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There are many causes of land degradation, which often overlap. The most common cause of land degradation is overgrazing, that is, when the animals eat plants so fast that vegetation has no chance to grow back. This leaves the soil bare, especially its humus layer. Wind and rainwater easily remove humus, which makes the soil lose its qualities. This is especially characteristic of arid and semi‑arid areas, such as the Sahel region of Africa. The effects of reckless deforestation are similar, only they can be seen much sooner.

Improper agricultural practices also contribute to the deterioration of soil quality. Prolonged overexploitation of land leads to a reduction of the amount of humus. As a result, the soil becomes poorer in nutrients and its structure deteriorates, causing reduced water absorption, inhibiting the activity of soil‑dwelling organisms and weakening its chemical stability.

An obvious solution would seem to be to use fertilisers. Natural ones are the best, but unfortunately they are usually hard to come by in sufficient amounts. Synthetic fertilisers, on the other hand, can be counterproductive when used improperly. For instance, too much can poison the soil, killing soil micro‑organisms, activating heavy‑metal compounds and changing the pH (increasing acidity) of the soil, which makes it more difficult for plants to absorb nutrients. Over‑fertilisationover‑fertilisationOver‑fertilisation is typical of developed countries where intensive farming is popular.

Soil degradationsoil degradationSoil degradation may also derive from incorrect use of chemical plant protection products. When such substances, toxic by their very nature, penetrate the soil, they kill soil‑dwelling organisms, disturbing, as a result, soil formation processes.

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Na zdjęciu zaorane pola uprawne o regularnym prostokątnym kształcie. W środkowej części pokryte białym nalotem - solą. Z lewej strony zdjęcia widoczny fragment wyschniętego pola - być może już po zebraniu zbiorów. W środku i z prawej strony ograniczony pas zieleni.

Even improper irrigation can have grave consequences. Water used in farming is often rich in salts. In the process of evaporation, only water particles enter the atmosphere, whereas mineral compounds remain in the soil. The amount of the latter grows with time, leading to soil degradation due to increased salinity. Soil salinitysoil salinitySoil salinity is a characteristic feature of arid areas in both developing and developed countries.

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Na ilustracji diagram kołowy. Przyczyny degradacji gleb na świecie - causes of soil degradation in the world. Trzydzieści pięć procent nadmierny wypas - excessive grazing, trzydzieści procent – wylesianie - deforestation, dwadzieścia siedem procent – działalność rolna - agricultural activity, siedem procent – nadmierne wykorzystanie roślin - excessive use of vegetation, na przykład jako opał, jeden procent – działalność przemysłowa - industrial activity.

Soil degradation can be also caused by some types of agricultural machinery. Machines used for harvesting crops are usually large and heavy, so they compact the soil. This, in turn, hinders gas exchange, water absorption, movement of animals living in the soil, but also makes it easier for water to run over the soil instead of entering it. All these factors combined impair the quality of the land or, in other words, lead to its degradation. Owing to the costliness of agricultural machinery, this type of degradation is typical of developed countries.

In addition to factors contributing to the degradation of soils on a global scale, there are also others that can only be relevant locally, for example, plowing on the steep slopes. In the case of a field plowed along the slope, soil degradation occurs much faster as a result of washing out the humus out of it than in the case of a contour plowing.

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Fotografia przedstawiająca pole zaorane wzdłuż stoku. Z prawej strony zdjęcia widoczny jest pas porośnięty polnymi kwiatami - chabrami i makami. Kolejny pas to fragment nieskoszonego zboża, a dalej ściernisko po żniwach, na którym pozostawiono bele słomy.

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Fotografia barwna przedstawiająca pole zaorane wzdłuż warstwic. Rośliny rosną na wzgórzu w wyraźnie oddzielonych rzędach. Niżej przebiega linia kolejowa, a jeszcze niżej na drodze widać samochody.

Keywords

soil salinity, land degradation, overgrazing

Glossary