Rice Planted area suitability in Thailand

Dr Supan Karnchanasutham
Director, GIS and Remote Sensing branch,
Ministry of Agriculture and Co-operatives
Bangkok, Thailand
[email protected]

Rice is the most important economic crop in terms of both domestic consumption and export. Thailand ranks first among the world rice exporters with an income of hundred million bahts. However, rice yield has still been as low as 60 kg / hectare. Especially when compared with rice yield of various countries, Thailand is among the lowest group. It is even lower than that of Laos, Myanmar, Indonesia and China. During 1961-1993, the annual declined in the rate of forest area was 0.44 million hectare. In 1988, forest concession was cancelled for the whole country. However, during 1989-1993 forest was encroached with the area of 0.99 million hectare or the average annual of decline rate of 0.24 million hectare. In 1993 the existing forest was therefore only 13.36 million hectare or 26% of the whole of the country area. In present times it is necessary to improve the yield because rice area cannot be expanded further into the forest. The Department of Agriculture has conducted relevant researches to improve rice yield rice variety, land fertility, pest control, etc. However, the yield has still not improved much due to the unsuitability of the area for rice cultivation. Neither physical nor economical conditions are suitable. GIS, the integration between spatial and attribute data, is therefore necessary for the allocation of suitable area for rice which will eventually lead to agro-economic zoning.

Objectives

• To produce maps of rice suitability area with respect to physical potential of the area.
• Maps thus produced will lead to agro-economic zoning.

Methodology

Data conversion
Data conversion from the existing map into digital format is done by compiling such maps from relevant agencies. In case some thematic maps are not available or are obsolete, then up-to-date maps will be produced by the Office of Agricultural Economics (OAE). The converted relevant maps include:

Watershed base map: It was obtained from the National Committee on Hydrology, NRCT. Watershed area means an area where the rainfall drain into. Watershed classification and nomination is undertaken based on the respective main stream except in the coastal area and the area near Cambodia border where main stream does not exist. Watershed classification and nomination of such watersheds is therefore based on geographical conditions such as eastern coast, western coast, eastern south, and western south.

Rice Planted area suitability in Thailand

Watershed area allocation is made by defining the derive from the topographic map of 1:50,000. Thailand comprises a total of 25 main watersheds, each of which includes 4 levels of stream 1) main stream 2) sub stream 3) perennial gully and 4) seasonal gully.

Provincial soil series map: Drawn at a scale of 1:100,000 or 1:50,000 is obtained from the Land Development Department (LDD), which comprises of 312 soil series for the whole country.

Irrigation map: It is obtained from the Royal Irrigation Department (RID) comprising both irrigation and non-irrigation zones.

Average rainfall map: It covers a period of 39 years from 1951 to 1989 and is obtained from the Department of Meteorology showing average rainfall ranging into 10 levels. They are:

• Rainfall of 1,000-1,100 mm.
• Rainfall of 1,100-1,200 mm.
• Rainfall of 1,200-1,400 mm.
• Rainfall of 1,400-1,600 mm.
• Rainfall of 1,600-2,000 mm.
• Rainfall of 2,000-2,400 mm.
• Rainfall of 2,400-2,800 mm.
• Rainfall of 2,800-3,200 mm.
• Rainfall of 3,200-4,400 mm.
• Rainfall of 4,400-5,000 mm.

Forest legal boundary map: It is drawn at a scale of 1:250,000 obtained from the Royal Forestry Department, which includes both inland forest and mangrove boundaries. Inland forest is categorized into two zones:

• Economic forest boundary
• Conserved forest boundary

Mangrove land use is categorised into the following zones:
Conservation zone represents the mangrove area prohibited for any change to conserve the environment and ecosystem. The zone includes 10 categories namely:

• Areas for the breeding of economic plants and aqua-animals.
• Areas for the breeding of plants and aqua-animals.
• Areas prone to destruction and soil erosion including beach, sand dune, mud flat, accreted mud flat, accreted sand, island, cave and coral reef.
• Areas of historical and archeological significance.
• Areas of local symbol.
• National park, forestry park, tourism spot, wildlife sanctuary, and hunting prohibited zone.
• Forest areas reserved for fire protection.
• Forest areas suitable for research.
• Forest areas suitable for environment and ecosystem conservation.
• Areas at a distance of not less than 20 meters from river banks and not less than 75 meters from coast lines.

Economic zone includes 2 categories namely:
(i) Economic zone A includes mangrove areas allowed for forestry activity especially to provide regular production. They are namely:

• Concessioned forest area and forest under project area.
• Unconcessioned forest area suitable for social forestry.
• Forest plantation area for forest products of both government and private sectors.

(ii) Economic zone B includes mangrove areas allowed for other land utilisation and development. However, environmental impacts are to be taken into consideration. The area includes:

• Agricultural area for the following purposes:
  • Crop cultivation
  • Livestock
  • Fisheries
  • Salt pan
• Industrial area
  • Mining
  • Industrial Factory
• Urban area
  • Commercial area
  • Sea port
  • Others

Road network map: Drawn at scales of 1:1,000,000 and 1:250,000 obtained from the Department of Highway and the Royal Thai Survey Department, includes:

• Road comprises:
  • Highway with number
  • Provincial road with number
  • Road under the Office of Accelerated Rural Development
  • Dirt road, and etc.
• Railway
• Road along irrigation canal

Administrative boundary map: Drawn at a scale of 1:250,000 obtained from the NSO, includes:

• Province boundary
• District boundary
• Sub-district boundary
• Locations of province, district and sub-district offices

The information obtained in 1997 comprises 76 provinces, 812 districts, 7,409 sub-district and 68,700 villages.

Present land use map: Drawn at a scale of 1:250,000 obtained from 1994 satellite image interpretation by OAE, includes the Catategories as mentioned in Table 1.

Data Analysis
It was carried out by using Intergraph GIS and Oracle softwares under Window NT operating system. The steps are as follows:

1) Project construction and database establishment to integrate spatial information, obtained from digital map, and attribute information so called topology.

2) Data analysis was undertaken by overlaying of multi-layer spatial information. The data includes:

• Soil series were categorised, in accordance with suitability condition, into 4 levels representing:
  • high suitability for rice cultivation
  • moderate suitability for rice cultivation
  • marginal suitability for rice cultivation
  • unsuitability for rice cultivation

Table 1. Land Use Zoning

The soil series of high suitability for rice are for examples : Klang, Hhao Yoi, Chacherngsao, Khok Krathiem, Chainat, Chai Badan, Chong Khae Chum Sang, Derm Bang, Damnoen Sa-duak, Tha Toom, Tha Rua, In-Buri, Nakhon Pathom, Nan, Bangkok, Bangkhaen, and Bang Nam Priew.

The soil series of moderate suitability for rice are for example; Khao Yai, Khlong Khood, Khok Khien, Chaliang Lab, Dong Lan, Tak Bai, The Khwang, Tha Sala, and Nakhon Phanom.

The soil series of marginal suitability for rice are for example; Kab Deng Kula Rong Hai, Chonburi, Chien Yai, Ton Sai, Thung Khai, Sai Khao, Na Khoo, Nam Kra Chai, and Bang Pa Kong.