered the islands with a shallow layer of seaweed and sand from the ocean. This made it arable. Today, crops are grown there.
• Israel: Israel's land primarily consisted of desert until the construction of desalination plants along the country's coast. The desalination plants, which remove the salt from ocean water, have created a new source of water for farming, drinking, and washing.
• Slash and burn agriculture uses nutrients in wood ash, but these expire within a few years

• Terra preta, fertile tropical soils created by adding charcoal.

Some examples of fertile arable land being turned into infertile land are:

• Droughts like the 'dust bowl' of the Great Depression in the U.S. turned farmland into desert.
• Rainforest Deforestation: The fertile tropical forests turn into infertile desert land. For example, Madagascar's central highland plateau has become virtually totally barren (about ten percent of the country), as a result of slash-and-burn deforestation, an element of shifting cultivation practiced by many natives.
• Each year, arable land is lost to desertification and erosion from human industrial activities. Improper irrigation of farm land can wick the sodium, calcium, and magnesium from the soil and water to the surface. This process steadily concentrates salt in the root zone, decreasing productivity for crops that are not salt-tolerant.

See also

• Fertility
• Land use statistics by country
• List of environment topics

External links

• Surface area of the Earth
• Article from Technorati on Shrinking Arable Farmland in the world