Applied to all areas with a slope greater than 30 degrees, specifically the face of Sand Hill.
As we approach what appears to be the the highest point on the property, the road starts working its way up Sand Hill. The edges of this hill have been sculpted into a series of densely planted terraces and slopes. I would have never guessed that this was the location of a sand quarry because all around us are lush plantings of native forest species. The birds are singing, the wind is rustling in the tree tops, and the occasional Green Monkey is even seen jumping from limb to limb.
- To stabilize the slope and reduce erosion.
- To establish native forest species to support the viability of sensitive and endangered natives on the island of Barbados and provide a habitat for native fauna.
- Because of the nature of the terrain and the requirements of the government to keep the hill at a certain height, we were unable to grade the slope down to a more gradual grade.
- The slopes have been engineered to a stable form to prevent landslides, but erosion can be rampant without the property design.
- The slopes are far too steep for people to regularly harvest, maintain or build.
- The sandy nature of the current soil makes precise sculpting nearly impossible as the wind can reshape any precision within hours.
- Using successive and dense plantings of deep-rooted vetiver grass (Chrysopogon zizanioides), fast-growing legumes and native-forest species, to quickly cover and protect the soil from erosion.
- The area will be planted up in native forest, including endangered species, so as to support the long term genetics of the Bajan forests and to provide a habitat for native fauna.
- These areas are also quite difficult to work on, and thus the planting patterns suggested for such an area will require minimal long-term maintenance.
- Generally, being above available catchment ponds will cause there to be little access to irrigation.
- Slopes in excess of 18 degrees are not suitable for most forms of earthworks, including swales and dams, so infiltration will need to be encouraged through the dense plantings of on-contour vetiver (Chrysopogon zizanioides) and living stakes.
- Over time, water filtration should increase as the forest develops and builds more organic matter.
There is a multiple phase plan for the planting of the site, and two distinct parts – steep slopes and terraces.
- Steep Slopes
- In the first phase of planting, vetiver grass (Chrysopogon zizanioides) will be densely planted on contour, every two feet of elevation.
- Between every other row of vetiver, we will plant quick stick (Gliricidia sepium), leucaena (Leucaena spp.), pigeon pea (Cajanus cajan) and other fast growing species to set shade and start the long-term process of fixing nitrogen. They will also provide a medium-term source for chop and drop mulch.
- After the pioneer species plantings have established themselves, we will come back in and plant the native forest species on the rows not yet planted.
- Terraces should be planted densely and quickly to reduce the fast-acting effects of wind erosion. Broadcast grass seed over the whole area directly following the earthworks on site (this would ideally be at the beginning of the rainy season).
- Plant legume trees of leucaena (Leacaena spp.), gliricidia (Gliricidia sepium), mothers tongue (Albizia lebbeck) and pigeon pea (Cajanus cajan) on six foot spacing throughout.
- At the beginning of the following rainy season, when the legumes have established themselves and started to create shade and a small amount of wind protection, move forward with the planting of native forest species.
- Plant these trees on a 10 ft spacing (more densely than often recommended), as we would rather have to chop and drop some down rather than have to come in later for replanting.
- As the extraction process wraps up in these planting plots, the terraces and slopes will be carved into the hillside.
- When and where possible, these terraces should be constructed slightly off contour so that excess water can over time be directed into catchment dams.
- The terraces should be tipped slightly back, into the hill, to reduce the amount of water flowing over the edge and resulting in erosion.
Phases of Development
- After the extraction of sand is complete, the earthworks are then to be completed.
- As soon as the earthworks are completed, there is a multiple phase plan for the planting of the site. See the planting section above.
- The idea with this area is that a minimal amount of long-term maintenance should be needed. In the interim however, there may be the need for some maintenance to get to the desired long term native forest.
- The legume species’ should be chopped and dropped onto contour two or three times each rainy season, until the native species have started to dominate the zone.
- When the natives have started to take over, the legumes should be cut back to their base and laid down on contour. This should be repeated once a year until their growth is clearly no competition for the natives.
- Application of compost tea, at least, quarterly for the first five years. Most important time is the beginning of the rainy season.