* Agronomist, Rice Research Institute, Department of Agriculture, Bangkok 10900, Thailand1. INTRODUCTION
Rice is the most important food crop in Thailand. The total area under rice is estimated to be about 11 million ha representing approximately 40 percent of the cropped land area. Rice lands can be classified as irrigated, rainfed lowland, deepwater, and upland ecosystems. More than 80 percent of the rice growing area in Thailand is under rainfed conditions where rice is usually grown only once a year in the wet season, where the monsoon rain is the single source of water supply for rice cultivation. Less than 20 percent of the area is under irrigated conditions where rice can be grown not only in the wet season but also in the dry season because irrigation water supply is available. In the 1997/98 crop year, the wet season rice accounted for 88 percent of the annual rice area and 80 percent of production. Dry season rice accounts for 12 percent of the area and 20 percent of production. Rainfed lowlands account for approximately 75 percent of the wet season rice area, and 68 percent of production. Deepwater and uplands account for a further 1.92 and 0.58 percent of the wet season rice area, and about 1.17 and 0.32 percent of production, respectively. Annual production in 1997/98 crop year was about 23.580 million tonnes. Some 18.789 million tonnes representing approximately 80 percent of the annual production is produced in the wet season when average yield is very low, at around 2.24 t/ha. Only 4.791 million tonnes representing approximately 20 percent of the annual production is produced in the dry season when average yield is relatively high, in the range of about 4.31 t/ha.
The general policy for rice production in Thailand is to produce rice for self-sufficiency and surplus for export to earn foreign exchange. Currently, it aims to produce about 22-23 million tonnes of paddy annually comprising 13-14 million tonnes for domestic consumption and about 8-9 million tonnes of paddy, which is equivalent to 5.5 million tonnes of milled rice, for export. Major production comes from the wet season rice crop with the supplement of the dry season crop.
2. STATUS OF RICE CULTIVATION IN DIFFERENT ECOLOGIES
2.1 National Rice Production Status
The area planted to rice in Thailand showed an increasing trend from the 1960’s to the 1980’s with approximately 2 percent growth rate, which leveled off in the 1990’s. The annual rice cultivated area in the 1960’s, 1970’s, 1980’s and 1990’s was about 6.698, 8.468, 9.932, and 9.865 million ha, respectively. Average yield and total production showed an increasing trend from the 1960’s to the 1990’s with approximately 1.70 and 3.01 percent growth rate, due mainly to an increase in irrigated and dry season rice production. Average yield in the 1960’s, 1970’s, 1980’s and 1990’s was about 1.57, 1.91, 2.02, and 2.28 t/ha with annual production of about 9.942, 14.625, 19.090, and 20.62 million tonnes, respectively.
The wet season rice growing area in Thailand showed an increasing trend from the 1960’s to the 1980’s with approximately 2.2 percent growth rate, and tended to decrease in the 1990’s. The average wet season rice cultivated area in the 1960’s, 1970’s, 1980’s and 1990’s was 6.698, 8.171, 9.212, and 9.077 million ha, respectively. The wet season rice yield showed an increasing trend from the 1960’s to the 1990’s with approximately 1.25 percent growth rate. The average wet season rice yield in the 1960’s, 1970’s, 1980’s and 1990’s was 1.57, 1.71, 1.90, and 2.07 t/ha, respectively. The wet season rice production showed an increasing trend from the 1960’s to the 1990’s with approximately 3 percent growth during the 1960’s-1980’s and 1.5 percent in the 1990’s. The average wet season rice production in the 1960’s, 1970’s, 1980’s and 1990’s was 9.942, 13.678, 16.693, and 17.370 million tonnes, respectively.
The extensive dry season rice production programme in Thailand began in the 1970’s. Cultivated area, yield and production of dry season rice exhibited an increasing trend. In the 1970’s, 1980’s, and 1990’s the area planted to dry season rice was 0.371, 0.678, and 0.781 million ha, with average yields of 3.31, 3.61, and 4.23 t/ha, resulting in dry season rice production of 1.417, 2.397, and 3.291 million tonnes, respectively.
2.2 Area, Production and Yield Trends in Different Ecologies
As mentioned earlier, rice production in Thailand can be classified into 4 ecosystems; irrigated, rainfed lowland, deepwater, and upland. Rainfed lowland is the most predominant rice ecology in Thailand followed by irrigated, deepwater and upland. There is no data available to compare the production classified by different ecologies. In a survey conducted by the Monitoring and Evaluation Section, Rice Research Institute, about 96.7, 2.9, and 0.4 percent of rice cultivated areas in the 1987/88 crop year were planted with lowland, deepwater, and upland rice varieties (Rice Research Institute, 1993) where about 15 percent of lowland areas were irrigated. IRRI (1993) reported that the area under rainfed lowland, irrigated, flood prone, and upland ecosystems in Thailand for the 1991/92 crop year was 8.756, 0.720, 0.660, and 0.053 million ha representing 78.6, 14.4, 6.6, and 0.4 percent of the total rice area, respectively. During the 1991/92 cropping year, the yield contribution to the total rice production of the country from rainfed lowland, irrigated, deepwater, and upland ecosystems was 15.760, 2.880, 1.320, and 0.080 million tonnes, or 78.7, 14.4, 6.5, and 0.4 percent of the total rice production, respectively. Average yield was highest in irrigated, followed by flood prone, rainfed lowland, and upland ecosystems, at about 4.0, 2.0, 1.8, and 1.5 t/ha, respectively (IRRI, 1993). There was no significant change in the area under the rainfed lowland environment, but the area under irrigation increased while areas under deepwater and upland ecosystems decreased significantly during the past two decades (Table 1).
Table 1. Estimated Harvested Area, Yield, and Rice Production in Thailand in 1977/78 and 1997/98 Crop year by Ecologies
|
Ecologies |
Area (million ha) |
Yield (t/ha) |
Production |
|||
|
1977/78 |
1997/98 |
1977/78 |
1997/98 |
1977/78 |
1997/98 |
|
|
Wet Season |
||||||
|
Irrigated |
0.705 |
1.905 |
3.01 |
3.55 |
2.120 |
6.761 |
|
Rainfed lowland |
6.474 |
6.223 |
1.30 |
1.87 |
8.420 |
11.632 |
|
Deepwater |
0.810 |
0.160 |
1.78 |
1.95 |
1.442 |
0.312 |
|
Upland |
0.300 |
0.048 |
1.31 |
1.75 |
0.393 |
0.084 |
|
Wet Season Rice |
8.289 |
8.336 |
1.49 |
2.25 |
12.375 |
18.789 |
|
Dry Season |
||||||
|
Irrigated |
0.461 |
1.112 |
3.45 |
4.31 |
1.586 |
4.791 |
|
Dry Season Rice |
0.461 |
1.112 |
3.45 |
4.31 |
1.586 |
4.791 |
|
Annual |
8.750 |
9.448 |
1.59 |
2.50 |
13.921 |
23.580 |
Irrigated: The irrigated ecology is the most favourable environment for rice production. The importance of the irrigated ecosystem to rice production in Thailand has two aspects: increased rice production in the wet season and in the dry season. In the 1977/78 crop year, the irrigated ecosystem accounted for about 13 percent of the annual rice cultivated area (0.705 million ha in the wet season and 0.461 million ha in the dry season) and 17 percent of production (2.120 million tonnes in wet season and 1.586 million tonnes in dry season). In the 1997/98 crop year, the irrigated ecosystem accounted for about 32 percent of the area (1.905 million ha in the wet season and 1.112 million ha in the dry season) and 49 percent of production (6.761 million tonnes in wet season and 4.791 million tonnes in the dry season). The average yield of irrigated rice was 4.31 t/ha in the dry season and 3.55 t/ha in the wet season, which is about 90 percent higher than rainfed lowland rice (Table 1).
Deepwater: Vast rice growing areas in the Central Plain of Thailand are subject to long periods of deep flooding annually. In the 1972/73 crop year, Kongchantuk (1972) reported that about 0.82 million ha of rice areas were planted to floating rice varieties. Recently, Molle and Keawkulaya (1998) reported changes in rice ecology in the Central Plain of Thailand, attributed to land modifications and infrastructure made to control flood which resulted in the reduction of the deepwater area. The harvested area under the deepwater ecosystem was estimated at about 0.810 million ha (9.77 percent of the wet season rice area) in 1977/78 and 0.160 million ha (1.92 percent of the wet season rice area) in 1997/98. However, the area under the deepwater ecosystem is believed to be higher but most fields are very often left unplanted during the flooding period. Yield contribution from the deepwater ecosystem was small, approximately 1.442 million tonnes in the 1977/78 and 0.312 million tonnes in the 1997/98 crop years (Table 1). Average yield in the deepwater ecosystem was generally low, at about 1.95 t/ha.
Upland: Upland rice constitutes the smallest rice ecology in Thailand. In the 1977/78 crop year, the area under the upland ecology was estimated to be about 0.300 million ha representing approximately 3.62 percent of the wet season rice area (Table 1). A drastic reduction in rice area under the upland ecosystem was observed in the past two decades. In the 1997/98 crop year, upland rice accounted for less than 1 percent of the area and production.
2.3 Production Constraints in Different Ecologies
Rainfed Lowland: Rice production in the rainfed lowland environment, being dependent on rainfed conditions, is very vulnerable to climatic variability. Yield fluctuation is common among rice grown in rainfed environments. Major production constraints are: rainfall variability, drought, submergence, and inherent low soil fertility, especially in the northeastern region (Table 2). Infrastructure at farm level in most rainfed lowland rice areas is very poor and cannot support a high level of rice production.
Table 2. Some Chemical Properties of the Rice Land Soil in Different Regions (Adapted from Srisen et al., 1979)
|
Region |
Chemical Properties |
||||
|
pH |
Organic |
CEC |
Available P |
Extractable K |
|
|
Northeastern |
5.0 |
0.72 |
4.9 |
3 |
47 |
Deepwater: Drought at early vegetative phase, long term deep flooding at late vegetative phase to early ripening phase, and weed competition are the most important production constraints in the deepwater ecosystem. Very abnormal deep flooding in the 1995/96 crop year caused serious yield losses in this ecosystem.
Upland: Drought, poor soil fertility, and weed competition are the most important production constraints in upland ecosystem.
2.4 Yield Potential of Released Varieties and Evidence of Yield Gaps in Different Ecologies
Rainfed Lowland: Released rice varieties for the rainfed lowland ecology are shown in Table 3. Most of the rainfed lowland rice areas are planted to improved traditional and local varieties which vary among locations. These varieties are mostly photoperiod sensitive. Their yield potential is generally lower (about 4.5-6 t/ha) but they have better grain quality and characteristics than HYVs. The most common popular variety currently grown in the rainfed lowland areas is Khao Dawk Mali 105. In the 1997/98 crop year, Khao Dawk Mali 105 occupied approximately 26 percent of the area and contributed 22 percent to wet season rice production (Centre for Agricultural Statistics 1999a).
Table 3. Yield Potential of Released Varieties and Yield Gaps in Different Ecologies
|
Ecologies |
Released Varieties |
Yield Potential (t/ha) |
Yield Gaps |
|
Irrigated |
RD10, RD21, RD23, Suphanburi 60, Suphanburi 90, Suphanburi 1,
Suphanburi 2, Khao Jao Hawm Suphanburi, Khao Jao Hawm Khlong Luang 1, Phisanulok
60-2, and Chainat 1 |
6-8 |
high |
|
Rainfed Lowland |
RD6, RD8, RD15, Khao Dawk Mali 105, Khao Tah Heang 17, Chumpae
60, Niew Ubon 1, PathumThani 60, Pitsanulok 60-1, Leaung Pratew 123, Kaen Jan,
and Phattalung 60 |
4.5-6.0 |
very high |
|
Deepwater |
RD17, RD19, Huntra 60, Prachinburi 1, Plai Ngahm Prachinburi,
Pin Gaew 56, Leb Mue Nahng 111, and Tapow Gaew 161 |
3-4 |
small |
|
Upland |
Sew Mae Jan, Khao Pong Krai, Jao Haw, Nam Roo, R258, Goo Maung
Luang, and Dawk Phayom |
2-3 |
small |
Irrigated: Released rice varieties for the irrigated ecology are shown in Table 3. Most of the dry season irrigated rice areas are planted to several high yielding varieties (HYVs) such as Chainat 1, Suphanburi 60, Suphanburi 90, RD23, RD10, RD15, Suphanburi 1, and Suphanburi 2. But Chainat 1 is the most popular variety currently grown in the irrigated ecosystem. In the 1998 dry season, Chainat 1 accounted for approximately 57 percent of the area and 58 percent of production (Centre for Agricultural Statistics 1999b). Yield potential of these varieties is high at about 6-8 t/ha. Yield gaps in irrigated ecologies are still high, especially in wet season rice cropping, due mainly to limited irrigation water, low inputs used, and crop losses caused by diseases, insects and pests. Narrowing yield gaps in the irrigated ecology is still possible.
Deepwater: Released rice varieties for the deepwater ecosystem are shown in Table 3. Most of the deepwater areas are planted to local and traditional improved varieties such as Pan Tawng, Khao Banna, Plai Ngahm Prachinburi, Huntra 60, Leb Mue Nahng 111, Pin Gaew 56 etc. Yield potential of deepwater rice varieties, both local and traditional, are generally low, giving about 3-4 t/ha. However, newly developed improved plant type deepwater rice lines have higher yield potential of about 4-5 t/ha. The yield gap in the deepwater ecosystem is generally small.
Upland: Released rice varieties for the upland ecosystem are shown in Table 3. The yield potential of these varieties is generally low, often about 2-3 t/ha. Similar to the deepwater ecology, the yield gap in the upland ecosystem is also small.
3. PROGRAMME FOR NARROWING THE YIELD GAPS
3.1 Historical Perspective
Increasing rice production in Thailand in the past was largely attained by expanding the cultivated areas and to some extent, by increasing the yield. Since rice land is limited and expanding the cultivated area to marginal land will result in low yields, increasing the yield therefore, seems to be the most effective means to increased rice production. In Thailand, good grain characteristics and quality are the most important traits needed to be maintained while efforts are made to improve average yield. Therefore, average yield in Thailand is relatively low compared to other countries in this region.
3.2 Activities and Results of Programmes to Narrow Yield Gaps During the Last Two Decades
To narrow yield gaps during the past two decades, several programmes/activities have been implemented.
Rice Varietal Improvement Programme: Development of HYVs is the most effective means of narrowing yield gaps which contributed greatly to increasing rice production. Narrowing the yield gap through the development of HYVs became successful in irrigated environments, especially in dry season rice production. Several HYVs with different disease and insect pest reaction notably RD10, RD21, RD23, Suphanburi 60, Suphanburi 90, Suphanburi 1, Suphanburi 2, Khao Jao Hawm Suphanburi, Khao Jao Hawm Khlong Luang 1, Phisanulok 60-2, and Chainat 1, were developed in the past two decades. Some varieties are still popular and widely grown until the present time. The average yield of these varieties was estimated to be about double that of traditional varieties.
Seed Production and Seed Exchange Programme: The importance of good seed in crop production is generally acknowledged. Farmers usually keep their own seed for next season’s planting. The quality of farmers’ seeds is generally lower than the standard. In order to improve rice yield and grain quality by utilization of standard seed in rice production, a seed production and seed exchange programme was implemented during 1981-1986. Instead of buying rice seed from seed agencies at high cost, farmers can bring their own seed in exchange for good seed at the same price.
Production Technology Improvement Programme: Apart from cultivar development, improvement of production technology is needed in narrowing the yield gaps. In general, transplanting is the most popular planting method for rice production, but is labor intensive for seedling preparation and transplanting, resulting in high cost of production. In order to reduce the cost of rice production and increase yield, wet seeded rice technology or “Nah Wan Namtom” has been developed. The project was implemented in 1981-1986 under the 5th National Economics and Social Development Plan. Wet seeded rice technology is widely adopted by farmers. More than 90 percent of irrigated rice areas are currently using the wet seeded rice method.
Rainfed Rice Improvement Programme: The first phase of the programme was implemented during 1983-1985 under the 5th National Economics and Social Development Plan and extended to the second phase during 1986-1990 under the 6th National Economics and Social Development Plan. The main objective is to improve rice production in rainfed environments, especially in poor smallholder subsistence lowland rice farms, through technology development and technology transfer. Several improved rice varieties/lines such as RD6, RD7, RD8, RD10, RD13, RD15, RD23, BKN6902-3-1, BKN7914-179-4-1 and Niew Ubon 1 were recommended. Apart from cultivar development, production technology for rainfed rice, especially crop establishment by direct dry seeded method was developed for drought prone environments (Rice Research Institute 1987a). About 20 percent of rice areas in the rainfed lowland ecology are currently dry seeded.
Upland Rice Production Improvement Programme: The programme was implemented during 1982-1986 under the 5th National Economics and Social Development Plan. It was the continuation of the original upland rice production improvement programme under The Royal Initiated Project. The objective of the programme was to increase the level of rice self-sufficiency in the upland ecosystem. Several upland rice varieties such as Sew Mae Jan, Khao Pong Krai, Jao Haw, Nam Roo, R258, R293, Blechai, and Motoza, were developed.
Land Consolidation, Dike and Ditch Construction Programme: Apart from component technology development, infrastructure and rehabilitation of paddy fields was also needed in narrowing the yield gap because rice cultivars can fully express their yield potential only when they are planted under a favourable environment. Favourable environments permit an effective use of inputs for yield improvement. Most of the ricelands in Thailand, especially in the rainfed ecosystem, have poor infrastructure. Therefore, rainfed rice is generally grown under poor management with low inputs, resulting in very low yield, usually less than 2 t/ha. The land consolidation, dike and ditch construction project aims to improve the infrastructure of paddy fields and increase rice yields. About 0.275 million ha of rice land have been consolidated and 1.655 million ha had dike and ditch systems constructed, mainly in the central region (Table 4). Yield increase after land consolidation was estimated to be about double the average yield in this ecosystem. The programme will be continued to further expand the area under land consolidation by about 10,000 ha annually.
Table 4. Land Consolidation, Dike and Ditch Construction for Rice Production by Region as at end of 1996. (Centre for Agricultural Statistics 1998)
|
Region |
Land Consolidation (ha) |
Dike and Ditch (ha) |
||
|
Intensive |
Extensive |
Indirect |
Direct |
|
|
Northern |
10,380 |
73,521 |
51,920 |
133,278 |
|
Total |
94,205 |
180,542 |
446,137 |
1,028,939 |
Table 5. Water Resources Development Completed and Pump Irrigation for Rice Cultivation in Thailand as at end of 1996. (Centre for Agricultural Statistics 1998)
|
Region |
Total Irrigated |
Pump Irrigation for Rice |
|
|
Wet Season |
Dry Season |
||
|
Northern |
1,248,841 |
51,938 |
59,642 |
|
Whole Kingdom |
4,713,738 |
173,235 |
129,851 |
3.3 Issues and Challenges in Narrowing the Rice Yield Gap in the Country
Rice production in Thailand in the past three decades has been a balance between yield and quality. Emphasis is currently more on quality than quantity. Consequently, the national average rice yield is still low inspite of the several programmes that had been implemented in narrowing rice yield gaps during the past two decades. Since land and water resources for rice production are limited and the country has to increase its production to meet the increasing demand for domestic consumption and to be more competitive in the world market, the national rice industry needs an effective production system to narrow the yield gaps. Both agricultural technology development and farm infrastructure improvement are, therefore, of utmost importance.
Rainfed Lowland Ecology: To narrow the yield gap in the rainfed lowland ecology, improvement of farm infrastructure such as land leveling, irrigation and drainage facilities, and farm road construction are needed. Improvement of farm infrastructure creates a favourable environment for rice growth and effective utilization of inputs for rice production. Good Agricultural Practices (GAP) for rice production in rainfed environments are being developed.
Irrigated Ecology: Irrigated rice will become the most important rice ecosystem and contribute significantly to national rice production in the future. Good practices for rice production at all growth phases, and post-harvest technology are needed in narrowing the yield gap in the irrigated ecology. Exploration of water resources and improvement of farm infrastructure can significantly increase rice yield.
4. CONCLUSIONS AND RECOMMENDATIONS
Rice is the most important crop in Thailand. The total area under rice is estimated to be about 11 million ha, representing approximately 40 percent of the cropped land area. Rice lands can be classified as irrigated, rainfed lowland, deepwater, and upland ecosystems. The average rice yield in Thailand is relatively low, often less than 2 t/ha. Several attempts have been made to improve rice yield in the past two decades through varietal and agronomic improvement and the development of water resources for rice production. Yield improvement through these efforts was small and needed to be further enhanced.
Rainfed lowlands and irrigated areas are the most important rice production ecosystems in Thailand. In the 1997/98 crop year, rainfed lowlands accounted for 66 percent of the area and 49 percent of production while irrigated rice accounted for 32 percent of the area and 49 percent of production. The area under deepwater and upland ecologies are very minor and contribute very little to national rice production. Yield gaps in rainfed lowlands and irrigated ecologies are high.
Rice production in the rainfed lowland environment being dependent on rainfed conditions, is very susceptible to climatic variability which results in low yields. Major production constraints are related to poor paddy field infrastructure and unfavourable environmental factors such as rainfall variability, drought, submergence, and inherent low soil fertility. To narrow the yield gap in rainfed lowland environments, improvement of farm infrastructure such as land leveling, irrigation and drainage facilities modifications, and farm road construction should be done before the introduction of improved production technologies. Technology components to improve rice yield in the rainfed ecosystem are the adoption of improved varieties, use of healthy and good seed, appropriate field preparation and planting methods, optimum planting date and proper crop management, soil fertility improvement and correct fertilizer application, good water control, integrated crop protection, proper harvesting date, and post-harvest technologies.
In irrigated ecosystems where most environmental factors are favourable for rice growth, development and production, narrowing the rice yield gap in these ecosystems should be done through the application of good agricultural practices for rice production during all growth phases. The development of HYVs will contribute greatly in narrowing the yield gap in irrigated environments. Hybrid rice with acceptable grain quality is also possible. The utilization of good and healthy seed can play an important role in increasing rice yield. Good land preparation with an appropriate planting method such as the wet seeded rice cultivation method will guarantee good crop stand establishment. Water management and correct fertilizer application for proper crop growth and development at all growth stages and high production are also needed in narrowing the yield gap. Adoption of integrated crop protection technologies to control pests and weeds can significantly increase rice yield in irrigated ecosystems. Harvesting the crop at about 30 days after seed-set and reducing grain moisture to about 14 percent can further reduce yield losses and maintain good grain quality, especially in dry season rice cropping.
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