Khun Lean Hak
有助于对技术进行记录/评估的机构名称（如相关）Society for Community Development in Cambodia (SOFDEC) - 柬埔寨
有助于对技术进行记录/评估的机构名称（如相关）Local Agricultural Research and Extension Centre (LAREC) - 柬埔寨
Rice husks as well as empty seeds are pyrolised and used as a soil amendment in the rice seed beds and the vegetable gardens.
Biochar is the residue left after the pyrolysis of any organic matter and is used as a soil amendment. Pyrolysis occurs when the organic matter is heated in anaerobic conditions, which is usually done in specially designed kilns. Sometimes it is also made in a conventional fire, which is extinguished before the char turns to ash. Agricultural wastes like rice husks or unfilled grains are mainly used. Biochar can have many positive effects on the soil and plants:
-It buffers the pH, and has usually a high pH due to theash content.
-Due to its porous structure, it holds water and serves as refuge for microorganisms.
-It absorbs and adsorbs nutrients, both cations and anions. They are available for the plant roots.
-It can increase the resistance of plants to diseases.
Due to all these effects, the increased yields are higher than those that can be achieved only through the nutrients contained in the Biochar itself. Biochar is and was used in many parts of the world as soil amendment, with some benefits persisting for centuries. In Cambodia it was used during the Pol Pot regime to reduce the smell of the human faeces that were used on the fields due to a lack of other fertilizers. Today research in the Biochar domain is increasing, especially since the discovery of the man-made terra preta soils in South America.
Biochar is mainly used to increase the fertility, water holding capacity and carbon content of the soil. The fact that the benefits of Biochar addition to the soil remain for several years, unlike chemical fertilizers, makes it attractive to farmers. Other purposes, like the increased resistance of plants to diseases and buffering of nutrients are also of importance.
Biochar was introduced or reintroduced trough different NGOs, JICA (Japanese International Cooperation Agency) in this case study. Because of knowledge exchange between farmers, a rice husk char/ash mix, as residue from the pottery baking, was used already in 2011. In 2013 JICA borrowed a Biochar kiln to the local farmer self-help group with a training, so they could produce Biochar by themselves. The inner part of the kiln (cf. technical drawing) is filled with wood and lit. It is then put into an empty oil barrel, which is filled with rice husks. The heat pyrolyses the husks from the bottom to the top of the barrel, and the gases are burned in the inner part of the kiln and the chimney. Just before the upper part is pyrolysed, the husks are extinguished. There is a weight loss of about 50 to 60 % caused by this process. The Biochar is added to the fields after ploughing, and the fields are harrowed. In this case study, Biochar is used both in rice seed beds and in a vegetable patch. Concentrations of 0.5 kg/m2 are used in the rice seed bed, and 2.5 kg for the vegetables. Due to the little available quantities of husks, Biochar is not applied to the field yet. The use of Biochar is spreading quickly from farm to farm
The analysed area is flat (slope < 2%), with a tropical climate (dry season from November to May and wet season from June to October), and the soils are mostly sandy or loamy. The soil has a low fertility, contains little organic matter, and acidifies. The area has been deforested a long time ago, and the groundwater table is rather high (1-2 m during the dry season, on the surface during wet season).
Due to climate change, farmers notice more erratic rainfall, temperature rises and more recurrent droughts. Rice is the predominant crop grown in the area, since it serves as staple food (mix subsistence and commercial activities). Cattle are usually grazing on the fields after the harvest, without much control. Thus the cattle grazes too often and too much on the same spot, leading to degradation.
The increasing migration rate (the young generation leaves the villages to work in the cities, garment industry or abroad) results in a decrease of available labour force in the area which has detrimental effects on the agricultural activities. Furthermore, the civil war in the 1970s (Khmer Rouge) led to the loss of agricultural knowledge. Several NGOs are trying to re-establish the knowledge.
- 0.1-1 平方千米
Area unknown and rapidly spreading.
It was introduced in 2010 by JICA, the Japanese International Cooperation Agency.
年作 - 具体指明作物:
- 蔬菜 - 其他
- 蔬菜 - 叶菜（色拉、卷心菜、菠菜和其他）
- 蔬菜 - 根茎类蔬菜（胡萝卜、洋葱、甜菜等）
- 蔬菜 - 香瓜、南瓜、南瓜或葫芦
- rice, cucumber
Longest growing period in days: 210, Longest growing period from month to month: June-December
Major land use problems (compiler’s opinion): Soil fertility decline, water availability
Major land use problems (land users’ perception): Water availability. Interestingly the farmer says that soil fertility is not a problem, as the farmers know about the use of compost. The compost application is the problem.
Livestock is grazing on crop residues
In the vegetable patch the farmer plants cucumber, pumpkin, onion, watermelon and leaf vegetables in the early wet season, before planting rice.
Main causes of degradation: soil management (Ploughing and bare soil during dry season.), labour availability (Farmers go to work in the garment industry, in construction, or sell their labor elsewhere.)
Secondary causes of degradation: deforestation / removal of natural vegetation (incl. forest fires) (Deforestation happened many years ago.), overgrazing (Uncontrolled grazing during dry season.), change in temperature (More hot days according to UNDP and farmers.)
Biochar kiln. In the inner part, the combustion chamber, a wooden fire is lit. The burning chamber is then placed in the oil barrel, which is filled with rice husks. The heat pyrolyses the husks, the gas burn in the chamber and chimney. When pyrolysis is almost completed, the char is extinguished.
Technical knowledge required for field staff / advisors: high
Technical knowledge required for land users: moderate (When farmers only buy Biochar the required technical knowledge is low.)
Main technical functions: increase in organic matter, increase in nutrient availability (supply, recycling,…)
Secondary technical functions: improvement of surface structure (crusting, sealing), improvement of topsoil structure (compaction)
Manure / compost / residues
Material/ species: Rice husk Biochar (together with compost, which he already did before)
Quantity/ density: 0.5-2.5
Remarks: Entity: kg/m^2. Distributing on fields and harrowing.
Stefan Graf, Switzerland
|1.||Biochar making||Whenever there is time|
|2.||Adding Biochar to the fields after the compost was plowed in, and harrowing.||Yearly, before planting.|
The costs are indicated per unit; a unit is one biochar kiln used on 1 a. The costs were calculated in 2014 for the vegetable beds, where the farmer uses around 2.5 kg/m2. He also uses Biochar on the rice seedling bed, with concentrations of around 0.5 kg/m2, 5 times less than in the vegetable patch. In the vegetable patch the farmer plants cucumber, pumpkin, onion, watermelon and leaf vegetables in the early wet season, before planting rice.
The factors affecting the cost the most are the biochar kiln, and the amount of added Biochar.
- < 250毫米
- > 4,000毫米
1486.45 mm 2013 in Kampong Chhnang
Thermal climate class: tropics. 27° to 35°C
- 0-100 m a.s.l.
- 101-500 m a.s.l.
- 501-1,000 m a.s.l.
- 1,001-1,500 m a.s.l.
- 1,501-2,000 m a.s.l.
- 2,001-2,500 m a.s.l.
- 2,501-3,000 m a.s.l.
- 3,001-4,000 m a.s.l.
- > 4,000 m a.s.l.
- 非常深（> 120厘米）
Land users applying the Technology are mainly common / average land users
Population density: 10-50 persons/km2
Annual population growth: 0.5% - 1%
Off-farm income specification: handicraft, remittances and factory work
- < 0.5 公顷
- 0.5-1 公顷
- 1-2 公顷
- > 10,000公顷
Land users have a title that is not recognized by the state.
According to the farmer, 50 to 70 % yield increase on his vegetable patches.
Rice husks become a demanded product instead of a waste. On the other hand, less pesticides are needed.
Biochar has to be made and added to the fields.
Increased production, healthier plants/less pests.
Less pesticides needed.
contribution to human well-being
Increased income, less expenses on pesticides.
Plants can stand a short dry spell better if grown with Biochar.
A waste, rice husks, is returned to the soil. Biochar also adsorbs and absorbs nutrients.
The carbon from Biochar has a long half-life period in the soil .
Less pesticides needed.
The costs for the pyrolysis kiln were not borne by the land user. But as the farmer of this case study wants to build an own kiln as soon as the NGO needs it again, it is positive.
100% of land user families have adopted the Technology with external material support
100 land user families have adopted the Technology with external material support
Considering only the farmers applying the technology with this stove. Other farmers buy Biochar, or burn the rice husks and extinguish them. But those farmers are nearly impossible to quantify as it changes quickly. The support was the kiln, which is only a small part of the costs.
Considering only the farmers applying the technology with this stove. Other farmers buy Biochar, or burn the rice husks and extinguish them. But those farmers are nearly impossible to quantify as it changes quickly.
In another area of Cambodia where the Ministry of Agriculture, Forestry and Fisheries (MAFF) is doing Biochar research, there was such a strong adoption of Biochar use that there are no more control areas. In Kampong Chhnang, the use of Biochar starts to spread now.
|Less insect damages where Biochar is applied.|
|Good growth of vegetables, with increased yields especially for onions.|
|The rice seedlings are stronger, and the roots break less while transplanting, and the plants recover quickly.|
|The plants survive a short dry spell better.|
|Soil amendment with long-term effect, as Biochar has a long half-life period.|
|Buffering and raising of the pH, especially in sandy soils.|
|Less washing out of nutrients.|
|Substrate to make Biochar (rice husks) is difficult to find in the area in big amounts, as only small rice mills are working there.||
Rice husks are wasted in other places. Networking with other villages.
Use other (waste) sources of organic matter like leaves.
|Increased workload for the Biochar production (compensated by the increased yields).||Use a bigger kiln to decrease the workload.|
|The energy produced during the pyrolysis is wasted.||Use it to power engines or as heating source. This would only be viable on large-scale kilns.|