The terracing system of farming is done where people have to grow their food on steep, erosion prone slops. In hillside regions of Mexico, this agricultural system is being practiced for over three hundred years.
Terracing slows the rate of soil erosion, caused by heavy rainfall thus, preventing the soil from losing fertility. The main aim is to minimize erosion as well as conserve water. After the rainfall, the terraces allow the captured water to slowly percolate into the fields for an efficient irrigation.
Below Terracing info from Wikipedia (Read More):-
In agriculture, a terrace is a leveled section of a hill cultivated area, designed as a method of soil conservation to slow or prevent the rapid surface runoff of irrigation water. Often such land is formed into multiple terraces, giving a stepped appearance. The human landscapes of rice cultivation in terraces that follow the natural contours of the escarpments like contour plowing is a classic feature of the island of Bali and the Banaue Rice Terraces in Benguet, Philippines. In Peru, the Inca made use of otherwise unusable slopes by drystone walling to create terraces. This form of land use is prevalent in many countries, and is used for crops requiring a lot of water, such as rice. Terraces are also easier for both mechanical and manual sowing and harvesting than a steep slope would be.
Natural terracing, the result of small-scale erosion, is formed where cattle are grazed for long periods on steep sloping pasture. Sometimes, for example at Glastonbury Tor, the result is regular enough to give an impression of archaeological artifacts.
http://en.wikipedia.org/wiki/Terrace_%28agriculture%29
