Soil erosion and conservation OBJECTIVES

Students should be able to define:

■ Soil erosion

■ Soil conservation

■ Outline ways to practice soil conservation in the Caribbean

Soil erosion is the process by which water or wind removes topsoil and its nutrients from the land. Exposed soils can be blown away by wind, and bare soils on slopes can be easily washed away as silt. Soil erosion is one of the factors which may have a negative impact on soil fertility. Therefore, to maintain soil fertility, it is important to prevent this form of erosion and practise good soil-conservation methods. When soil is cleared of vegetation and not covered to prevent soil erosion, its fertility decreases rapidly (Elliot, Wolsey, Barran et al, 2011). In the Caribbean, erosion is mainly by rainfall and surface water. The wind also causes erosion, especially during the hurricane season.

There are several factors that may cause soil erosion. These are:

1. Climate: Whenever it is mostly wet and windy.

2. Topography: Whenever the slope is steep, the rate of soil erosion is greater and more likely to occur.

3. Soil properties: Soils which allow water to penetrate faster, with more organic matter and improved soil structure, have a greater resistance to erosion.

4. Deforestation and overgrazing are other factors that cause soil erosion.

TYPES OF CONSERVATION

a. Erosion by water: Water is the most important agent of erosion. Water-related erosion is just one type of erosion. During erosion cause by water, the soil is washed away and carried off to a new place. For example, rivers and rain can both cause erosion. Rain won’t move dirt very far away, but rivers can carry it for miles and miles. Like all types of erosion, water-triggered erosion is a slow process that creates large changes over many years. Over time, the repeated movement of water can wash away soil and bring it to a new place. This can lead to huge changes in the Earth’s landscape.

b. Erosion by wind: Wind-originated erosion is a serious environmental problem attracting the attention of many across the globe. It is a common phenomenon occurring mostly in flat, bare areas; dry, sandy soils; or anywhere the soil is loose, dry, and finely granulated. Wind-induced erosion damages land and natural vegetation by removing soil from one place and depositing it in another. It causes soil loss, dryness and deterioration of soil structure, nutrient and productivity losses, and air pollution. Suspended dust/ dirt is inevitably deposited on everything. It blows on and inside homes, covers roads and highways, and smothers crops. Sediment transport and deposition are significant factors in the geological changes which occur on the land around us and over long periods of time, are important in the soil-formation process.

SOIL CONSERVATION

Soil conservation is the management of soil to maintain its nutrients, organic matter content and structure. Preventing soil erosion is a major part of soil conservation (Elliot, Wolsey, Barran et al, 2011). In the Caribbean, there is limited arable land, unfavourable soil types and insufficient flatland. There is also much competition between agriculture and housing for land use. Farmers within the region practise several methods of soil conservation. Each country, depending on its particular situation, may employ one or more of the following methods:

1. Terracing: Terrace farming is a type of farming that was invented by the Inca people who lived in the South American mountains. This farming method has made cultivation of crops in hilly or mountainous regions possible. It is commonly used in Asia by rice-growing countries such as Vietnam, Philippines, and Indonesia. As posited by worldatlas.com, terrace farming is a method of farming whereby ‘steps’, known as terraces, are built on to the slopes of hills and mountains. When it rains, instead of the rain carrying away the soil nutrients and plants down the slope, they flow to the next terrace. Every step has an outlet which channels water to the next step. This helps in keeping some areas dry and others wet. On very high altitudes, other crops apart from rice can be grown. This is because rice does not do well at high altitudes. There are two types of terracing: graded terracing and level terracing. A graded terrace may have either constant or variable grades along its length. On the contrary, the level terraces follow a contour line and are best suited for permeable soil.

2. Contours: This is where the gradient of the slope is used by farmers when planting. The rows are placed across the slope to act as barriers to prevent the flow of water downhill.

3. Other methods of soil conservation include afforestation and mulching.

This concludes this week’s lesson. I sincerely hope that the information provided was of great help.

Blessings to all.