Best practices in sustainable land management

A soil bund is a structural measure with an embankment of soil or stones, or soil and stones, constructed along the contour and stabilized with vegetative measures, such as grass and fodder trees. The height of the bunds depends on the availability of stones. Bunds reduce the velocity of runoff and soil erosion, retain water behind the bund and support water infiltration. It further helps in ground water recharging.

Earth-banked terraces are constructed by carefully removing a superficial soil layer from one part of a field, concentrating it on the lower end of that field in order to reduce slope gradient and length. Another terrace is created directly downslope to form a cascade of terraces. The earth-banked terraces reduce flooding, damage to infrastructure and siltation of water reservoirs, while maintaining (or slightly increasing) crop productivity. This is achieved by reducing runoff, soil erosion and hydraulic connectivity through a decreased slope gradient and increased vegetation cover. The use of stones from the fields to reinforce the terraces is optional, but facilitates crop production in the fields and makes the ridges more resistant to higher runoff velocities. The technology requires an initial investment in the construction of the terraces.

Stone lines are constructed along the contours to slow down the speed of runoff, reduce soil erosion, and enhance water infiltration. In addition, the stone barrier blocks and settles down the sediments transported from the upper slopes. Stone constructions are often used to rehabilitate eroded and abandoned land.

Rockwall terracing refers to the piling of stones or rocks along contour lines to reduce soil erosion in hilly areas. Terraces are built to reduce soil erosion and ease land preparation through the removal of naturally-present rocks in the cultivated area. It also contributes to the partial arrangement and diversification of land use. The technology is a traditional practice in the Philippines.

Reshaping unproductive land into a series of levelled, gently-sloping platforms to create conditions suitable for cultivation and prevent accelerated erosion. Terrace construction was identified as an effective measure in degraded watershed areas to control runoff and decrease [the effects of] flash floods, increase water infiltration, and create opportunities for income from crop cultivation in the terraces.

Semi-circular bunds are used to rehabilitate degraded, denuded and hardened land for crop growing, grazing or forestry. The technology involves building low embankments with compacted earth or stones in the form of a semi-circle with the opening perpendicular to the flow of water and arranged in staggered rows. They are constructed on gently to moderately sloping pediments and plateau areas in order to rehabilitate areas that are degraded, denuded and/or affected by soil crusting. The bunds reduce the loss of water and the fertile layers of the soil.

Bench terraces are progressively expanded to form a fully developed terrace system in order to reduce runoff and soil erosion on medium- to high- angled loess slopes. The technology is mainly applied to tree plantations. Soil from the upper parts of the slope is removed and deposited below in order to extend the flat terrain. Over 5-10 years, the terraces become enlarged around each tree and form a terrace with the neighbouring trees along the contour, such that the slopes are transformed into level bench terraces. The trees are located in the middle of the terrace. All the work is done manually using shovels.

Belts of trees, planted in a rectangular grid pattern or in strips within, and on the periphery of, farmland to act as windbreaks. Shelterbelts are a specific type of agroforestry system that help reduce natural hazards including sandstorms, wind erosion, shifting sand, droughts and frost. They also improve the microclimate (reduced temperature, wind speed, soil water loss and excessive wind-induced transpiration) and create more favourable conditions for crop production. The establishment of shelterbelts plays a crucial role in the sandy drylands that are affected by wind and resultant desertification.

Strips of land are marked out on the contour and left un-ploughed in order to form permanent, cross-slope barriers of naturally established grasses and herbs. Natural vegetative strips constitute a low-cost technique because no planting material is required and only minimal labour is necessary for establishment and maintenance. Land users appreciate it because it effectively controls soil erosion and prevents loss of fertilizers.

Tree planting and establishment of grass strips along the river to stabilize steep slopes. The vegetation prevents surface water and eroded soil flowing from the agricultural fields directly into the river. Surface water flow from runoff during heavy storms is slowed down and infiltration on soils covered by grass and trees is increased. Therefore, sediments and chemicals used on the field are retained in the riparian soils and do not pollute the river. As a result more groundwater is recharged during the wet seasons, which can be released during the dry season. Damage during flood flows on the riverbank (through erosion and destabilizing the riparian vegetation) as well as damages of floods downstream can be reduced or avoided.