Number of newly developed rice cultivar and major achievements in character improvement, 1960 s-1990 s s 1980 s 1990 s. 1st half.

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1 Achievements and Advanced Technology of Rice Production in Korea Chapter 6 practices of growers. The priority of rice breeding before the 1st of 1970 s was on high yield and developing resistance to lodging, diseases and environmental stresses rather than grain quality. The focus was then changed to developing resistance to disease and insect pests and high grain quality rather than high grain productivity from the 2nd of 1970 s to the 1st of 1980 s. From the 2nd of 1980 s, the improvement of grain quality was the major objective of rice breeding. The rice breeding program was not placed in motion during the 2nd of 1960 s in spite of efforts on improving the resistance to lodging and blast disease, nitrogen responsiveness, and high yield in japonica rice combinations. Although only 12 new japonica rice cultivars, including selected ones from the introduced Japanese rice varieties, were developed during 1960 s, 11 japonica and 25 Tongil-type high-yielding rice cultivars were developed through the active international cooperation with IRRI and the adoption of rapid-generation-advancement breeding system during 1970 s. Hence, self-sufficient rice production was achieved in 1975, and a breakthrough of 5.8 million ton production of milled rice and the highest yield potential per hectare around the world were attained in The first high-quality japonica cultivar resistant to stripe virus disease, Nagdongbyeo (Milyang 15), was developed and widely distributed in the southern lowland area during that time. In addition, the Tongil-type rice cultivars were considerably improved in grain quality and multi-resistance to blast, stripe virus, bacterial blight diseases and brown planthopper in 1970 s (Table 6.2) (Hong et al. 1999). Although the Tongil-type rice cultivars played a major role in achieving self-sufficiency of rice production during 1970 s~1980 s, their growing area rapidly decreased from 1978 after the largest extending to 76% of total rice cultivation area mainly due to their susceptibility to cold and relative inferiority in marketing quality as compared with Table 6.2 Number of newly developed rice cultivar and major achievements in character improvement, 1960 s-1990 s Item 1960 s 1st 2nd 1st 1970 s 1980 s 1990 s 2nd 1st 2nd 1st 2nd Number of newly developed rice cultivars Japonica Tongil- type Total Cultivated area of Tongil-type rices (%) Major achievements Japonica in character improvement BL SV Tongil- type - Semi-dwarf erect leaf, HY, LR, BL, SV, BPH - - 0~23 45~76 27~34 11~22 0~4 - LR, CT, BL, BB, BPH, Short-term BB,CT,BPH, HQ Semi-dwarf erect leaf, HQ, CT, ST, HY, ADS, AFP Super yielding, Aromatic rice BL: Resistance to blast, SV: Resistance to stripe virus, LR: Lodging resistance, CT: Cold tolerance, BB: Resistance to bacterial blight, BPH: Resistance to brown planthopper, HQ : High quality, ST: Salt tolerance, HY: High yielding, ADS: Adaptability to direct seeding, AFP: Adaptability to food processing (special rice) 61

2 Rice Culture in Asia japonica rices. Fifteen Tongil-type rices and 39 high-quality and high-yielding japonica rice cultivars were developed during 1980 s through the activated japonica rice breeding to incorporate semi-dwarf, desirable canopy architecture and resistance to lodging, cold, and major diseases. The recommendation of new Tongil-type, high-yielding rice cultivar stopped in 1987, but the research works on higher grain production continued in the form of super yielding rice project for food processing. During this time, the first high-quality japonica rice using anther culture technique, Hwaseongbyeo, was developed. Furthermore, the first resistant japonica variety to brown planthopper, Hwacheongbyeo, was developed through this haploid breeding system. Table 6.3 Item Newly developed japonica rice cultivars for special utility and cultivation in 1990 s Newly developed rice varieties Special rices adaptable to food processing Short-term rice cultivars adaptable to late planting Rice cultivars adaptable to direct seeding Jinbuchalbyeo, Hwaseonchalbyeo, Sangjuchalbyeo, Dongjinchalbyeo (glutinous), Daeribbyeo 1 (large grain), Yangjobyeo (chalky endosperm), Hyangnambyeo, Mihyangbyeo (aromatic rice), Aranghyangchalbyeo, Seolhyangchalbyeo (aromatic glutinous rice), Heugjinjubyeo, Heugnambyeo (blackish purple rice) Shinkeumobyeo, Keumobyeo 1, Keumobyeo 2, Geurubyeo, Mananbyeo Nonganbyeo, Juanbyeo, Ansanbyeo, Donganbyeo, Daesanbyeo, Gwanganbyeo, Hoanbyeo, Nonghobyeo, Junganbyeo Figure 6.5 The first Tongil-type rice cultivar Tongil developed from a threeway cross among two semi-dwarf indica and japonica rice varieties In 1990 s, 70 high-quality japonica rice cultivars, including 12 special rices such as glutinous, large grain, chalky endosperm, aromatic, and colored rices were developed. There were also some short-term rice cultivars adaptable to late transplanting after cash crops and nine cultivars adaptable to direct seeding (Table 6.3). Six Tongil-type rices were developed as high-yielding aromatic rices and super-yielding rice cultivars during the 2nd of 1990 s. The japonica rice cultivars developed in 1990s were improved, especially in canopy architecture and grain appearance, as well as eating quality of cooked rice. They have better yield potential with enhanced safety in rice cultivation. In addition, several special rice cultivars were developed for diversification of processing utility and for special cultivation such as direct seeding or late planting after cash crops. 62

3 Achievements and Advanced Technology of Rice Production in Korea Chapter Progress in rice breeding system and techniques The conventional breeding systems such as pedigree and bulk method mainly used in handling the japonica rice materials were modified into general breeding systems accompanying the rapid generation advancement (RGA) scheme utilizing the greenhouse (Figure 6.6) or IRRI field during winter season. Thus, changes were made to the real rice breeding works to introduce useful characteristics from tropical indica rice from the 2nd of 1960 s. Several rice breeding mutations through irradiation were attempted during this time, but were terminated with almost no practical outcomes. The RGA rice breeding system and rapid extension of Tongil-type rice cultivars through seed multiplication in IRRI field during winter were actively carried out during 1970 s since the development of the first Tongil-type rice cultivar Tongil in 1971.(Figure 6.5) Also, the breeding efficiency was largely enhanced through the continuous improvement in testing techniques for evaluating the grain quality and resistance to disease and insect pests during this time. Figure 6.6 Figure 6.7 Greenhouse with RGA rice breeding system Rice breeding through anther culture technique (callus induction, differentiation of green plant, diploid & haploid rice plants) The haploid rice breeding utilizing the anther culture technique (Figure 6.7) was established for japonica rice since the first varietal development of Hwaseongbyeo using this system in The rice breeding period was shortened to 5~6 years by this technique. A total of 15 rice cultivars were developed through anther-culture breeding system during 1980 s~1990 s (Figure 6.8). Although the hybrid rice breeding using the cytoplasmic genic male sterility (CGMS) was initiated in the early 1970 s, the real breeding work was actively conducted during 1980 s, and the first development of hybrid rice Suweonjapjong No.1 and No.2 was realized with a milled rice yield of 7.3~8.3 t/ha in However, they were not distributed to the farmers due to difficulties in hybrid seed production and poor acceptance. In addition, a recurrent population improvement breeding scheme using genetic male sterility (GMS) was operated to enhance the opportunity of desirable recombination by breaking undesirable characteristic linkages and accumulate useful genetic factors related to diseases and insect pests by supporting the existing conventional pedigree breeding system. 63

4 Rice Culture in Asia Breeding system Conventional pedigree method Rapid generation advancement Anther culture technique Figure 6.8 Figure Hybridization (H) Generation advancement (years) Pedigree nursery (P) Yield trial (YT) H P YT LA T HAC* YT LAT PFT Local adaptability test (LAT) * Hybridization & anther culture Reduction of breeding period by rapid generation advancement and anther culture technique. Cold tolerance test nursery with cold-water flowing system in Chuncheon PF T Pilot farming test (PFT) The establishment of testing system and effective selection of breeding lines for cold tolerance was carried out with the construction of cold-tolerance test nursery. Rice varieties were subjected to a cold-water irrigation (17 ) drained from Soyang dam in Chuncheon since 1979 (Figure 6.9). This facility has been utilized by IRRI as the international rice cold-tolerance test nursery since For the effective in situ selection and shuttle breeding for salinity and cold tolerance, Namyang and Gyehwa Substations were established in westerncoastal reclaimed area, while Jinbu, Unbong, Sangju, and Yeongdeok Substations were constructed in high altitude areas of north eastern and southern, midmountainous, and eastern-coastal cold areas, respectively, from 1978 to The establishment of embryo rescue technique was realized to obtain an interspecific hybrid between different genomic wild species and cultivars and to introduce resistant genes against diseases and insect pests from wild rice species to cultivars via recurrent backcrossing during 1990 s. Furthermore, the basic techniques to Table 6.4 Improvement in rice breeding technology and system Period Major progress in rice breeding technology & system Before 1970 Settlement of conventional breeding system of pedigree and bulk methods Mutation breeding by irradiation 1970 s Development of Tongil cultivar from a three-way remote cross between semidwarf indica and japonica rices Introduction of rapid generation advancement (RGA) scheme in conventional rice breeding system Establishment of effective testing & evaluation technologies for resistance to pests and grain quality 1980 s Practical settlement of anther culture technique in japonica rice breeding Development of Tongil-type hybrid rices using cytoplasmic- genic male sterility (CGMS) Improvement of cold & salinity tolerance testing system Development and operation of recurrent population improvement breeding scheme using genetic male sterility (GMS) 1990 s Establishment of embryo rescue technique for interspecific hybridization between wild rice species and cultivars Development of basic technique for molecular breeding Driving of effective rice breeding system for direct seeding Mutation breeding for high grain quality and diversification of food-processing utility 64

5 Achievements and Advanced Technology of Rice Production in Korea Chapter 6 ensure the practical utilization of biotechnologies in rice breeding were developed, and studies on the improvement of evaluation techniques and breeding systems were actively pursued for improving the adaptability to direct seeding and high-quality or diversification of food-processing utility in recent years (Table 6.3 & 6.4) (NCES 1990) Achievements in the improvement of major agronomic characteristics Milled rice yield of newly developed cultivars during 1990 s increased by about 43% in high-quality japonica rices and about 41% in Tongil-type rices as compared with those of japonica rices during the first of 1960 s and those of Tongil type rices during the first of 1970 s, respectively (Table 6.5 & Figure 6.10) (Choi 1999). In particular, the japonica rice cultivars were largely improved in lodging tolerance through the introduction of semi-dwarf gene, stiff culm, and erect plant type since The maturity of rice cultivars was also diversified from extremely early to medium-late maturing since 1970 s (Figure 6.11), which largely contributed to the increasing of the grain yield in alpine and mid-mountainous areas, as well as, in lowland areas. Table 6.5 Changes in milled rice yield of developed cultivars during the last four decades Ecotype Item 1st 1960 s 2nd 1st 1970 s 1980 s 1990 s Japonica Average (t/ha) (Index) (100) (103) (124) (115) (130) (133) (133) (143) Range (t/ha) ~3.85 ~4.01 ~4.74 ~5.28 ~5.34 ~5.31 ~5.96 Tongil- Average (t/ha) Type (Index) - - (100) (104) (114) (124) (141) Range (t/ha) ~5.54 ~5.81 ~6.05 ~6.77 ~7.41 2nd 1st 2nd 1st 2nd The first japonica rice cultivar resistant to stripe virus disease, Nagdongbyeo was developed in 1975 and since then, several other japonica rice cultivars resistant to the stripe virus disease were continuously developed. In addition, high-quality japonica rice cultivars were extensively improved for resistance to major diseases and insect pests since The first resistant cultivar to brown planthopper Hwacheongbyeo was developed through the anther culture haploid breeding during this time. Milled rice yield (t/ha) Figure 6.10 Tongil-type Japonica Year Changes in milled rice yield (t/ha) of newly developed rice cultivars during the last four decades 65

6 Rice Culture in Asia Heading date Sep. 01 Aug. 25 Aug. 20 Aug. 15 Aug. 10 Aug. 05 Jul. 30 Jul. 25 Figure 6.11 Tongil-type Japonica Year The Tongil-type rice cultivars were also rapidly improved for multi-resistance to major diseases and insect pests, and soon after a severe occurrence of neck blast in 1978, new blast-resistant varieties were developed (Table 6.6). Japonica rice cultivars were considerably improved in terms of lodging and cold tolerance, and the Tongil-type rice cultivars were relatively improved in terms of cold tolerance, adaptability to late planting, and grain shattering (Table 6.7). Varietal variation of newly developed rice cultivars in maturity since Although the development of shortterm early rice cultivars started from the late 1970 s, the first short-term rice cultivar, Keumobyeo, suitable for ext-remely late transplanting after cash crop cultures, was developed in Subsequently several short-term rices such as Keumobyeo 1, Keumobyeo 2, Geurubyeo, and Mananbyeo were continuously developed during 1990 s. Table 6.6 Improvement of resistance to major diseases and insect pests in newly- developed japonica and Tongil-type rice cultivars Ecotype Cultivar Bred year Blast Bacterial blight Virus Brown Planthopper Leaf Neck K1 K2 K3 SV DV BSDV Japonica Jinheung 1962 MS MS S S S S S S S Nagdongbyeo 1975 S MS S S S MR S S S Seomjinbyeo 1982 M MR R S S MR S S S Palgongbyeo 1986 M MR S S MS R M M S Hwacheongbyeo 1986 MR MR R S S MR S S MR Hwayeongbyeo 1991 M MR R R R R S S S Tongil- Tongil 1971 M MS R MR S R S S S Type Milyang M MS S S S R MR S S Milyang MR M R MR S R MR MS R Taebaegbyeo 1979 R R MR MR MR R MR M S Samgangbyeo 1982 MR R R MR MR R MR M R Namyeongbyeo 1986 MR R R R R R MR MR S Andabyeo 1998 R R R R S R R MR R R: resistant, MR: moderately resistant, M: medium, MS: moderately susceptible, S :susceptible, SV: stripe virus, DV: dwarf virus, BSDV: black- streaked dwarf virus. 66

7 Achievements and Advanced Technology of Rice Production in Korea Chapter 6 Table 6.7 Improvement of tolerance to various environmental stresses in newlydeveloped japonica and Tongil-type rice cultivars Ecotype Cultivar Bred year GA- LT Seedling stage Cold tolerance Heading Spikelet delay sterility Adaptability in late planting AHR GYLP LT ST GS Japonica Jinheung 1962 R R R M IS H MS M Ha Nagdongbyeo 1975 R R MR MS IS M MS M Samnambyeo 1981 R R MR R IS H R M Odaebyeo 1982 R R MR MR SE L M S Anjungbyeo 1991 R R R R IS M R M Tongil- Tongil 1971 M S S S IS L R S E Type Milyang M S MS S IS L R S Pungsanbyeo 1980 MR MS M M IS M R S ME Samgangbyeo 1982 M S MR M IS M MR S GALT: Germination ability at low temperature, AHR: Abnormal-heading responsiveness, GYLP: Grain yield in late planting, R: resistant, MR: moderately resistant, M: intermediate, MS: moderately susceptible, S: susceptible, IS: insensitive, SE: sensitive, H: high, M: medium, L: low, LT: lodging tolerance, ST: salinity tolerance, GS: grain shattering, Ha: hard, E: easy, ME: medium easy The grain quality of Tongil-type rice cultivars was rapidly improved in terms of eating quality of cooked rice by reducing the amylose content of endosperm and was steadily improved in terms of marketing quality through the selection toward clear and short grain during 1970 s-1980 s. Through the concentration of steady efforts to grain quality improvement of Tongil-type rices, short, clear, and low-amylose rice cultivars, Jungwonbyeo and Chilseongbyeo, were developed in The grain quality of japonica rice cultivars has been improving in both grain appearance and palatability of cooked rice since 1980 (Table 6.8) (Choi 1998). The recent breeding efforts on diversification of food-processing utility had realized the development of special rice cultivars such as large kernel, chalky endosperm, aromatic, and colored rices (Table 6.9) Prospect of rice varietal improvement The world rice production in 2010 is projected to be about 445 million tons harvested from 154 million hectares of cultivation acreages, and the ratio of stock rice is expected at about 12~13% of consumption amount. The domestic rice production in 2004 is also expected to maintain self-sufficiency and about 17% of stock rice ratio (Kim & Park 2000, Kim & Kim 2000). In Korea unstable environmental conditions in rice production may continue due to the greenhouse effect and unexpected local meteorological disasters. In addition, deterioration 67

8 Rice Culture in Asia Table 6.8 Ecotype Cultivar Improvement of grain quality in Tongil-type and japonica rice cultivars since 1970 Bred year Brown rice (mm) Length Width Thickness L/W ratio Chalkiness (WC/WB) (0-9) Japonica Pungok /1 L FG Jinheung / FG Dongjinbyeo / G Ilpumbyeo / E Average Tongil- Tongil /5 ML A type Milyang / FG Samgangbyeo / FG Jungwonbyeo / G Average GT: gelatinization temperature, WC/WB: white core/white belly, A: acceptable, FG: fairly good, G: good, E: excellent GT Amylose (%) Protein (%) Palatability of cooked rice Table 6.9 Development of special rice cultivars suitable for food-processing Cultivar Bred year Heading date Culm length (cm) Milled rice yield (t/ha) 1,000- kernel weight (g) L/W ratio Chalkiness (WC/WB) (0-9) Color of seed coat Aroma (0-9) Amylose (%) Daeribbyeo 1 93 Aug /0 YW Hyangmibyeo 1 93 Aug / Hyangnambyeo 95 Aug / Hangmibyeo 2 96 Aug / Yangjobyeo 94 Aug / Aranghyang 97 Aug chalbyeo Heugjinjubyeo 97 July BP Heugnambyeo 97 Aug Seolhyang 99 Aug YW chalbyeo L/W ratio: length/width ratio of brown rice, YW: yellowish white, BP: blackish purple of paddy soil may be more severe with the increased air and water pollutions, and the shortage of irrigation water will become more serious in the future. Greenhouse effect will also result in an increase in the occurrence of diseases. The pressure on the opening of rice market from some export countries will be stronger, and the socioeconomic situation will also be unfavorable for maintaining self-sufficiency in domestic rice supply and demand. 68

9 Achievements and Advanced Technology of Rice Production in Korea Chapter 6 Accordingly, the rice breeders must come to terms with the outlook of our rice industry and be ready for the expected changes in environmental and socioeconomic situations. Recently, an effective selection and introduction of useful agronomic target genes were made possible through the utilization of DNA markers associated with target genes and biotechnological method of gene transformation after the biochemical pathway and mechanism of the characteristic expression and relevant genetic factors were elucidated. In addition, the possibility of desirable recombination and enhancement of useful expression will be gradually realized through the identification of target gene locus, gene cloning, and transformation. The genetic variation of rice breeding materials will be diversified through the introduction of various useful alien genes using biotechnological procedures in the future, which may be helpful for increasing the stability of self-sufficient rice production and enhancing the competitiveness of our rice products in the world trade market. The yield potential in milled rice is expected to be increased to 6.5 t/ha in high-quality japonica rice and 10.0 t/ha in super-yielding rice cultivar by The grain quality will be improved continuously toward high marketing quality of milled rice and excellent palatability of cooked rice. Wider diversification of morphological and physicochemical characteristics of rice grain for various food-processing utilities and hygienic functions through chemical mutation and biotechnological genetic control will also be performed. Specifically, breeding efforts on the enhancement of hygienic functions in rice will lead to the development of diversified special rices, such as a low allergen rice for atopic dermatitis patients, low protein rice for nephrism patients, high lysine or high sulfur-containing amino-acids rice, high procarotenoid rice, high fiber rice, giant embryo rice, among others (Choi 1998). Complex resistance to major pests and environmental stresses suitable for each relevant region will be gradually strengthened using introduced rice germplasm from wild species and through the countermoving breeding against global climatic changes in the agricultural environment. To increase the utilization of paddy field, diversification of short-term rice varieties adaptable to various cropping system will be developed continuously not only to take advantage of the wide adaptability with less variation of grain yield but to be more adaptable to extremely late planting through the appropriate combination of basic vegetative phase and relative photo- and thermo-insensitiveness in flowering response. The varietal improvement of direct seeded rice for low-cost and labor-saving cultivation will continue via mass selection under dry or water seeding conditions, and screening of germination ability and shoot emergence under soil at low temperature, lodging tolerance, and adaptability to dense planting. 6.3 Mechanization of rice production Rapid economic growth has influenced the structure of agriculture in Korea. The farming population which was 37.5, 21.1, and 9.7% in 1975, 1985, and 1997, respectively and is expected to decrease continuously. 69

10 Rice Culture in Asia Proportion of cultivation area (%) Yield in polished rice has increased from 3.8 t/ha in 1975 to 4.5 t/ha in 1985 and 5.22 t/ha in Total rice production in 1997 was about 5.8 million tons, maintaining selfsufficiency. However, increasing farm wages and decreasing availability of farm labor have resulted in much higher costs of production. One of the most significant changes in rice production in recent years is the technology development of direct seeding method. Until early 1980 s, the ultimate target of rice crop was the quantitative relation and the primary concern was maximum harvest with maximum input. However, much emphasis has been recently placed on finding ways to reduce the production inputs and achieve greater profitability. Thus, technologies of direct seeding and machine transplanting of infant seedlings are the prime concerns. Since 1985, direct seeding and machine transplanting infant seedling with have actively been studied as remarkable labor-saving technologies based on the research conducted by the National Crop Experiment Station (NCES), National Honam Agricultural Experiment Station (NHAES), National Yeongnam Agricultural Experiment Station (NYAES), nine Province Agricultural Research and Technology Centers (ADTEC), and leading farmers Brief introduction of changes in rice cultivation technologies Up to the late 1970 s, most parts of the paddy fields in Korea had been cultivated by hand transplanting. Rapid industrial growth has led to the outflow of labor force from rural to urban areas, and farmers were faced with the need of labor-saving. Thus, a machine transplanter was introduced to solve this situation. From 1978, a machine transplanting method using semi-adult seedling with 35 days nursery period was introduced. In 1990, another machine transplanting using infant seedling with only 8 to 10 days old was developed as a labor-saving technology. Subesquently, techniques for machine transplanting cultivation were developed and are completely established at present. Thus, in 1999, the machine transplanted paddy occupied 92.5% of the total paddy area of 1,059,000 hectares (Figure 6.12). From 1991, various direct seeding cultivation methods for labor-saving were gradually established through the develo-pment of a new machine, herbicide and cultivation technique, and the cultivation area of direct seeding 100 showed an increasing trend. By 1995, the area of direct seeding cultivation has been increased up to 80 Hand transplanting Machine transplanting 117,500 hectares, 11.1% of the total 60 paddy fields of Korea, among which direct seeding on dry paddy was 6.4%, Direct seeding and direct seeding on flooded paddy was 4.7%. The area of direct seeding is expected to increase through improvements and counter plans for the prob- Figure 6.12 Year Changes in rice cultivation technologies lems of cultivation technique in the future. 70

11 Achievements and Advanced Technology of Rice Production in Korea Chapter Infant-seedling machine transplanting The development of a raising method for infant rice seedling (8 to 10 days old) is an important technology for labor-saving and cost-reduction in rice production due to very short nursery period compared with semi-adult seedling (35 days old), which is the conventional seedling raising method for machine transplanting in Korea. The raising method of infant rice seedling is very similar with that of the semi-adult seedling except for the seeding rate and nursery period. In 1997, the machine transplanted area wiht semi-adult seedling occupied 67.1% and that with infant seedling occupied 21.2% of the total paddy area. Comparative characteristics between infant and semi-adult seedlings are presented in Table Table 6.10 Comparison between infant and semi-adult rice seedling Items Infant seedling Semi-adult seedling Nursery period (days) 8~10 30~35 Seeding rate (g/tray) 200~ ~130 Leaf number at transplanting 2.5~ ~4.0 Seedling height (cm) 5~8 15~18 Amount of remained endosperm (%) 30~50 0 Seed trays needed (no./ha) * Size of seedling tray: 30 x 60 x 3cm The advantages of infant rice seedling are summarized as follows: Labor-saving: very short nursery period (8~10 days) and easier management. Cost-reduction: less number of seed trays (150 trays/ha) required compared with semi-adult seedling (300 trays/ha). Fast seedling growth and rooting after transplanting due to the remaining nutrients (30~50%) in the endosperm of seed. Reduction of environmental damage: less damping-off and physiological seedling rot during nursery period, and low cold injury after transplanting. However, the following cares should be taken on the cultivation of infant rice seedling. Uniform leveling and hardening of paddy soil to prevent damages to seedlings caused by submerging or lodging. Use of less phytotoxic herbicides. Rice seedlings normally grow in the seedbed and require the preparation of seedbed. To remove seedbed easily and prepare for mass production of infant seedlings, a factorystyle multi-layer culture of infant seedling was developed by the National Crop Experiment Station. This automatic raising seedling facilities composed of all raising seedling processes from seeding to the last step of raising seedling. This new method of raising seedling on the shelves has ten tiers at 30 cm interval and can grow 8 to 10 days infant seedlings. 71

12 Rice Culture in Asia Direct seeding cultivation technologies Essentially, there are two methods of direct seeding in rice, dry and wet seeding, based on the physical condition of the seedbed and seeds. In Korea, wet seeding is further divided into two methods: wet drill seeding and water seeding. Recently, a corrugatedfurrow drill seeding was developed. In 1997, the total direct seeded area was 110,600 hectares, which is 10.5% of the total rice paddy, 1,052,000 hectares (Table 6.11). Table 6.11 Major direct seeding (DS) methods and the area of direct seeded rice in Korea, 1997 Direct seeding method % of DS paddy to the total area Area of direct seeded paddy (x1,000 ha) Dry seeded rice (51.7%) Wet seeded rice (48.3%) - Wet drill seeding (22.0%) - Water seeding (26.3%) Total (100%) * Total area of rice paddy in Korea, 1997 was 1,052,000 ha Yield stability in direct seeded rice is relatively low compared with the transplanted rice due to several major problems. A general chart of technology development for the production stability of direct seeded rice in Korea is shown in Figure Production Stability of Rice Cultivar development Low temp. germinability Low-tillering, large panicle plant type Early maturity Lodging resistance Establishment of cultural practices Seeding methods Seeding time Fertilizer application Water management Research on cultivation environment Soil management Integrated pest management Water pollution Ecosystem change Seedling stand stability Lodging prevention Weed control Improvement of seeding method Seeding rate Water management Plant growth regulator Seeder improvement Water management Balanced fertilization Lodging reduction chemicals Ecological control Biological control Promising herbicide selection Physiology and ecology research Figure 6.13 Technology development for production stability of direct seeded rice in Korea 72

13 Achievements and Advanced Technology of Rice Production in Korea Chapter 6 Technology development for increasing the production stability in direct seeded rice requires the establishment of proper cultivation technology, cultivar development adaptable to direct seeding environments, improvement of major problems such as unstable seedling stand, easy lodging, difficult weed control, among others, and also fundamental research for direct seeding cultivation, including soil management and integrated pest management. Dry seeding In dry seeded rice, there are two different seeding methods, flat drill seeding and highridged drill seeding. Generally, conventional method of flat drill seeding having six rows uses dry seeds and soil cover after seeding, with irrigation at 3rd leaf stage. Flat drill seeding has higher working efficiency compared with high-ridged drill seeding for seeding and harvesting operations. However, this seeding method is unstable under severe climatic conditions such as heavy rain or severe drought. For high-ridged dry drill seeding, a drill seeder makes small canals of 25 cm wide and 12 cm depth in the center with every 1.5 meter interval. This canal can be used as irrigation or drainage canal depending on the soil moisture condition. The standard cultural technology of dry seeded rice is shown in Table Table 6.12 Items Standard cultural technology of dry seeding Cultural practices Tillage Land leveling Seeding method Seeding time Seeding rate Seeds Opt. seedling stand Fertilizer Water management Weed control - Once or twice rotavation before seeding - Laser leveling system - Row seeding by a tractor - attachable drill seeder at the final rotavation operation - April 20-May 10-40~60 kg/ha - Dry seeds - 90~150 seedlings/ m2 - N - P 2 O 5 - K 2 O = kg/ha Nitrogen split: Basal-5th leaf stage - Panicle initiation = % - Permanent flooding at 3rd~4th leaf stage of rice - Two systematic herbicide applications are recommended during dry and flooded periods. - Dry period: Propanil mixture herbicides at 12~15 DAS - Flooded period: One-shot granular type herbicides at 3~5 days after flooding Land leveling in direct seeding cultivation is one of the most important cultural practices for improving seedling establishment, and water, nutrient, and weed managements. A laser leveling system was introduced to arrange uniform land leveling for both dry and wet seeding cultivations. With the introduction of laser scraper, a precise leveling was available with only 3.0 cm difference between the high and low portions in the field, while a conventional rotavator revealed about 8.0 cm of level difference (Table 6.13). 73

14 Rice Culture in Asia Table 6.13 Effect of land leveling by laser scraper based on the difference of land level between high and low portions of paddy Difference of land level (cm) Treatment Dry seeding Wet seeding Before After Before After Laser scraper 10.4 < <3.0 Conventional rotavator * Both the widths of laser scraper and conventional rotavator are 3.2m Wet drill seeding Wet drill seeding is commonly practiced for flooded and puddled lands for timely crop establishment (Figure 6.15). Sprouted seeds are sown on or below the puddled soil surface. A wet drill seeding was developed to improve the problems of water seeding such as unstable seedling stand and lodging. A riding-type wet drill seeder with six furrow openers presses the hardened paddy soil to make furrows, which are 5 cm in width and 4 cm in depth. Figure 6.14 Figure 6.15 Leveling by a laser leveling system Wet drill seeding by a transplanter-attachable drill seeder seeding is done mostly by motorized sprayers. The standard cultural practice of wet drilling seeding is shown in Table For the management of diseases and insect, super-wide sprayer was introduced. The maximum distance of chemical spray is about 80 meter (Figure 6.16). Therefore, the total labor hours for chemical spray could be reduced to 10% of that by a conventional power sprayer (Table 6.15). Water seeding Water seeding is a technique in which pre-germinated seeds (2~3 days soaking and 24 h incubation) are sown in standing water. Seeds must be heavy enough to sink in standing water to make anchorage at the soil surface. Water Seedling establishment is very poor. Plant anchorage is weak, leading to lodging at maturity. Higher seedling stand and lodging tolerance combined with stiff culm and deep rooting habit are required. 74

15 Achievements and Advanced Technology of Rice Production in Korea Chapter 6 Table 6.14 Items Standard cultural technology of wet drill seeding Cultural practices Tillage Land leveling Soil hardening Seeding method Seeding time Seeds Seeding rate Opt. Seedling stand Fertilizer Water management Weed control - Rotavate once or twice under flooded paddy - Laser leveling in dry or wet paddy condition - Hardening under flooded condition for 3~5 days after harrowing - Drill seeding by a riding type wet drill seeder (6 rows) - May 1 - June 5 - Pregerminated (1~2 mm) seeds - 30~50 kg/ha - 80~120 seedling/ m2 - N - P 2 O 5 - K 2 O = kg/ha Nitrogen split: Basal - 5th leaf stage - Panicle initiation = % - Draining 1 day before seeding - No irrigation for the first 8~10 days after seeding and thereafter maintain flooded condition - Midsummer drainage at 30, 45, and 60 DAS - One-shot herbicides of sulfonylurea mixture at 8~10 days after seeding (after root anchored) Table 6.15 Effect of superwide sprayer for controlling pest on labor-saving Sprayer Labor required to operate a sprayer (person/ha) Total labor hours (minute/ha) Superwide sprayer 2 26 (10%) Conventional power sprayer* (100%) *Conventional power sprayer attached to a tractor Because water seeding is the most effective labor-saving technology, the area of water seeding will increase with the development of varieties with good seedling establishment and lodging tolerance. Seosan tideland reclamation area, about 10,000 hectares in the western coast of Korea was developed as paddy fields. From 1986, the cultural practice of direct seeded rice including application of agro-chemicals was performed using an aircraft as in California, USA. The standard cultural method of water seeding is given in Table Figure Pest control by a super wide sprayer 75

16 Rice Culture in Asia Table 6.16 Items Standard cultural technology of water seeding Cultural practices Tillage Land leveling Soil hardening Seeding method Seeding time Seeds Seeding rate Opt. seedling stand Fertilizer Water management Weed control - Once or twice rotavation under flooded paddy - Laser leveling in dry or wet paddy condition - Hardening under flooded condition for 1-3 days after harrowing - Broadcast seeding by a motorized seed sprayer or an aircraft - May 1 - June 5 - Pregerminated (1~2 mm) seeds - 30~40 kg/ha - 80~120 seedlings/ m2 - N - P 2 O 5 - K 2 O = kg/ha Nitrogen split: Basal - 5th leaf stage - Panicle initiation = % - Flooded or drained at seeding time - Midsummer drainage at 30, 45, and 60 DAS - One-shot herbicides of sulfonylurea mixture at 8~10 days after seeding (after root anchored) Corrugated-furrow seeding A corrugated-furrow seeding technology is considered as a combination of dry and wet direct seeding methods. Both methods are similar in a sense that corrugated furrow is prepared under dry field condition during final land leveling operation with corrugated rice seeder attached to the back of the rotavator at the same time with basal fertilizer incorporation. However, for the dry seeding method, seeding operation is done simultaneously with corrugated-furrow preparation. In water seeding method, corrugated furrows are initially prepared and then water is irrigated into the field. Subsequently, rice seeds are broadcasted under flooded condition using a motorized seed sprayer. The standard cultural method of corrugated-furrow seeding is shown in Table Effective weed control in direct seeding One of the major problems in direct seeding is the difficulty of weed control due to of severe weed occurrence. A key technology for the success of direct seeding method is the effective weed control technology. Weed growth is strongly affected by cultivation method. Weeds in direct seeding increased 2 to 3 times as compared with transplanting. When the seedlings were not subjected an effective weed control, rice yield loss was about 40~60% in water seeded rice, and about 70~100% in dry seeded rice as compared with 10~35% loss in transplanting cultivation. In Korea, weed control is mainly dependent on herbicide application. For dry seeded rice, two systematic herbicide applications are recommended; one during dry period either before or after rice emergence, and the other during flooding period (within one week after flooding). During dry period, however, there are five alternatives 76

17 Achievements and Advanced Technology of Rice Production in Korea Chapter 6 Table 6.17 Items Summary of corrugated - furrow seeding method Cultural practices Tillage Making corrugated furrow Seeding method Seeding time Seeds Seeding rate Water management Fertilizer Weed control - Rotavate once or twice before seeding - Tractor-attachable corrugated- furrow seeder - Water seeding: seeding by a motorized seed sprayer just after irrigation - Dry seeding: seeding making a furrow at the final rotavation operation - May Pregerminated (1~2 mm) or soaked seed - 40~50 kg/ha - Dry seeding: irrigation just after seeding and drainage (flooding after seedling emergence) - Water seeding: Drainage about five days after seeding for better seedling emergence in case of excessive seed burial - Water flooding up to 6th leaf stage of rice seedling and then follows the conventional water management - N - P2O5 - K2O = kg/ha Nitrogen split: basal at seedling emergence - 6th leaf stage-panicle initiation = % - Herbicides application: pyrazosul./moli., cyhalo./azimsul./moli. at 1.5~2.0 leaf stage of rice to applying herbicide. Herbicidal efficacy was the greatest at the application of 12~15 DAS (just after rice emergence). Recommended herbicides are given in Table Table 6.18 Recommended herbicides and their application systems in dry-seeded rice Period Application time Herbicides Dry 12~15 DAS (after rice emergence). Propanil + Butachlor Thiobencarb Pendimethalin Molinate Flooded * DAS: Days After Seeding 3~5 days after flooding Pyrazosulfuron-ethyl/Molinate Bensulfuron-methyl/Dimepiperate Butachlor Thilbencarb For wet-seeded rice, the success of effective weed control practice mostly depends on good tillage operation, particularly on harrowing operation and the degree of root anchor when first herbicide is applied. One-shot herbicides of sulfonylurea mixture are currently recommended at 8~10 DAS (Table 6.19). 77

18 Rice Culture in Asia Table 6.19 Recommended herbicides and their application time in wet- seeded rice Application time 8~10 DAS (Rice root anchored) 15~20 DAS (Echinochloa: 3rd~4th leaf stage) 30~40 DAS (Echinochloa: 3rd~4th leat stage) * DAS: Days after seeding Herbicides - Pyrazosulfuron-ethyl/Molinate - Bensulfuron-methyl/Dimepiterate - Azimsulsuron/Molinate - Cyhalofop-Molinate/Azimsulfuron - Imazosulfuron/Mefenacet/Dymron - Stem F-34 - Bentazon, 2.4-D Labor-saving effect of direct seeding The competitiveness in rice production should be increased through the introduction of labor-saving technology as in direct seeding, and by turning to large-scale farming. Considering that raising seedling and transplanting are not needed in direct seeding, it is expected to reduce labor demand as compared with transplanting. The labor hour of direct seeding is 246 h/ha for dry seeding and 255 h/ha for wet seeding. This is about 30% lower than 357 h/ha of machine transplanting with aged seedling which is the conventional machine transplanting method. Direct production cost of rice excluding land service charge etc. was reduced by 21% in dry seeding and 16% in wet seeding, as compared with that of machine transplanting with semi-adult seedling (Table 6.20). Table 6.20 Items * US$ 1 = 951 Won (1997) Labor hours and rice production cost of machine transplanting and direct seeding Machine transplanting Semi-adult seedling Infant seedling Dry seeding Direct seeding Wet seeding Labor (h/ha) - Tillage-transplanting 166 (100%) 125 (75) 37 (22) 56 (34) - Field management 191 (100) 196 (103) 209 (109) 199 (104) - Total 357 (100) 321 (90) 246 (69) 255 (71) Direct production cost 1,997 (100) 1,883 (95) 1,570 (79) 1,676 (84) (US$/ha) Research strategies and prospect of direct seeding A long period of time is required to establish the technical system of direct seeding cultivation due to its various cultivation types. Future research strategies on direct seeding in Korea should be based on the followings: Improvement of specific rice varieties for different direct seeding methods 78

19 Achievements and Advanced Technology of Rice Production in Korea Chapter 6 Land leveling using laser-assisted tractor under wet and flooded soil conditions Establishment of effective weed control system and development of new herbicide with broad spectrum Technical development for cultural practices such as seedling establishment, lodging reduction, fertilizer, and water management. Development of appropriate mechanical technology, labor-saving and cost-reduction technologies Establishment of yield stability The Rural Development Administration (RDA) of Korea has established several types of direct seeding methods such as dry drilling seeding, wet drilling seeding, water seeding, and corrugated-furrow seeding. RDA has already initiated the development of direct seeding methods via minimum or zero tillage cultivation. Even though these direct seeding methods are not yet well established, the direct seeding acreage has been rapidly increasing since 1992, and was the largest in 1995 at 117,500 hectares but decreased to about 73,700 hectares in Potential paddy field area of direct seeding in Korea is about 70% of the total rice field area. The government further expects that the direct seeding area will increase by 40 to 50% in the near future. Grain yield in milled rice was 4.45 t/ha in 1995, and this is expected to further increase by 5.15 t/ha in 2004, through improvement of rice varieties and cultivation technology for direct seeding. Labor hours via direct seeding technologies required 452 h/ha in 1992, and will further be reduced by 55 h/ha in 2004, through technology development for minimum or zero tillage, computerized water management system, full mechanization, full automation, among others. For further technology development of direct seeded rice, following premises should be considered; productivity, stability, economic feasibility, applicability, and sustainability. References Choi, H. C., Current achievement and prospect of grain quality improvement in rice breeding. Korean J. Crop Sci. 43 (S), Choi, H. C., Review of achievements in rice research through RDA journal of agricultural science. RDA. J. Agri. Sci. (Special issue), (in Korean) Hong, B. H., H. C. Choi, M. W. Park, Y. H. Hwang and B. H. Lee, Trend and perspectives of crop science in Korea. Trends and perspectives of academic studies in Korea (Physics, Electronic Engineering, Crop Science) Volume I-2, Korean Association of Academic Societies. (in Korean) International Rice Research Institute, Direct seeded flooded rice in the tropics. Los Ban ~ os, Laguna, Philippines. 117 p. 79

20 Rice Culture in Asia International Rice Research Institute, Breaking the yield barrier, Proceedings of a workshop on rice yield potential in favorable environments. Los Ban ~ os, Laguna, Philippines. 141 p. Kim, K. D. and D. G. Park, Trend and prospect of world rice supply and demand. (in Korean) Korea Rural Economy Institute, Agricultural Perspectives 2000, (in Korean) Kim, M. H. and T. H. Kim, Trend and prospect of domestic rice industry in Korea. Agricultural Perspectives 2000, Korea Rural Economy Institute. (in Korean). National Crop Experiment Station, Rice varietal improvement in Korea. 109 p. National Crop Experiment Station, RDA, Infant seedling cultivation of machine transplanted rice Suwon, Korea. 284 p. (in Korean) National Crop Experiment Station, RDA, Direct seeding cultivation technologies of rice Suwon, Korea. 272 p. (in Korean) Park, S. T etc., Practical rice direct seeding technologies. National Yeongnam Agricultural Experiment Station. RDA 330 p. (in Korean) Yoshida, S., Fundamentals of rice crop science. Los Ban ~ os, Laguna, Philippines. 269 p. 80

21 Progress of Irrigation and Drainage in Korean Paddy Field Chapter 7 7 Progress of Irrigation and Drainage in Korean Paddy Field Rice has long been the major food source in Korea. Recent fossil remains in 1991 indicate that rice had been cultivated since B.C History of Korean irrigation and drainage, therefore, cannot be described without explaining the rice cultivation. In this chapter, a brief historical background and major progress of irrigation and drainage with respect to Korean rice paddies, including development of irrigation water, drainage improvement, land consolidation, water management organization and tideland reclamation are described. Korea is facing various challenges in the areas of irrigation and drainage such as environmental issues and water scarcity problems. Some prospects are also presented on such challenges for the future. 7.1 Historical background Seonggu Hong History of irrigation and drainage in Korea may be divided into the following five periods of time: ancient, unified empires, Joseon dynasty, colonization period, and present time since independence. Both ancient remains such as earthen dams and recent tideland reclamation show the remarkable efforts, which have been made to improve agricultural productivity since ancient times Construction of dams by ancient empires (Till 668 A.D.) Agricultural history in Korea indicates that rice culture started in Brunze Age. Since then, management of water resources is presumed to be the major interest of the ancient people and government. Historical records indicate that a number of hydraulic structures were constructed for paddy irrigation. The first earthen dam, Byeokgol-je, with a storage capacity to irrigate paddy field over 10,000 hectares area was constructed in 330 A.D.. It had an embankment over 3,000 meters long with five gates. Two gates were operated as spillways and the others as intakes of irrigation water. Some of the gates are still remained as shown in Figure 7.1. Figure 7.1 Gate pillars of Byeokgol-je 81

22 Rice Culture in Asia More dams were constructed later, including Nul-je and Hwangdeung-je. Only historical records tell that these two dams were over 1,000 meters long. Meanwhile, some of dams such as Uirim-ji, are still in use, which is one of the reservoirs constructed during A.D.. It is quite interesting to see that these dams were constructed in this early period of time. This effort was continued and resulted in significant increases in crop production and more efficient irrigation systems in the following era Land and water resource development by unified empires ( A.D.) During 600 s, Silla dynasty completed the unification of Korean peninsula, which resulted in great changes in the society including agriculture. Dynasty owned lands as was the common practice in most ancient kingdoms. This held true for Goryeo dynasty after Silla. During these periods, more dams were constructed and some old ones were repaired to meet the irrigation requirement for increased paddy fields. The first tidal land reclamation was made near Ganghwa island during this period. Even though this project was initiated for military purpose to construct fortress against Mongolian threat, farmers were allowed to use the reclaimed land to grow crops, mostly rice. Goryeo dynasty ( A.D) strongly encouraged land reclamation for greater crop production. More dams including Namdae-ji in Hwanghae province and Gonggeomji in Sangju were constructed. Waterwheel for irrigation was also introduced from China during this period. Although they drew interests from farmers and scientists, they were not widely used in the nation Systematization of irrigation and drainage ( A.D.) With the development of agricultural technology during Joseon dynasty from 1392, large irrigation programs were systemized to help increase crop production. Many references were published to help farmers. Old dams and canals for irrigation were repaired. In some regions, over 10,000 hectares area of paddies was rearranged into rectangular shape for efficient irrigation and drainage. The world s first rain gauge was invented during this period and installed to collect rainfall data at major stations in each province. During the fifteenth century, dynasty initiated channel improvement for flood control. Channel banks were constructed for river improvements, which resulted in a dramatic increase in rice production. The channel improvement for flood control continued till the end of the dynasty. Scientists during the period of King Sejong also measured water levels in channels for flood control. For this, devices similar to staff gauge were invented and installed in the major streams in the capital city. During this period, a primitive pump was developed for testing. The first field rearrangement was also initiated during this period. A number of crop-related references were published during this period indicating the importance of rice cultivation. More advanced water pumps were developed and used in the fields. A severe drought in 1450 initiated the use of water pumps in irrigation. However, water pumps were not widely accepted in spite of the efforts. 82

23 Progress of Irrigation and Drainage in Korean Paddy Field Chapter 7 In the seventeenth century, double cropping became possible due to the introduction of transplant in rice cultivation. Rice cultivation with transplanting requires more irrigation water and resulted in the construction of more dams. In the beginning of the 18th century, the number of dams was increased to 3,527. The construction skills also were improved. Dynasty s records show detailed descriptions in terms of structural designs such as location and size of spillways. Major hydraulic structures constructed during the 17th century were diversion dams, Eojidun-bo and Gyeong-ugung-bo. These were constructed on both sides of Jaeryeong river in Hwanghae province. Since they were constructed near an estuary, more advanced skills were required. The dams provided irrigation water for over 9,000 hectares of rice paddies. By the mid 1700 s, the number of dams increased up to 3,500. In the early 1800 s, Seo Yugu published a thorough reference on agriculture, in which he emphasized the importance of irrigation and drainage, comparing them to the blood vessel system of human body, and urged for the improvement of irrigation and drainage systems and related technology. He categorized the technology related to irrigation and drainage as follows: 1) Appropriate management of drainage and dredging channels 2) Flood control 3) Construction of dams 4) Management of hydraulic structures such as gates for irrigation and drainage Unfortunately, neither the following government nor scientists continued to implement his idea Forced modernization of irrigation and drainage ( A.D.) Japan s influence on the Korean peninsula began during the 1890 s until complete colonization in In order to solve her food shortage problem, Japan purchased reclaimable land in Korea for cropping at low cost, and began to improve irrigation and drainage conditions. During this period, 520,000 hectares area was developed for crop production. Irrigation system was improved over 335,000 hectares area of paddy fields and about 53,000 hectares was reclaimed for cultivation. Concrete arch dams were also constructed during this period. In addition, the first and only union (association) for irrigation was organized in Even though the main reason for establishing modern hydraulic and irrigation/drainage systems by Japan in Korea is her exploitation of food, modernized facilities and technologies were introduced to the Korean agriculture during this period Achievement and progress since independence ( ) With the independence from Japan, government continued to drive the movement for self-sufficiency in food. Therefore, greater efforts were made for the new development of water resources for irrigation, which resulted in the construction of large-scale dams including several estuary dams. Various international loans were granted for large-scale 83

24 Rice Culture in Asia developments in the agricultural field. Development on groundwater was made for irrigation during 1960 s, particularly in areas where surface water is limited. Asan estuary dam was completed at the end of 1973, providing a total storage capacity of 123,000,000 m 3. For about 20 years from 1970 to 1980 s, six large estuary dams were constructed. The total capacity of these dams was approximately 751,000,000 m 3, providing irrigation water for over 112,000 hectares. In addition, several large dams were constructed for irrigation in inland areas during 1970 s. These dams provided irrigation water to about 35,000 hectares paddy fields. These efforts resulted in a stable irrigation system covering about 76% of paddy fields in the nation. During 1970 s, government recognized that poor drainage affected rice production in some areas and resulted in frequent flood. Therefore, a program was launched for improving nationwide drainage systems, resulting in the drainage improvement in over 100,000 hectares area and is still in progress. These efforts made over a long period of time improved irrigation and drainage systems dramatically nationwide such that 10-year drought design period was applied in planning irrigation systems and self-sufficiency was achieved in rice consumption. The stable and improved irrigation and drainage system seems to be the main driving force in achieving good harvests in rice for recent consecutive years Current issues on irrigation and drainage in Korea Agricultural environment in Korea has been affected by the rapid changes in both social and industrial structures. Water quantity and quality issues are the major problems to be solved. Recent report by Population Action International of United Nations advised on the need to prepare for the scarcity of water resources in Korea. In the near future, Korea is expected to experience serious shortage of water resources from the increasing municipal and industrial water demands competing with the irrigation use. In addition, deterioration of water quality is a limiting factor in irrigation use of water resources. Even though many wastewater treatment facilities have been constructed, they are located mostly in or near large urban areas. Municipal sewage is discharged without appropriate treatment in most rural areas. Thus water quality is seriously deteriorating in streams of rural regions. Particularly, quite a few estuary reservoirs are experiencing rapid deterioration of water quality since they are located downstream. Many of them, in fact, are under eutrophication. Crop production is being affected in fields receiving irrigation water from the eutrophic reservoirs. Therefore, not only the construction of additional treatment facilities, but nutrient management through tertiary treatment and non-point source pollution control should be taken into account in planning water quality management programs. Another issue is the efficient management of irrigation and drainage systems. Several facilities are old and are in need of repairs. Many of them should be replaced or repaired in the near future. Multiple uses of irrigation water may also be included in the management issue. A large number of reservoirs in rural area are constructed solely for irrigation purpose. For a more efficient use of water resources for the future, the functions of irrigation systems should also include such uses as water supply for rural communities, among others. 84

25 Progress of Irrigation and Drainage in Korean Paddy Field Chapter Development of irrigation water Tai Cheol Kim and Joongdae Choi It is a common knowledge that irrigation and drainage technologies play key roles in achieving sustainable development of rice culture General water resources Average annual precipitation of 1,274 mm produces billion m 3 of water, of which an average of 69.7 billion m 3 discharges into rivers and streams at a 55% runoff rate and 57 billion m 3 evaporates or infiltrates as a direct loss (Figure 7.2). However, as far as water shortage is concerned, evaluation of water resources based on the average precipitation is meaningless. An annual precipitation of 890 mm with 20 year drought frequency produces only 88.5 billion m 3 of water, of which 35.4 billion m 3 discharges into rivers and streams showing a 40% runoff rate and 53.1 billion m 3 evaporates or infiltrates. All 35.4 billion m 3 discharged water must be used to meet 37 billion m 3 of water demand in the year This is the reason why Korea is classified into the country group experiencing water shortage. Thus, It would be most favorable to construct dams for storing floodwater in the reservoir. The water demand in 1999 amounted to 30.1 billion m 3, which comprises 6.2 billion m 3 for municipal use, 2.6 billion m 3 for industrial use, 15.4 billion m 3 for agricultural use, and 5.9 billion m 3 for in-stream flow augmentation. The water supply during the same Potential Water Volume billion m3 Atmoshere 55.0 Stream flow 69.7 Flood 46.5 Non-effective 6.0 Non-flood 23.2 Effective 17.2 Evaporation & Infiltration 57.0 Percolation 12.6 Ground Water 2.6 Potential Ground Water Dam supply 12.7 Sea 39.8 Supply 32.5 Domestic 6.2 Industry 2.6 Agriculture 15.4 In-Stream 5.9 Demand 30.1 Figure 7.2 Average water resources and water use in

26 Rice Culture in Asia period was 32.5 billion m 3 consisting of 17.2 billion m 3 of river discharge, 2.6 billion m 3 of ground water, and 12.7 billion m 3 of stored water in the reservoirs. River discharge Since two-thirds of river water flows during the three months of flood season, much of the floodwater ends up in the sea. Thus, on the average, only 23.2 billion m 3 out of 69.7 billion m 3 of river discharge are available for use. River discharge remains low during dry season from October to June, occasionally resulting in severe droughts. On the other hand, river discharge runs high during the wet season from July to September resulting in serious floods. Dam and reservoir storage The 35 large dams providing hydro-power, municipal and industrial water, and flood control have a total water storage capacity of 13.5 billion m 3. Another 17 large dams with a total water storage capacity of 3.9 billion m 3 are under construction. According to long-term plans, 28 multipurpose dams with a total water storage capacity of 4.3 billion m 3 and many agricultural dams with a total storage capacity of 0.8 billion m 3 will be constructed by However, water resource development has become more difficult and several reservoir sites planned are caught in disputes due to increases in construction and compensation costs and strong opposition from the inhabitants and environmentalists. Serious nationwide controversy between the development and conservation of water resources had been on the table for several years. Finally, the policy of water resources was converted from development to conservation, a turning point resulting in the cancellation of the proposed Donggang dam (Figure 7.3) for water supply and flood control. Ground water A total of 3.4 billion m 3 of ground water was withdrawn from 946,000 wells in 1999, resulting in a drop in the ground water table, which in turn is closely related to the discharge of base flow and the water quality in the streams. The ground water use consists of 1.6 billion m 3 for domestic, 1.5 billion m 3 for agricultural, 200 million m 3 for industrial, and 79 million m 3 for other uses, and has been increasing. Approximately 7 billion m 3 of ground water are projected to be mined in 2010 with 4.2 billion m 3 allocated for agricultural use Present status of rural water development Figure 7.3 Proposed Donggang dam site canc-elled due to environmental issues In 1999, at the ICID Meeting in Granada, Spain, irrigation, drainage, and flood control of agricultural lands were declared to be no longer options. They are necessary for feeding billions of people, providing employments to the rural inhabitants, and protecting the environment. ICID stressed that dams have 86

27 Progress of Irrigation and Drainage in Korean Paddy Field Chapter 7 played and will continue to play an important role in the development of water resources, particularly in the developing countries. A balance needs to be found based on the requirements of society, acceptable side effects, and sustainable environment. Irrigation development in Korea is represented by the increare of irrigated paddy field area as shown in Table 7.1. Table 7.1 Paddy field area and irrigated paddy field Year National land area (1,000 ha) Cultivated land area (1,000 ha) Paddy field area Area (1,000 ha) Irrigated Paddy field area , , , ,914 2,144 1, ,927 2,109 1, ,927 1,985 1, ,931 1,945 1, ,937 1,924 1, ,941 1,910 1, ,943 1,899 1, % Investment for rural water development Under the policy framework of Comprehensive plan for rural area development in 1989, comprehensive rural development projects have been executed for agricultural land and water development, improv ement of rural living standards, and off-farm income. A total of US$ 22,434 million (24,677 billion won) was invested under a comprehensive rural develop ment by Of this amount, US$ 18,860 million (84%) was for agricultural land and water development, US$ 2,026 million (9%) for improvement of rural living standards, and US$ 1,547 million (7%) for off-farm income projects (Figure 7.4). Rural water 23% Large scale project 11% Tideland reclamation 6% Land and water 73% Agricultural land and water 84% Present status until1998 US$22.4billion Offfarm7% Rural living standards 9% R&D 2% Paddy consolidation 27% Upland consolidation 3% Disaster Rural settlement prevention Advanced village 6% 10% 2% Industrial Repir Drinking complex 6% 5% 1% Drainage Drought Drinking Rural settlement 4% 1% Advanced 1% 6% Farm tourism 1% village 2% Industrial complex Rural sewage 0% 6% Figure 7.4 Investment for comprehensive rural development up to 1998 Farm road pavement 2% Regional infrastructure 0% Rehabilitation 1% 87

28 Rice Culture in Asia The concept of rural water development, which originally was focused on the supply of irrigation water for rice, has now been broaden to include irrigation water for upland crops, livestock water, and regional water such as domestic, industrial, and in-stream flow augmentation in rural areas. Drought occurs frequently during the rice-transplanting season and/or the rice-flowering season. Irrigation has been generally executed for rice production. A total of 878,490 hectares or 76.2% of the total paddy field area of 1,152,580 hectares are now irrigated, while 274,090 hectares or 23.8% of total still rain-fed as of Only 413,000 hectares or 36% of total paddy field areas are secure from droughts occurring at a 10-year frequency. A total of 15.4 billion m 3 of water for agricultural purpose was withdrawn from reservoirs (5.0 billion m 3 ), pumping stations (1.8 billion m 3 ), headworks (0.8 billion m 3 ), tube wells (1.4 billion m 3 ), other sources (2.3 billion m 3 ), and effective rainfall (4.1 billion m 3 ) in Most agricultural water is used for rice crop with about 500 million m 3 of water applied for upland crops. Figure 7.5 Dae-a dam under re-construction for irrigation, municipal, and small hydro power water Irrigation facilities: reservoir, pumping station, weir, and tube well Major irrigation facilities are reservoir, pumping station, diversion weir, and tube well (Figures 7.5~7.8). A total of 517,100 hectares of paddy fields are irrigated through 18,000 reservoirs, 151,700 hectares through 6,400 pumping stations, 103,100 hectares through 18,320 diversion weirs, 33,100 hectares through 17,130 tube wells, 20,200 hectares through 3,740 infiltration galleries, and 53,300 hectares through other facilities. ICID concluded in its Granada declaration in 1999 that rehabilitation and modernization must result in additional benefits to farmers and be financially viable in that operation and maintenance costs should be at acceptable levels. Figure 7.6 Ganggyeong pumping station with weir to supply irrigation water to 324 hectares of paddy field 88

29 Progress of Irrigation and Drainage in Korean Paddy Field Chapter 7 The main problems of irrigation facilities are old age and small size. Fifty five percent of irrigation reservoirs (Table 7.2) and 31% of pumping stations are older than 50 and 20 years, respectively. In addition 89% of irrigation reservoirs have an effective storage capacity of less than 1 million m 3 (Table 7.3). Thus, irrigation reservoirs have effective storage capacity of 3.1 billion m 3 and normal water surface area of 86,664 hectares in total. The percentage of effective release (actual water release /effective storage capacity) is about 140%. The benefited area from a pumping station is less than 25 hectares on an average. Diversion weir has the function to raise the river water level to the desired height and covers an irrigated area of 6 hectares on the average. The ability of irrigation facilities should be maintained through rehabilitation works. According to the MAF planning, the amount of rural water demand in 2011 is expected to be 17.9 billion m 3, of which 15.5 billion m 3 will be used for agriculture, 0.7 billion m 3 for livestock, and 1.8 billion m 3 for regional water. The existing facilities can only supply 11.2 billion m 3, thus, the remaining 6.7 billion m 3 should be supplied by new irrigation facilities to be built by Figure 7.7 Figure 7.8 A diversion weir to supply irrigation water to paddy field Drilling of tube well for groundwater abstraction during drought period The most critical issue is the construction of new facilities based on with the spirit of environmentally sound and sustainable development. Medium-size multi-purpose dams and reservoirs are advisable due to their many merits. Linked operation of dams in a Table 7.2 Number of irrigation reservoirs with respect to the construction time Year of construction Before ~ ~ ~ ~ ~ ~ 1999 Number 9,706 3,779 2,