Soil is the most fundamental and basic natural resource for all life to survive. Soil degradation is a major threat to the Earth’s ability and capacity to feed itself, about 40% of the world’s arable land is seriously degraded. One of the major causes of soil loss and soil degradation is erosion. Erosion is the wearing away of the topsoil by natural physical forces of water and wind. The process of erosion can be relatively unnoticed or can be at an alarming rate causing serious loss of topsoil.
Soil conservation has a long tradition in Sub-Sahara Africa as indigenous techniques like ridging, mulching, planting trees among others are employed to control soil erosion. It is, therefore, the act of preventing and reducing the amount of soil lost through erosion. Soil conservation tends to increase the amount of water infiltration in the soil while reducing the speed and amount of water run-off. Inappropriate land use act often causes changes in soil condition, which in turn contribute to soil erosion. The process of creating optimum conditions for plant growth through improved soil fertility and structure is called soil management.
Terraces belong to the type of soil management practices that aim to protect an area against runoff by systematic land planning. They are “steps” that are built into the side of a mountain or hill. On each level, various crops are planted. When it rains, instead of washing away all of the nutrients in the soil, the nutrients are carried down to the next level. Additionally, these steps prevent a free-flowing avalanche of water that would take plants with it and destroy all of the crops on the hillside.
Terracing is a soil conservation practice applied to prevent rainfall-runoff on sloping land from accumulating and causing serious erosion. It is the prevention and reduction of the amount of soil loss through erosion. It seeks to increase the amount of water seeping into the soil, reducing the speed and amount of water running off. Erosion is prevented by keeping enough vegetation to protect the soil surface, bind the soil together and maintain soil structure.
It allows better plant growth, which in turn provide larger plant canopy intercepting the falling rain from hitting the ground, dispersing the soil particles and increased proliferation of roots thus greater soil binding by the root system.
The efficiency of a terrace system increases by applying additional conservation practices such as appropriate land preparation (contour ploughing and sowing), appropriate cultivation of crops (e.g. strip cropping) and maintaining a permanent soil cover.
A very important point regarding terraces or any soil and water conservation practice is that most farmers are more concerned with production than with conservation. Therefore, the challenge is to develop conservation practices that are also productive. However, high labor intensity, time-consuming regular inspections, high consumption of scarce farmland, and the large amounts of construction material required are factors that stop farmers from installing or maintaining terraces.
It may be concluded that terraces could considerably reduce soil loss due to water erosion if they are well planned, correctly constructed and properly maintained. There are many examples showing that terraces have to be maintained to prevent processes leading to land degradation such as excessive soil erosion, gully formation and landsliding.