Swales are an earthwork method designed to slow the flow of water and halt soil erosion. Yet, as Alfonso Chico de Guzmán explains, the benefits of swales go beyond protecting fertile soil. Making swales an essential component of resilient agriculture.
On the high plateau of the Altiplano Estepario, water is and always has been scarce. The landscape is a semi-arid steppe system; there’s just enough rain to prevent a desert ecosystem. When the rains do arrive they are often torrential. Combined with severe de-vegetation in the region, fast flowing water carries away fertile soil: in some areas, the land loses more than 25 tons of soil per hectare per year. Fertile soil is non-renewable and has to be re-created. Therefore, soil erosion is a major threat to agriculture in the Altiplano Estepario.
Alfonso Chico de Guzmán is a Spanish farmer working with AlVelAl. On his farm – La Junquera –Alfonso experiments with techniques to prevent soil erosion. Over the last five years, Alfonso has built more than 15km of swales: an earthwork technique used to slow the flow of water on steep slopes. In a recent episode of Farmerama, Alfonso explains, “I really like swales because they do a lot of services at the same time. The erosion control is the most obvious. But also the humidity they create around them is higher than the rest of the field. That combined with the sediments that they keep there, year over year it becomes a more fertile and humid line of soil”.
Swales are built by first measuring and marking along the contour of a slope. A tractor then drives with a blade to carve out a trench. A farmer can create several kilometres of swales in one day making this simple earthwork an effective strategy for slowing the flow of water and preventing soil erosion.
Alfonso plants trees and shrubs – like almonds, olives, rosemary and lavender – along the lower side of the swales. The roots hold the earthwork in place while taking advantage of the available humidity. When the swale settles and builds up humidity, the trees will be ideally placed. However, it may take some time. “At the beginning the trees suffer but they’ll be some of the better developed vegetation in the future”, says Alfonso.
The plants growing along swales make them critical wildlife corridors. Permanent strips of vegetation provide habitat for wildlife throughout the year. Which is important in fields of annual crops which are regularly cleared. “After you harvest grain, the fields are barren. These corridors are really useful for the birds to nest, but also for boars, the foxes and rabbits to cross the field”, describes Alfonso.
Techniques like swales are essential for farming in the Altiplano region. With the right knowledge, farmers can implement swales over large areas at low cost. Creating these earthworks across the landscape prevents soil erosion, establishes new areas for tree planting and provides habitat for biodiversity. Looking out across the Altiplano, it is easy to imagine swales snaking across fields, supporting a resilient agriculture that faces up to the challenges of the future.