In agriculture, this process refers to the wearing away of a field’s topsoil by the natural physical forces of water and wind or through forces associated with farming activities such as tillage or livestock hooves.
Preventing Erosion in the Forest Garden
The topsoil in a Forest Garden is a critical component in maximizing and optimizing the productivity of a parcel of land. The more stable and fertile the topsoil, the healthier and more vigorous the growth of the Forest Garden plants. As a result, Forest Garden farmers adopt the following techniques to prevent that topsoil from being eroded away by water or wind.
Combating Water Erosion: There are many Forest Garden techniques that help prevent water erosion. The faster water falls onto or flows across the land, the more soil erosion there will be. Therefore the key is helping water to slow, spread across the land, and sink into the ground. Slowing is done through horizontal and vertical barriers. By having trees throughout the Forest Garden, their branches and leaves intercept rain drops and slow them before they drop onto the ground. Bare soil should always be protected from raindrop impact through mulching as well.
To slow and spread water, farmers practice contour planting in areas of steep slopes, where they create vegetative barriers that run perpendicular to the slope to prevent water from running off the hillside and carrying away topsoil and its nutrients. Even in land that seems flat, soil erosion can occur. Here, farmers might plant vegetative strips along the contour, but instead of planting with multiple lines of trees and other plants, they may just use one type of grass. The many tree systems throughout the Forest Garden, like Alley Cropping and the Green Wall, serve to stabilize soil and hold it in place through the network of tree roots. The ability of water to sink into the ground also has to do with soil quality, so all practices that work to improve soil texture through organic matter and fertility will lead to better water absorption and less erosion.
Combating Wind Erosion: Many people think about a windbreak’s purpose as preventing wind damage to crops, but another important function of the windbreak is protecting soil from erosion. Strong winds can blow topsoil off a field as dust. To mitigate the soil erosion from strong winds, farmers plant windbreaks along the side of the field that faces the strongest winds or multiple sides if the wind comes from different directions through the year. A windbreak can consist simply of one row of trees, but the most effective windbreaks have multiple, staggered rows with shorter shrubs and trees comprising the outer row and taller trees making up the second row. This will guide the wind up and over the field rather than through it. A windbreak can protect land up to 10 times the height of its tallest trees.