Saturday, 19 May 2012

Preventing Soil Erosion

Just thought I'd elaborate on what can be done to prevent or reduce soil erosion, taken from another textbook and some are my classwork. :) 

The world's population continues to increase, so farmers are going to have to produce more food in order to feed the extra numbers. This can only be done if the soil is protected and carefully managed. [Note: Soil is a renewable resource, but it needs careful management. In the UK, it takes about 400 years just for 1cm of soil to form, and it can take 12,000 years for soil to become deep enough for farming!]

Evidence suggests that in the year 2000, 20% of land that was arable (used/suitable for growing crops) in 1985 had been lost through erosion, desertification and conversion to non-agricultural uses. 

1. Terracing in Indonesia and the Philippines: Large areas of these two countries are covered in volcanic mountains which have steep slopes and fertile soil. Flat terraces (like giant steps) were first built on many of the hillsides, the terraces are flat and are fronted by a mud/stone wall known as a 'bund'. The bund traps rainwater and soil, allowing the rainwater time to infiltrate into the ground so surface run-off and the removal of topsoil is prevented.

2. Contour ploughing: This is ploughing around hillsides rather than up and down the slope. By ploughing parallel to the contours, the furrows trap rainwater and prevent the water from washing soil downhill. 

3. Strip cropping: This is when 2 or more crops are planted in the same field. One crop may grow in the shelter of a taller crop. It is harvested at a different time of the year and uses different nutrients from the soil. Often the crops are rotated from year to year. 

4. Animal welfare in Kenya (Controlled size of herds!): Large herds of cattle, goats, sheep and camels have long been considered a source of wealth and prestige in several African countries. Unfortunately, quantity, rather than quality, has tended to result in overgrazing. [Overgrazing: when pasture or grazing is unable to support the number of animals relying on it for food. The result is that vegetation cover declines and soil erosion sets in.]
The problem of overgrazing has increased partly because rainfall has become even less reliable and partly because of the rapidly growing population. 'Practical Action', a British organisation, is working with local people in several parts of Kenya. They are helping to train one person from each village to become a 'wasaidizi' or animal care worker. By recognising and being able to treat basic animal illnesses, the wasaidizi is improving the quality of local herds. As the quality improves there should be less need for so many animals so that, hopefully, overgrazing will be reduced. 

5. Stone lines ('magic stones') in Burkina Faso: This project, begun by Oxfam in 1979, uses appropriate technology, local knowledge and local raw materials. It involves all villagers collecting some of the many stones lying around their village. The stones are laid across the land to stop surface run-off following the all too rare heavy rainstorms. Water and soil are trapped. The water now has time to infiltrate instead of being lost immediately through surface run-off. The soil soon becomes deep enough for the planting of crops. Erosion is reduced and crop yields have increased by as much as 50%. The only equipment needed is a simple level, developed by Oxfam, to help keep the lines parallel to the contours. 

6. Shelter belts of trees block wind: trees block wind from blowing away loose, dry grains of soil so topsoil is not lost. 

7. Afforestation: Increasing vegetation cover would help slow run off and increase infiltration. Trees intercept rainfall so force of water doesn't hit the soil and wash it away, roots also bind soil particles together. 

8. Small hedged fields: hedges reduce surface run-off and allow time for infiltration so water is retained where it falls. 

9. Gully filled with soil and planted with grasses: prevent wearing of soil and reduce surface run-off. (gullies are like storm drains, they would carry away the rain and soil quickly)

10. Crop rotation and NO monoculture: Practice of growing a series of dissimilar types of crops in the same area in sequential seasons. So that crops don't exhaust nutrients in soil as different crops require different nutrients.

11. Fields left under grass in winter: after winter when snow melts it will infiltrate into soil and stimulate growth of the grass--allowing animals a place to graze, and may prevent ground from freezing hard completely. 

12. Fallow land: crop land that is not seeded for a season, serves to accumulate moisture in dry regions or to check weeds/plant diseases. 'Rests' the land, so soil nutrients can be replenished.

13. Natural fertiliser (manure) used wherever possible: manure puts vital nutrients back into the soil, maintaining its health. And animal manure could be cheaper than chemicals, especially if the farm has some livestock. 

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Note: This blog will no longer be updated as I finished IGCSEs in 2012. Sorry! :( If you are interested in buying IB notes though, please contact me. :)