MIRACLE CLAY
Poor soil is a serious problem facing farmers in the developing world. Years of intensive farming have led to soil degradation, reducing crop fertility. Researchers in Thailand are exploring a new approach to rejuvenating soils by using bentonite clays
Soil Degradation
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Soil degradation occurs when the primary vegetation, such as original forestry cover, is removed and replaced by secondary vegetation such as commercial crops. This replacement modifies the humus composition and amount, and impacts the formation of the soil. In parts of South East Asian region as much as 80% of primary forest has been destroyed leaving soil unprotected from natural erosion from rain and sun. Intensive crops such as sugarcane and cassava have exhausted the fertility of the soil so that now levels of humus, the fertile layer of soil, have been severely reduced. Now, due to the loss of organic matter, the soil has low nutrient capacity, low structural stability and low water holding capacity.
Although chemical fertilisers are available they are expensive, damaging to the environment and do not address the problems of soil rejuvenation. This unsustainable production pattern is contributing to the growing pressure on food security. |
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Reversing Soil Degradation
In Thailand researchers from the International Water Management Institute (IWMI) supported by the Consultative Group on International Agricultural Research (CGIAR) and Thailand 's Khon Kaen University are exploring new approaches that combat and reverse soil degradation using bentonite clays that rejuvenate the soil.
Bentonite is an absorptive clay consisting of extremely fine, microscopic particles of rock. In these trials bentonite from weathered volcanic ash is used as it has a particularly high mineral content along with a high amount of organic carbon. In Thailand bentonite is cheap as it is widely available in the central plains. Once collected it is mixed with rice husks and chicken manure on a one-to-one basis to form a compost that is then spread over the fields.
This practice provides an alternative method to one that is currently being used to treat soils with material from termite mounds or material dredged from reservoirs. Although this does improve the soils, this material is scarce and, in the long-term, unsustainable. To improve the soil through termite material requires a usage rate of 5,000 tonnes per hectare, whilst usage rates for the bentonite mixture is only 10-20 tonnes per hectare. The mixture provides all the attributes of a good growing medium - high levels of nutrients, an ability to retain moisture, and assist in the improvement to the soil structure.
Miracle Clay
Research has shown that yields of organic rice increased dramatically when organic composts and clay-based materials were introduced. Controlled trials have compared results from plots treated with dredged materials, bentonite and an untreated control plot. These clearly indicate bentonite treated areas are more productive. A group of 87 farmers, who are participating in these trials, share their results with other farmers across Thailand . Around 200 farmer families in 200 villages in Northeast Thailand are now using clay-based materials, indicating that approximately 20,000 farmers are aware of this practice.
Knowledge about this technology is spreading. In Cambodia , some 400 households are using clay-based technologies, while in Vietnam , IWMI was approached by the South Vietnam Department of Agriculture for advice on the use of bentonites. Estimates show that approximately 900,000 hectares in South Vietnam could benefit from this technology. The Northeast Thailand 's Land Development Department (LDD) has adopted the clay-based approach that includes the use of co-composted bentonite technology.
Bentonite offers an environmentally friendly and sustainable option for increasing soil productivity. Farmers, having seen the impressive results, are willing to adopt this innovative technology as they recognize the potential of adding clays to soils. Bentonite is now being made available commercially, as a product called LDD 10 and will be promoted in this region.
Further Information
