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Poster Session 2
“Socio-economic imperatives”

Protection ratio, an economic indicator for assessing locations for
strategic dike reinforcement for erosion management in
rainfed paddy-upland sandy soil mini-watersheds

Caldwell, J.S.1; S. Sukchan2; C. Ogura3; W. On-Ok4 and M. Prabpan5


Farmers in Northeast Thailand manage mini-watershed ecosystems in which each farmer has rainfed paddies in valley bottoms and upland fields in sandy soils on sloping valley sides. Farmers grow glutinous rice in the paddies for home consumption and sugarcane and cassava in the uplands as cash crops. We chose one village, Nong Saeng, Khon Kaen Province, to develop a participatory research process to identify management needs and test rapid solutions. This resulted in an economic indicator, the protection ratio, for assessing locations for strategic dike reinforcement.

The process consisted of four steps: 1) farmer selection of mini-watershed transect locations for needs assessment; 2) presentation of technical options for solution of needs; 3) farmer selection of an option to adapt; 4) selection of test sites. Farmers proposed using magnesium oxide (MgO) for dike reinforcement at strategic breakage locations. Locations were chosen based on a dike breakage survey and a watershed model. Four sites were located between upland fields and the central paddy area.

The protection ratio calculated as area of paddy protected in rai (0.16 ha)/10 m2 reinforced dike was developed as an indicator of economic benefits. Economic costs were based on tractor rental to repair dikes annually and materials and labour costs of MgO reinforcement in the first year. Economic benefits were based on observed yields in protected and non-protected areas and projections over three rainfall scenarios. At site A with a protection ratio of 0.7 (2.1 rai protected by 31.1 m2 reinforced dike), net benefit of Bht 1,118 was realized only under the most favourable scenario of 1 dry year and 2 normal years. At site C with a protection ratio of 5.4 (9.7 rai protected by 17.9 m2 dike), positive economic benefit of Bht 5,468 was estimated over one dry, one wet, and one normal year.

1 Development Research Division, JIRCAS, JAPAN/THAILAND
2 Office of Soil Survey and Land Use Planning, LDD, THAILAND
3 Department of Agricultural Environment Engineering, NIRE, JAPAN; formerly JIRCAS, JAPAN/THAILAND
4 formerly Office of Soil Survey and Land Use Planning, LDD, THAILAND
5 Mitr Pohl Sugarcane Research Centre, THAILAND, formerly Office of Soil Survey and Land Use Planning, LDD, THAILAND

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