Soil improvement / Clay / Bentonite / Crop production / Vegetable growing / Yields / Thailand

International Water Management Institute (IWMI).

English

Research Papers in Economics

Improving soils and boosting 
yields in Thailand
Issue 2 - 2010
Healthy soil
IWMI researchers, in cooperation with Khon Kaen University and local farmers, succeeded in boosting crop yields with a simple soil 
improvement technique.
A key property of soil is its ability to provide nutrients and water to growing crops. Clays and organic matter are vital in this regard. However, 
it is often difficult to retain organic matter in tropical soils, so farmers need to routinely apply compost. Soils that contain high levels of 
particular clays such as smectites, are often very fertile. For example, smectite-rich clays on the Central Plains of Thailand are among the 
most productive in the world. As productivity declined in the farmlands of Northeast Thailand, which have soils 
with low clay contents, farmers sought to add material from clay-rich termite mounds to their soils. However, 
because of overexploitation this natural resource soon became scarce. 
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WaterM anagement
International
InstituteIssue 2 - 2010
It is often difficult to retain organic matter in tropical soils. 
Boosting soil productivity
Scientists conducting studies in Australia found that adding 
bentonite, one of the smectite family of clays, could help 
increase soil productivity by assisting in the retention of water 
and nutrients. Motivated by this work, IWMI researchers, in 
cooperation with Khon Kaen University and local farmers, 
conducted various trials in Northeast Thailand. The aim of one 
project was to assess the impacts of applying locally sourced 
bentonite to rice yields. Supplementing the farmer’s usual 
practice with a single application of 200 kg of bentonite per rai 
(6.26 rai = 1 ha) resulted in an average yield increase of 73%. 
This was despite the bentonite being of relatively poor quality. 
Further studies showed that applying locally sourced bentonite 
to degraded sandy soils also reduced the risk of crop failure 
during drought years. 
Taking the results of several such field trials on yields of forage 
sorghum, scientists recorded a sixfold increase in biomass 
production after applying bentonite and mixing it with the soil 
using a rotavator or disc plough. The researchers also 
demonstrated that the increased soil quality generated by a 
single application of clay persisted for at least 3 years. By 
tapping into existing farmer networks, they encouraged wider 
uptake of bentonite clay as a means of improving the soil 
condition. 
In 2008, 3 years after the initial trials, IWMI scientists conducted a 
survey among 250 farmers in Northeast Thailand, half of whom had 
conditioned their fields with clay and half who had not. The average 
output for the farmers using bentonite was 18% higher than for 
non-clay users. Using the clay had enabled some farmers to switch 
to growing vegetables, which require more fertile soil. Because the 
value of vegetable crops is much higher than staples such as 
cassava, these farmers earned more on-farm income as a result. 
The researchers estimated that some 200 farmers in Northeast 
Thailand and 400 in neighboring Cambodia had adopted the use of 
clays, and that a further 20,000 farmers were introduced to the new 
technique. 
A new industry
Thailand’s Land Development Department (LDD) has subsequently 
developed a product, called LDD10, combining waste bentonite 
from the vegetable oil industry with organic material. This is cheaper 
than applying pure clay but equally effective. The LDD is producing 
around 1,000 tonnes of this material annually. Farmers can obtain it 
for free but have to cover the costs of transporting it to their land. 
IWMI’s work has also generated interest elsewhere. Bentonite has 
traditionally been used as an industrial mineral. Now, producers in 
South Africa are conducting trials with the aim of developing a 
product to be marketed as a soil improver. Meanwhile, a large 
bentonite producer in Australia has been conducting trials on the 
island of Nauru to see if clay can effectively rehabilitate soils 
following mining for phosphorus. 
Donors and collaboratorrs
IWMI worked with Khon Kaen University, the Land Development 
Department of the Royal Thai Government and Australia’s 
Commonwealth Scientific and Industrial Research Organisation 
(CSIRO) during its bentonite soil-improvement project in Northeast 
Thailand. The Australian Centre for International Agricultural 
Research (ACIAR) provided funding support to partners. 
For more information
IWMI report: 
www.iwmi.org/Research_Impacts/Impact_Assessment/Outcome_St
ories/2008/Bentonite%20clays-%20edited%20outcome%20story_fin
al%20_Web_.pdf
Improving the management of land and water resources for food, livelihoods and the environment 
All IWMI Publications are available online free of charge at www.iwmi.org/Publications
Comments and questions are welcome. Please contact us at: IWMI-Publications@cgiar.org
Publications Unit, International Water Management Institute, PO Box 2075, Colombo, Sri Lanka
Tel: +94 11 2880000 Fax: +94 11 2786854
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WaterM anagement
International
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Improving soils and boosting yields in Thailand

http://www.iwmi.cgiar.org/Publications/Success_Stories/PDF/2010/Issue%202%20-%20Improving_soils_and_boosting_yields_in_Thailand.pdf

Improving soils and boosting yields in Thailand

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