Definition of the Technology:
Mai Sangphai (Bambusa oldhamii) planting technique for soil erosion control along river bank due to soil fixation by deep and widespread roots during rainy season when there are high water levels and increased flow velocity
During the rainy season when the rivers’ water levels are high and there is an increase in the velocity of the water flow, the Bambusa oldhamii (giant timber bamboo) has been especially selected to be grown along river banks because of its deep root system which effectively binds the soil thereby controlling soil erosion along river banks.
During the annual rainy season between July – October in Vangyang village (Phouvong district, Attapue province) the region experiences intense rainfall ranging from 2,500-3,000 mm/year (source: The Phouvong District Hydrology and Meteorology Office). Soil erosion occurs along riverbanks, with the end effect of gradually widening the river bed. It can be noted that the river banks in Vangyang village have already eroded by two meters which has resulted in the loss of agricultural land that was previously used to cultivate bananas and sugarcane. In order to counteract this development some of the land users initiated the planting Bambusa oldhamii on riverbanks in 2007. This strain of bamboo was selected because people could observe that the natural bamboo forest growing on opposite side of the river to their land experienced minimal soil erosion as the deep root system was able to successfully secure the soil along these stream banks. On top, Bambuse oldhamii has delicious shoots (which are consumed by land users) and less thorns compared to other wild bamboo species.
The application of this technology involves the following:
• The site should be selected along the stream banks especially where the risk of erosion is occurring. Bamboo should be planted approximately 3 meters from the edge of the bank. Bamboo is grown to protect the bank on one side of the stream from soil erosion whilst the other side of the stream is protected by natural bamboo species.
• Land preparation involves the clearance of bush around the planting pits.
• Bamboo rhizomes (Bambusa oldhamii) should be gathered locally from the parent plants. This should amount to approximately 120 healthy one-year old rhizomes each having a considerable number of feeder roots with a length of 60 to 70cm.
Forty holes measuring 50cm x 50cm and 50 cm depth should be dug in a row leaving a gap of 5 meters between each hole along the stream bank when the bamboo’s rhizome grow up it will be cover the gap for few meters from pits ( it will take about 4-5 years). After the land has been prepared 2-3 bamboo rhizomes should be replanted in each of the holes. The refilling of the holes with soil and watering should take about one day. Planting can be undertaken in January (dry season) because soil texture in dry season is less sensitive to erosion. This is a suitable time for bamboo as the roots will propagate faster. In the dry season watering needs to be done twice a week until the rhizomes establish new roots and stems. Generally, the bamboo will grow 4-5 new stems during the first year after having been replanted, but at this stage it is still unable to protect the banks from erosion. Some vegetation around the pits has been cleared before replanting and leave some vegetation on the edge to minimize erosion when the bamboo trees still young. When the bamboo is about 2-3 years old, it will be able to grow up to three times the amount of additional stems compared to its output in the first year. At this time the bamboo’s root system is able to expand more widely and deeply which helps to bind the soil and thereby it protects the stream banks from erosion during high water levels. (They left the bush and some vegetation on the edge of the stream, clearance of bush around the planting pits only) . Bamboo has multiple benefits: In fact, the older bamboo is able to provide a greater amount of protection and the bamboo shoots can either be consumed or sold by the land owners. Furthermore the bamboo culms can be used or sold for the manufacture of a variety of handicrafts. Bamboo enhances the micro-organisms habitat living in Rhizosphere (high biological activity and high nutrient availability) of the roots system and maintains the soil moisture throughout the year. The decaying bamboo leaves become a natural compost. The land owners are therefore very content and are willing to recommend the technology to their neighbors who also own land along the stream banks. The weaknesses: (1) Once the bamboo expands and grows into clumps it becomes the habitat of mosquitoes and snakes and thus weeding is required. (2) Bamboo leaves that have fallen into the water decay afterwards and deteriorate the water quality, and therefore it is recommended to cut back old branches before the leaves have the opportunity to fall into the stream.
Lao People's Democratic Republic
Region/ State/ Province: Phouvong District, Attapue Province
Further specification of location: Vangnhang Vaillage
Specify the spread of the Technology: applied at specific points/ concentrated on a small area
Comments: There are many bamboo trees in the forest along the stream but the land user who implements this technology is only in a single site in the village.
Source: LaoCAT, NAFRI, MAF