Water flow around Terra Preta raised garden beds, limiting erosion and facilitating infiltration of water (Karl Harald Bier)
One of the major problems in the mountainous rural zones of the municipality of Léogâne in Haiti is the severe degradation and erosion of soils. The soil loss aggravates the vulnerable situation of the local population, mainly farmers. The Terra Preta raised garden beds were introduced in this region after the earthquake of 2010, and were replicated by several organisations and also by members of the communities. They are based on two main techniques:
1) Terra Preta is a technique to create soils based on a lacto-acidic fermentation of organic matter with charcoal powder. This technique was used by indigenous people in Amazonia, and rediscovered and replicated recently by scientists. The technique is characterised by the use of local resources and a high fertility. With this technique, a soil layer of several decimeters can be produced in a few years, whereas this takes normally around 100 years per centimeter. Soil analyses show that the formation of humic acids can be demonstrated after 4 months.
2) Raised garden beds (Hugelculture) are a technique from permaculture. Permaculture is a science of agricultural and social systems which uses the principles of ecology and the knowledge of traditional societies to simulate the diversity, stability and the resilience of natural ecosystems. Raised garden beds consist of an interior of ligneous material, covered by a layer of earth. The elevated construction facilitates the work in the garden and the decomposition of wood inside the beds. Due to their spongy structure, the raised garden beds function as a water reservoir during dry periods.
The garden beds are placed perpendicularly to the slope direction as much as possible, and are arranged alternately, with an extension to redirect the surface runoff towards the structures. This arrangement prevents the water from draining directly. This promotes the infiltration of water into the soil, where it is captured by the ligneous material, which prevents erosion (see the photograph).
The following inputs to the garden beds can be found locally:
- Organic matter: ligneous material, dry straw, fresh straw, harvest residues, organic residues rich in NPK (kitchen waste, animal waste, etc.),
- Charcoal powder (biochar),
- Possibly ashes or other fertile materials.
With these materials, which are generally without cost and locally available, a raised garden bed can be set up in less than an hour. Even without additional fertilisation after the set up, the technique offers the possibility to have several cycles of vegetable production. Experiments showed good results during 4 years of continuous plantation in Thozin (Grand Goâve). In order to secure soil fertility for many years, organic matter can be added after the period of plantation. It can be easily incorporated below the first layer of soil, and the decomposition takes place automatically. When put in place on sloping terrain, the garden beds slow down erosion strongly, and can serve to protect houses.
The technique is valued because of its cost-effectiveness and its sustainability compared to known techniques. The complexity of the implementation can be a limiting factor for an autonomous replication by the beneficiaries. That is when they see the set-up of the structures and think they know how to replicate it without taking account of all the details which are essential for the good functioning of the structures. This is why generally a certain level of support by technicians is required.
ទីតាំង: Municipality of Léogâne, West department, ប្រទេសហៃទី
ចំនួនទីកន្លែងបច្ចេកទេស ដែលវិភាគ: 10-100 កន្លែង
ការសាយភាយនៃបច្ចេកទេស: អនុវត្តនៅកន្លែងជាក់លាក់មួយ/ ប្រមូលផ្តុំនៅតំបន់តូចៗ
តើស្ថិតក្នុងតំបន់ការពារអចិន្ត្រៃយ៍?:
កាលបរិច្ឆេទនៃការអនុវត្ត: តិចជាង 10ឆ្នាំមុន (ថ្មី)
ប្រភេទនៃការណែនាំឱ្យអនុវត្តន៍៖
| បញ្ជាក់ពីធាតុចូល | ឯកតា | បរិមាណ | ថ្លៃដើមក្នុងមួយឯកតា (Haiti Gourde) | ថ្លៃធាតុចូលសរុប (Haiti Gourde) | % នៃថ្លៃដើមដែលចំណាយដោយអ្នកប្រើប្រាស់ដី |
| កម្លាំងពលកម្ម | |||||
| Skilled labour (technical support) | person-days | 0,5 | 3000,0 | 1500,0 | |
| Unskilled labour (construction) | person-days | 1,0 | 250,0 | 250,0 | 100,0 |
| សម្ភារៈ | |||||
| Tools (spade, pickaxe) | piece | 1,0 | 5,0 | 5,0 | 100,0 |
| សម្ភារៈដាំដុះ | |||||
| Seedlings of cabbage | seedling | 10,0 | 10,0 | 100,0 | |
| Seedlings of spinach | seedling | 20,0 | 5,0 | 100,0 | |
| Seedlings of tomato | seedling | 10,0 | 5,0 | 50,0 | |
| សម្ភារៈសាងសង់ | |||||
| Decomposing wood | batch | 1,0 | 200,0 | 200,0 | 100,0 |
| Earth | batch | 1,0 | 50,0 | 50,0 | 100,0 |
| Dry straw | batch | 1,0 | 100,0 | 100,0 | 100,0 |
| Fresh straw | batch | 1,0 | 100,0 | 100,0 | 100,0 |
| Animal waste | Bag | 1,0 | 100,0 | 100,0 | 100,0 |
| Charcoal/biochar | kg | 50,0 | 2,0 | 100,0 | 100,0 |
| ថ្លៃដើមសរុបក្នុងការបង្កើតបច្ចេកទេស | 2'655.0 | ||||
| ថ្លៃដើមសរុបក្នុងការបង្កើតបច្ចេកទេសគិតជាដុល្លារ | 39.04 | ||||
| បញ្ជាក់ពីធាតុចូល | ឯកតា | បរិមាណ | ថ្លៃដើមក្នុងមួយឯកតា (Haiti Gourde) | ថ្លៃធាតុចូលសរុប (Haiti Gourde) | % នៃថ្លៃដើមដែលចំណាយដោយអ្នកប្រើប្រាស់ដី |
| កម្លាំងពលកម្ម | |||||
| Annual maintenance | person-days | 15,0 | 250,0 | 3750,0 | 100,0 |
| សម្ភារៈ | |||||
| Watering device | piece | 1,0 | 150,0 | 150,0 | 100,0 |
| សម្ភារៈដាំដុះ | |||||
| Seed and seedlings | various | 1,0 | 250,0 | 250,0 | 100,0 |
| ថ្លៃដើមសរុបសម្រាប់ការថែទាំដំណាំតាមបច្ចេកទេស | 4'150.0 | ||||
| ថ្លៃដើមសរុបសម្រាប់ការថែទាំដំណាំតាមបច្ចេកទេសគិតជាដុល្លារ | 61.03 | ||||
គុណភាពមុន SLM: None
គុណភាពក្រោយ SLM: an increase of yields by 2-3 times
The yield usually increases 2-3 times with the introduction of the technique.
The crops are more healthy and more resistant to diseases. The quality of the vegetables is better, and clients on the market of Grand Goâve pay more for the products from Terra Preta.
The majority of persons in the area are not used to vegetable growing. The technique makes it possible to grow vegetables which increase the nutritional basis (rice, pearl millet, sweet potato and peas).
Normally, the soils are not used for crop production. Through the technique production area is created. In addition, the surface increases through the undulated shape of the garden beds.
a) The infiltration of water in the soil is facilitated.
b) The water is retained by the organic matter in the garden beds (especially by the decomposing wood).
Water erosion is slowed down by the garden beds, and the sediments are deposited in front of these. However, the size of the garden beds is limited, and in order to combat erosion on a larger scale additional measures must be considered, like vegetated barriers or terracing.
Soil analyses
sample 1: 0.93%- >3.50%
sample 2: 2.04% - >5.51%
In the dry periods, the technique permits to continue crop production during several weeks without irrigation.
Sequestered in the soil by the charcoal and the organic matter (especially the ligneous material).
