Achievements and Advanced Technology of Rice Production in ...9-6)61-90.pdf · for cold tolerance was carried out with the construction of cold-tolerance test nursery. Rice varieties

practices of growers. The priority of rice breeding before the 1st half of 1970’s was onhigh yield and developing resistance to lodging, diseases and environmental stressesrather than grain quality. The focus was then changed to developing resistance to diseaseand insect pests and high grain quality rather than high grain productivity from the 2ndhalf of 1970’s to the 1st half of 1980’s. From the 2nd half of 1980’s, the improvement ofgrain quality was the major objective of rice breeding.

The rice breeding program was not placed in motion during the 2nd half of 1960’s inspite of efforts on improving the resistance to lodging and blast disease, nitrogen respon-siveness, and high yield in japonica rice combinations. Although only 12 new japonicarice cultivars, including selected ones from the introduced Japanese rice varieties, weredeveloped during 1960’s, 11 japonica and 25 Tongil-type high-yielding rice cultivarswere developed through the active international cooperation with IRRI and the adoptionof rapid-generation-advancement breeding system during 1970’s. Hence, self-sufficientrice production was achieved in 1975, and a breakthrough of 5.8 million ton productionof milled rice and the highest yield potential per hectare around the world were attainedin 1977. The first high-quality japonica cultivar resistant to stripe virus disease,‘Nagdongbyeo (Milyang 15)’, was developed and widely distributed in the southern low-land area during that time. In addition, the Tongil-type rice cultivars were considerablyimproved in grain quality and multi-resistance to blast, stripe virus, bacterial blight dis-eases 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-sufficien-cy of rice production during 1970’s~1980’s, their growing area rapidly decreased from1978 after the largest extending to 76% of total rice cultivation area mainly due to theirsusceptibility to cold and relative inferiority in marketing quality as compared with

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Achievements and Advanced Technology of Rice Production in Korea Chapter 6

Table 6.2 Number of newly developed rice cultivar and major achievements incharacter improvement, 1960’s-1990’s

Item

Number of newly developed rice cultivars

Cultivated area of Tongil-type rices (%)Major achievements in character improvement

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)

Semi-dwarf erectleaf, HQ, CT, ST,HY, ADS, AFP

LR, CT, BL, BB,BPH, Short-term

1960’ s

1sthalf

2ndhalf

1sthalf

2ndhalf

1sthalf

2ndhalf

1sthalf

2ndhalf

1970’ s 1980’ s 1990’ s

Japonica 6 6 3 8 21 18 33 37Tongil- type - - 6 19 13 2 3 3Total 6 6 9 27 34 20 36 40

- - 0~23 45~76 27~34 11~22 0~4 -

Japonica BL SV

Tongil- type - Semi-dwarf erectleaf, HY, LR, BL,SV, BPH

BB,CT,BPH,HQ

Super yielding,Aromatic rice

62

Rice Culture in Asia

japonica rices. Fifteen Tongil-type rices and 39 high-quality and high-yielding japonicarice cultivars were developed during 1980’s through the activated japonica rice breedingto 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 yieldingrice project for food processing. During this time, the first high-quality japonica riceusing anther culture technique, ‘Hwaseongbyeo’, was developed. Furthermore, the firstresistant japonica variety to brown planthopper, ‘Hwacheongbyeo’, was developedthrough this haploid breeding system.

In 1990’s, 70 high-quality japonica rice cultivars,including 12 special rices such as glutinous, large grain,chalky endosperm, aromatic, and colored rices weredeveloped. There were also some short-term rice culti-vars adaptable to late transplanting after cash crops andnine cultivars adaptable to direct seeding (Table 6.3).Six Tongil-type rices were developed as high-yieldingaromatic rices and super-yielding rice cultivars duringthe 2nd half of 1990’s.

The japonica rice cultivars developed in 1990s wereimproved, especially in canopy architecture and grain appear-ance, as well as eating quality of cooked rice. They have bet-ter yield potential with enhanced safety in rice cultivation. Inaddition, several special rice cultivars were developed fordiversification of processing utility and for special cultivationsuch as direct seeding or late planting after cash crops.

Table 6.3 Newly developed japonica rice cultivars for special utility and cultivation in 1990’s

Item Newly developed rice varieties

Special rices adaptable to food processing

Short-term rice cultivars adaptable to late planting

Jinbuchalbyeo, Hwaseonchalbyeo, Sangjuchalbyeo, Dongjinchalbyeo (gluti-nous), 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

Rice cultivars adaptable to direct seeding

Nonganbyeo, Juanbyeo, Ansanbyeo, Donganbyeo, Daesanbyeo,Gwanganbyeo, Hoanbyeo, Nonghobyeo, Junganbyeo

Figure 6.5 The first Tongil-type rice cultivar‘ Tongil’developed from a three-way cross among two semi-dwarfindica and japonica rice varieties

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6.2.2 Progress in rice breeding systemand techniques

The conventional breeding systems suchas pedigree and bulk method mainly used inhandling the japonica rice materials weremodified into general breeding systemsaccompanying the rapid generationadvancement (RGA) scheme utilizing thegreenhouse (Figure 6.6) or IRRI field dur-ing winter season. Thus, changes weremade to the real rice breeding works tointroduce useful characteristics from tropi-cal indica rice from the 2nd half of 1960’s.Several rice breeding mutations throughirradiation were attempted during this time,but were terminated with almost no practi-cal outcomes.

The RGA rice breeding system and rapidextension of Tongil-type rice cultivarsthrough seed multiplication in IRRI fieldduring winter were actively carried out dur-ing 1970’s since the development of thefirst Tongil-type rice cultivar ‘Tongil’ in1971.(Figure 6.5)

Also, the breeding efficiency was largelyenhanced through the continuous improve-ment in testing techniques for evaluatingthe grain quality and resistance to diseaseand insect pests during this time.

The haploid rice breeding utilizing the anther culture technique (Figure 6.7) was esta-blished for japonica rice since the first varietal development of ‘Hwaseongbyeo’ using thissystem in 1986. The rice breeding period was shortened to 5~6 years by this technique.A total of15 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) wasinitiated 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 amilled rice yield of 7.3~8.3 t/ha in 1989. However, they were not distributed to the farmersdue to difficulties in hybrid seed production and poor acceptance. In addition, a recurrentpopulation improvement breeding scheme using genetic male sterility (GMS) was operatedto enhance the opportunity of desirable recombination by breaking undesirable characteristiclinkages and accumulate useful genetic factors related to diseases and insect pests by sup-porting the existing conventional pedigree breeding system.

Figure 6.6 Greenhouse with RGA rice breeding system

Figure 6.7 Rice breeding through anther culture technique(callus induction, differentiation of green plant,diploid & haploid rice plants)

The establishment of testing systemand effective selection of breeding linesfor cold tolerance was carried out withthe construction of cold-tolerance testnursery. Rice varieties were subjected toa cold-water irrigation (17℃) drainedfrom Soyang dam in Chuncheon since1979 (Figure 6.9). This facility has beenutilized by IRRI as the international ricecold-tolerance test nursery since 1975.For the effective in situ selection andshuttle breeding for salinity and coldtolerance, Namyang and Gyehwa Sub-stations were established in western-coastal reclaimed area, while Jinbu,Unbong, Sangju, and Yeongdeok Sub-

stations were constructed in high altitudeareas of north eastern and southern, mid-mountainous, and eastern-coastal coldareas, respectively, from 1978 to 1982.

The establishment of embryo rescuetechnique was realized to obtain aninterspecific hybrid between differentgenomic wild species and cultivarsand to introduce resistant genesagainst diseases and insect pests fromwild rice species to cultivars viarecurrent backcrossing during 1990’ s.Furthermore, the basic techniques to

64


Figure 6.9 Cold tolerance test nursery with cold-water flowingsystem in Chuncheon

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 methodsMutation breeding by irradiation

1970’ s Development of ‘Tongil’ cultivar from a three-way remote cross between semidwarfindica and japonica ricesIntroduction of rapid generation advancement (RGA) scheme in conventional ricebreeding systemEstablishment of effective testing & evaluation technologies for resistance to pests andgrain quality

1980’ s Practical settlement of anther culture technique in japonica rice breedingDevelopment of Tongil-type hybrid rices using cytoplasmic- genic male sterility (CGMS)Improvement of cold & salinity tolerance testing systemDevelopment and operation of recurrent population improvement breeding schemeusing genetic male sterility (GMS)

1990’ s Establishment of embryo rescue technique for interspecific hybridization between wildrice species and cultivarsDevelopment of basic technique for molecular breedingDriving of effective rice breeding system for direct seedingMutation breeding for high grain quality and diversification of food-processing utility

Figure 6.8 Reduction of breeding period by rapid generation advancement and anther culture technique.

1 2 3 4 5 6 7 8 9 10 11 12 13 14

* Hybridization & anther culture

Breeding system

Conventionalpedigree method

Rapid generation

advancement

Anther culture

technique

Generation advancement (years)

Hybri-dization

(H)

Pedigree nursery(P)

Yield trial(YT)

Localadaptability

test(LAT)

Pilotfarming

test(PFT)

H P YT LAT

PFT

HAC* YT LAT PFT

ensure the practical utilization of biotechnologies in rice breeding were developed, andstudies on the improvement of evaluation techniques and breeding systems were activelypursued for improving the adaptability to direct seeding and high-quality or diversifica-tion of food-processing utility in recent years (Table 6.3 & 6.4) (NCES 1990).

6.2.3 Achievements in the improvement of major agronomic characteristics

Milled rice yield of newly developed cultivars during 1990’s increased by about 43% inhigh-quality japonica rices and about 41% in Tongil-type rices as compared with those ofjaponica rices during the first half of 1960’s and those of Tongil type rices during the first halfof 1970’s, respectively (Table 6.5 & Figure 6.10) (Choi 1999).

In particular, the japonica rice cultivars were largely improved in lodging tolerance throughthe introduction of semi-dwarf gene, stiff culm, and erect plant type since 1980. The maturityof rice cultivars was also diversified from extremely early to medium-late maturing since1970’s (Figure 6.11), which largely contributed to the increasing of the grain yield in alpineand mid-mountainous areas, as well as, in lowland areas.

The first japonica rice cultivar resistant tostripe virus disease, ‘Nagdongbyeo’ wasdeveloped in 1975 and since then, severalother japonica rice cultivars resistant to thestripe virus disease were continuously devel-oped. In addition, high-quality japonica ricecultivars were extensively improved forresistance to major diseases and insect pestssince 1980. The first resistant cultivar tobrown planthopper ‘Hwacheongbyeo’ wasdeveloped through the anther culture haploidbreeding during this time.

8.0

7.0

6.0

5.0

4.0

3.0

1960 1970 1980 1990 2000

Year

Mill

ed ri

ce y

ield

(t/h

a)

Tongil-typeJaponica

65


Table 6.5 Changes in milled rice yield of developed cultivars during the last four decades

Ecotype Item

Japonica Average (t/ha) 3.77 3.89 4.68 4.34 4.91 5.02 5.02 5.40(Index) (100) (103) (124) (115) (130) (133) (133) (143)Range (t/ha) 3.70 3.58 - 4.12 4.31 4.78 4.61 4.98

~3.85 ~4.01 ~4.74 ~5.28 ~5.34 ~5.31 ~5.96Tongil- Average (t/ha) - - 4.91 5.01 5.62 - 6.11 6.94Type (Index) - - (100) (104) (114) (124) (141)

Range (t/ha) - - 4.49 4.39 4.96 - 4.93 6.14~5.54 ~5.81 ~6.05 ~6.77 ~7.41

1960’ s

1sthalf

2ndhalf

1sthalf

2ndhalf

1sthalf

2ndhalf

1sthalf

2ndhalf

1970’ s 1980’ s 1990’ s

Figure 6.10 Changes in milled rice yield (t/ha) of newly developed rice cultivars during the last four decades

The Tongil-type rice cultivars werealso rapidly improved for multi-resis-tance to major diseases and insect pests,and soon after a severe occurrence ofneck blast in 1978, new blast-resistantvarieties were developed (Table 6.6).

Japonica rice cultivars were consider-ably improved in terms of lodging andcold tolerance, and the Tongil-type ricecultivars were relatively improved interms of cold tolerance, adaptability tolate planting, and grain shattering (Table6.7).

Although the development of short-term early rice cultivars started fromthe late 1970’s, the first short-term rice

cultivar, ‘Keumobyeo’, suitable for ext-remely late transplanting after cash crop cultures,was developed in 1988. Subsequently several short-term rices such as ‘Keumobyeo 1’,‘Keumobyeo 2’, ‘Geurubyeo’, and ‘Mananbyeo’ were continuously developed during1990’s.

66


Japonica Jinheung 1962 MS MS S S S S S S SNagdongbyeo 1975 S MS S S S MR S S SSeomjinbyeo 1982 M MR R S S MR S S SPalgongbyeo 1986 M MR S S MS R M M SHwacheongbyeo 1986 MR MR R S S MR S S MRHwayeongbyeo 1991 M MR R R R R S S S

Tongil- Tongil 1971 M MS R MR S R S S SType Milyang 23 1976 M MS S S S R MR S S

Milyang 30 1977 MR M R MR S R MR MS RTaebaegbyeo 1979 R R MR MR MR R MR M SSamgangbyeo 1982 MR R R MR MR R MR M RNamyeongbyeo 1986 MR R R R R R MR MR SAndabyeo 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.

Ecotype Cultivar Bredyear

Leaf Neck K1 K2 K3 SV DV BSDV

Blast Bacterial blight Virus BrownPlant-

hopper

Table 6.6 Improvement of resistance to major diseases and insect pests in newly- developedjaponica and Tongil-type rice cultivars

Figure 6.11 Varietal variation of newly developed rice cultivars in maturity since 1958.

Sep. 01

Aug. 25

Aug. 20

Aug. 15

Aug. 10

Aug. 05

Jul. 30

Jul. 25

1960 1970 1980 1990 2000Year

Hea

ding

dat

e

Tongil-typeJaponica

The grain quality of Tongil-type rice cultivars was rapidly improved in terms of eatingquality of cooked rice by reducing the amylose content of endosperm and was steadilyimproved in terms of marketing quality through the selection toward clear and short grainduring 1970’s-1980’s. Through the concentration of steady efforts to grain qualityimprovement of Tongil-type rices, short, clear, and low-amylose rice cultivars, ‘Jung-wonbyeo’ and ‘Chilseongbyeo’, were developed in 1984. The grain quality of japonicarice cultivars has been improving in both grain appearance and palatability of cooked ricesince 1980 (Table 6.8) (Choi 1998).

The recent breeding efforts on diversification of food-processing utility had realizedthe development of special rice cultivars such as large kernel, chalky endosperm, aromat-ic, and colored rices (Table 6.9).

6.2.4 Prospect of rice varietal improvement

The world rice production in 2010 is projected to be about 445 million tons harvestedfrom 154 million hectares of cultivation acreages, and the ratio of stock rice is expectedat about 12~13% of consumption amount. The domestic rice production in 2004 is alsoexpected to maintain self-sufficiency and about 17% of stock rice ratio (Kim & Park2000, Kim & Kim 2000).

In Korea unstable environmental conditions in rice production may continue due to thegreenhouse effect and unexpected local meteorological disasters. In addition, deterioration

67


GALT: Germination ability at low temperature, AHR: Abnormal-heading responsiveness, GYLP: Grainyield 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: salinitytolerance, GS: grain shattering, Ha: hard, E: easy, ME: medium easy

Japonica Jinheung 1962 R R R M IS H MS M HaNagdongbyeo 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 EType Milyang 23 1976 M S MS S IS L R S “

Pungsanbyeo 1980 MR MS M M IS M R S MESamgangbyeo 1982 M S MR M IS M MR S “

Ecotype CultivarBredyear

GA-LT

Cold tolerance Adaptability in late planting

AHR GYLP

LT ST GSSeed-ling

stage

Head-ing

delay

Spikeletsterility

Table 6.7 Improvement of tolerance to various environmental stresses in newlydeveloped japonica and Tongil-type rice cultivars

68


of paddy soil may be more severe with the increased air and water pollutions, and theshortage of irrigation water will become more serious in the future. Greenhouse effectwill also result in an increase in the occurrence of diseases. The pressure on the openingof rice market from some export countries will be stronger, and the socioeconomic situa-tion will also be unfavorable for maintaining self-sufficiency in domestic rice supply anddemand.

Table 6.8 Improvement of grain quality in Tongil-type and japonica rice cultivars since 1970

Japonica Pungok 1936 5.16 2.91 2.06 1.77 1/1 L 18.2 7.6 FGJinheung 1962 4.88 2.58 2.18 1.89 1/1 “ 19.8 7.7 FGDongjinbyeo 1981 5.05 2.94 2.00 1.72 0/1 “ 18.0 7.3 GIlpumbyeo 1990 4.96 2.71 2.07 1.83 0/1 “ 18.9 6.7 EAverage 5.01 2.78 2.07 1.80 - - 18.8 7.3

Tongil- Tongil 1971 5.54 2.62 1.93 2.24 0/5 ML 23.3 8.7 Atype Milyang 23 1976 6.15 2.55 1.97 2.41 1/0 “ 19.1 7.9 FG

Samgangbyeo 1982 5.51 2.48 1.88 2.22 1/2 “ 17.4 7.6 FGJungwonbyeo 1984 5.10 2.68 1.79 1.90 1/1 “ 16.7 7.8 GAverage 5.57 2.58 1.89 2.19 - - 19.1 8.0

GT: gelatinization temperature, WC/WB: white core/white belly, A: acceptable, FG: fairly good, G: good, E: excellent

Ecotype CultivarBredyear

Brown rice (mm) Chalki-ness

(WC/WB)(0-9)

GTAmy-lose(%)

Pro-tein(%)

Palata-bility ofcookedrice

Length Width Thick-ness

L/Wratio

Table 6.9 Development of special rice cultivars suitable for food-processing

CultivarBredyear

Heading date

Culmlength(cm)

Milled rice yield

(t/ha)

1,000-kernel

weight (g)

L/Wratio

Chalk-iness

(WC/WB)(0-9)

Color ofseed coat

Aroma(0-9)

Amy-lose(%)

Daeribbyeo 1 ‘93 Aug.15 88 4.45 34.8 1.94 1/0 YW 0 19.5Hyangmibyeo 1 ‘93 Aug.15 72 4.93 20.6 2.46 1/1 “ 5 18.3Hyangnambyeo ‘95 Aug.11 82 5.03 21.3 1.81 0/0 “ 3 17.7Hangmibyeo 2 ‘96 Aug. 4 77 6.14 22.8 2.44 1/2 “ 3 19.0Yangjobyeo ‘94 Aug.14 71 5.11 25.4 1.78 7/0 “ 0 20.2Aranghyang ‘97 Aug.13 88 5.37 20.5 1.90 - “ 3 0.0chalbyeoHeugjinjubyeo ‘97 July 25 80 4.05 17.0 2.22 - BP 1 15.1Heugnambyeo ‘97 Aug.13 73 4.97 23.5 2.14 - “ 1 16.7Seolhyang ‘99 Aug. 8 89 5.23 24.2 2.10 - YW 3 0.0chalbyeo

L/W ratio: length/width ratio of brown rice, YW: yellowish white, BP: blackish purple

Accordingly, the rice breeders must come to terms with the outlook of our rice industryand be ready for the expected changes in environmental and socioeconomic situations.Recently, an effective selection and introduction of useful agronomic target genes weremade possible through the utilization of DNA markers associated with target genes andbiotechnological method of gene transformation after the biochemical pathway andmechanism of the characteristic expression and relevant genetic factors were elucidated.In addition, the possibility of desirable recombination and enhancement of useful expres-sion will be gradually realized through the identification of target gene locus, genecloning, and transformation. The genetic variation of rice breeding materials will bediversified through the introduction of various useful alien genes using biotechnologicalprocedures in the future, which may be helpful for increasing the stability of self-suffi-cient rice production and enhancing the competitiveness of our rice products in the worldtrade market.

The yield potential in milled rice is expected to be increased to 6.5 t/ha in high-qualityjaponica rice and 10.0 t/ha in super-yielding rice cultivar by 2010. The grain quality willbe improved continuously toward high marketing quality of milled rice and excellentpalatability of cooked rice. Wider diversification of morphological and physicochemicalcharacteristics of rice grain for various food-processing utilities and hygienic functionsthrough chemical mutation and biotechnological genetic control will also be performed.Specifically, breeding efforts on the enhancement of hygienic functions in rice will leadto the development of diversified special rices, such as a low allergen rice for atopic der-matitis patients, low protein rice for nephrism patients, high lysine or high sulfur-contain-ing amino-acids rice, high procarotenoid rice, high fiber rice, giant embryo rice, amongothers (Choi 1998).

Complex resistance to major pests and environmental stresses suitable for each relevantregion will be gradually strengthened using introduced rice germplasm from wild speciesand through the countermoving breeding against global climatic changes in the agricul-tural environment.

To increase the utilization of paddy field, diversification of short-term rice varietiesadaptable to various cropping system will be developed continuously not only to takeadvantage of the wide adaptability with less variation of grain yield but to be more adapt-able to extremely late planting through the appropriate combination of basic vegetativephase and relative photo- and thermo-insensitiveness in flowering response.

The varietal improvement of direct seeded rice for low-cost and labor-saving cultiva-tion will continue via mass selection under dry or water seeding conditions, and screen-ing of germination ability and shoot emergence under soil at low temperature, lodgingtolerance, and adaptability to dense planting.

6.3 Mechanization of rice production

Rapid economic growth has influenced the structure of agriculture in Korea. The farm-ing population which was 37.5, 21.1, and 9.7% in 1975, 1985, and 1997, respectively andis expected to decrease continuously.

69


70


Yield in polished rice has increased from 3.8 t/ha in 1975 to 4.5 t/ha in 1985 and 5.22t/ha in 1997. Total rice production in 1997 was about 5.8 million tons, maintaining self-sufficiency. However, increasing farm wages and decreasing availability of farm laborhave resulted in much higher costs of production.

One of the most significant changes in rice production in recent years is the technologydevelopment of direct seeding method. Until early 1980’s, the ultimate target of rice cropwas the quantitative relation and the primary concern was maximum harvest with maxi-mum input. However, much emphasis has been recently placed on finding ways to reducethe production inputs and achieve greater profitability. Thus, technologies of direct seed-ing and machine transplanting of infant seedlings are the prime concerns.

Since 1985, direct seeding and machine transplanting infant seedling with have activelybeen studied as remarkable labor-saving technologies based on the research conducted bythe National Crop Experiment Station (NCES), National Honam Agricultural ExperimentStation (NHAES), National Yeongnam Agricultural Experiment Station (NYAES), nineProvince Agricultural Research and Technology Centers (ADTEC), and leading farmers.

6.3.1 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 byhand transplanting. Rapid industrial growth has led to the outflow of labor force fromrural to urban areas, and farmers were faced with the need of labor-saving. Thus, amachine transplanter was introduced to solve this situation.

From 1978, a machine transplanting method using semi-adult seedling with 35 daysnursery period was introduced. In 1990, another machine transplanting using infantseedling with only 8 to 10 days old was developed as a labor-saving technology.Subesquently, techniques for machine transplanting cultivation were developed and arecompletely established at present. Thus, in 1999, the machine transplanted paddy occu-pied 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 graduallyestablished through the develo-pment of a new machine, herbicide and cultivation technique,

and the cultivation area of direct seed-ing showed an increasing trend. By1995, the area of direct seeding culti-vation has been increased up to117,500 hectares, 11.1% of the totalpaddy fields of Korea, among whichdirect seeding on dry paddy was 6.4%,and direct seeding on flooded paddywas 4.7%. The area of direct seeding isexpected to increase through improve-ments and counter plans for the prob-lems of cultivation technique in thefuture.Figure 6.12 Changes in rice cultivation technologies

Hand transplanting Machine transplanting

Direct seeding

Year

100

80

60

40

20

0

’ 77 ’ 79 ’ 81 ’ 83 ’ 85 ’ 87 ’ 89 ’ 91 ’ 93 ’ 95 ’ 97 ’ 99

Pro

porti

on o

fcu

ltiva

tion

area

(%)

6.3.2 Infant-seedling machine transplanting

The development of a raising method for infant rice seedling (8 to 10 days old) is animportant technology for labor-saving and cost-reduction in rice production due to veryshort nursery period compared with semi-adult seedling (35 days old), which is the con-ventional seedling raising method for machine transplanting in Korea. The raisingmethod of infant rice seedling is very similar with that of the semi-adult seedling exceptfor the seeding rate and nursery period.

In 1997, the machine transplanted area wiht semi-adult seedling occupied 67.1% andthat with infant seedling occupied 21.2% of the total paddy area. Comparative character-istics between infant and semi-adult seedlings are presented in Table 6.10.

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 factory-style multi-layer culture of infant seedling was developed by the National CropExperiment Station. This automatic raising seedling facilities composed of all raisingseedling processes from seeding to the last step of raising seedling. This new method ofraising seedling on the shelves has ten tiers at 30 cm interval and can grow 8 to 10 daysinfant seedlings.

71


Items Infant seedling Semi-adult seedling

Nursery period (days) 8~10 30~35Seeding rate (g/tray) 200~220 110~130Leaf number at transplanting 2.5~3.0 3.5~4.0Seedling height (cm) 5~8 15~18Amount of remained endosperm (%) 30~50 0Seed trays needed (no./ha) 150 300

* Size of seedling tray: 30 x 60 x 3cm

Table 6.10 Comparison between infant and semi-adult rice seedling

72


6.3.3 Direct seeding cultivation technologies

Essentially, there are two methods of direct seeding in rice, dry and wet seeding, basedon the physical condition of the seedbed and seeds. In Korea, wet seeding is furtherdivided into two methods: wet drill seeding and water seeding. Recently, a corrugated-furrow drill seeding was developed. In 1997, the total direct seeded area was 110,600hectares, which is 10.5% of the total rice paddy, 1,052,000 hectares (Table 6.11).

Yield stability in direct seeded rice is relatively low compared with the transplantedrice due to several major problems. A general chart of technology development for theproduction stability of direct seeded rice in Korea is shown in Figure 6.13.

Direct seeding method

Dry seeded rice 5.4 57.2 (51.7%)Wet seeded rice 5.1 53.4 (48.3%)- Wet drill seeding 2.3 24.3 (22.0%)- Water seeding 2.8 29.1 (26.3%)

Total 10.5 110.6 (100%)

% of DS paddyto the total area

Area of direct seededpaddy (x1,000 ha)

* Total area of rice paddy in Korea, 1997 was 1,052,000 ha

Table 6.11 Major direct seeding (DS) methods and the area of direct seeded rice in Korea, 1997

Production Stability of Rice

Figure 6.13 Technology development for production stability of direct seeded rice in Korea

Cultivar development

Seedling stand stability Lodging prevention Weed control

Establishment ofcultural practices

Research oncultivation environment

∙Low temp. germinability

∙Low-tillering, large panicle plant type

∙Early maturity∙Lodging resistance

∙Seeding methods∙Seeding time∙Fertilizer application∙Water management

∙Soil management∙Integrated pest

management∙Water pollution∙Ecosystem change

∙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

Technology development for increasing the production stability in direct seeded ricerequires the establishment of proper cultivation technology, cultivar development adapt-able to direct seeding environments, improvement of major problems such as unstableseedling stand, easy lodging, difficult weed control, among others, and also fundamentalresearch for direct seeding cultivation, including soil management and integrated pestmanagement.

Dry seedingIn dry seeded rice, there are two different seeding methods, flat drill seeding and high-

ridged drill seeding. Generally, conventional method of flat drill seeding having six rowsuses dry seeds and soil cover after seeding, with irrigation at 3rd leaf stage. Flat drillseeding has higher working efficiency compared with high-ridged drill seeding for seed-ing and harvesting operations. However, this seeding method is unstable under severe cli-matic conditions such as heavy rain or severe drought.

For high-ridged dry drill seeding, a drill seeder makes small canals of 25 cm wide and12 cm depth in the center with every 1.5 meter interval. This canal can be used as irriga-tion or drainage canal depending on the soil moisture condition. The standard culturaltechnology of dry seeded rice is shown in Table 6.12.

Land leveling in direct seeding cultivation is one of the most important cultural prac-tices for improving seedling establishment, and water, nutrient, and weed managements.A laser leveling system was introduced to arrange uniform land leveling for both dry andwet seeding cultivations.

With the introduction of laser scraper, a precise leveling was available with only 3.0cm difference between the high and low portions in the field, while a conventional rota-vator revealed about 8.0 cm of level difference (Table 6.13).

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Items Cultural practices

Tillage Land levelingSeeding method

Seeding timeSeeding rateSeedsOpt. seedling standFertilizer

Water managementWeed 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/㎡- N - P2O5- K2O = 150 - 45 - 57 kg/ha

Nitrogen split: Basal-5th leaf stage - Panicle initiation= 40 - 30 - 30%

- 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

Table 6.12 Standard cultural technology of dry seeding

Wet drill seedingWet drill seeding is commonly prac-

ticed for flooded and puddled lands fortimely crop establishment (Figure6.15). Sprouted seeds are sown on orbelow the puddled soil surface. A wetdrill seeding was developed to improvethe problems of water seeding such asunstable seedling stand and lodging. Ariding-type wet drill seeder with sixfurrow openers presses the hardenedpaddy soil to make furrows, which are5 cm in width and 4 cm in depth.

The standard cultural practice of wetdrilling seeding is shown in Table 6.14.

For the management of diseases andinsect, super-wide sprayer was introduced.The maximum distance of chemicalspray is about 80 meter (Figure 6.16).Therefore, the total labor hours for chem-ical spray could be reduced to 10% ofthat by a conventional power sprayer(Table 6.15).

Water seeding Water seeding is a technique in which

pre-germinated seeds (2~3 days soakingand 24 h incubation) are sown in stand-ing water. Seeds must be heavy enoughto sink in standing water to makeanchorage at the soil surface. Water

seeding is done mostly by motorized sprayers.

Seedling establishment is very poor. Plant anchorage is weak, leading to lodging at maturi-ty. Higher seedling stand and lodging tolerance combined with stiff culm and deep rootinghabit are required.

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Table 6.13 Effect of land leveling by laser scraper based on the difference of land level between high and low portions of paddy

Laser scraper 10.4 <3.0 12.7 <3.0Conventional rotavator 10.4 8.4 12.7 7.8

* Both the widths of laser scraper and conventional rotavator are 3.2m

Treatment Dry seeding

Before After Before After

Wet seeding

Difference of land level (cm)

Figure 6.15 Wet drill seeding by a transplanter-attachable drillseeder

Figure 6.14 Leveling by a laser leveling system

Because water seeding is the most effectivelabor-saving technology, the area of waterseeding will increase with the development ofvarieties with good seedling establishmentand lodging tolerance.

Seosan tideland reclamation area, about10,000 hectares in the western coast ofKorea was developed as paddy fields. From1986, the cultural practice of direct seededrice including application of agro-chemicalswas performed using an aircraft as inCalifornia, USA.The standard culturalmethod of water seeding is given in Table6.16.

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Sprayer Labor required to operate

Total labor hours (minute/ha)a sprayer (person/ha)

Superwide sprayer 2 26 (10%)Conventional power sprayer* 5 255 (100%)

Table 6.15 Effect of superwide sprayer for controlling pest on labor-saving

*Conventional power sprayer attached to a tractor


- 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/㎡- N - P2O5- K2O = 110 - 45 - 57 kg/haNitrogen split: Basal - 5th leaf stage - Panicle initiation

= 40 - 30 - 30%- 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)

TillageLand levelingSoil hardeningSeeding methodSeeding timeSeedsSeeding rateOpt. Seedling stand Fertilizer

Water management

Weed control

Table 6.14 Standard cultural technology of wet drill seeding

Figure 6. 16 Pest control by a super wide sprayer

Corrugated-furrow seedingA 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 pre-pared under dry field condition during final land leveling operation with corrugated riceseeder attached to the back of the rotavator at the same time with basal fertilizer incorpo-ration. However, for the dry seeding method, seeding operation is done simultaneouslywith corrugated-furrow preparation. In water seeding method, corrugated furrows are ini-tially prepared and then water is irrigated into the field. Subsequently, rice seeds arebroadcasted under flooded condition using a motorized seed sprayer.

The standard cultural method of corrugated-furrow seeding is shown in Table 6.17.

Effective weed control in direct seedingOne 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 theeffective weed control technology.

Weed growth is strongly affected by cultivation method. Weeds in direct seedingincreased 2 to 3 times as compared with transplanting. When the seedlings were not sub-jected 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 transplantingcultivation. In Korea, weed control is mainly dependent on herbicide application.

For dry seeded rice, two systematic herbicide applications are recommended; one dur-ing 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



- Once or twice rotavation under flooded paddy- Laser leveling in dry or wet paddy condition- Hardening under flooded condition for 1-3 days afterharrowing

- 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/㎡- N - P2O5 - K2O = 110 - 45 - 57 kg/haNitrogen split: Basal - 5th leaf stage - Panicle initiation= 40 - 30 - 30%

- 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)

TillageLand levelingSoil hardening

Seeding methodSeeding timeSeedsSeeding rateOpt. seedling standFertilizer

Water managementWeed control

Table 6.16 Standard cultural technology of water seeding

to applying herbicide. Herbicidal efficacy was the greatest at the application of 12~15DAS (just after rice emergence). Recommended herbicides are given in Table 6.18.

For wet-seeded rice, the success of effective weed control practice mostly depends ongood tillage operation, particularly on harrowing operation and the degree of root anchorwhen first herbicide is applied. One-shot herbicides of sulfonylurea mixture are currentlyrecommended at 8~10 DAS (Table 6.19).

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Period Application time Herbicides

Table 6.18 Recommended herbicides and their application systems in dry-seeded rice

Dry

Flooded

* DAS: Days After Seeding

3~5 days after flooding

�Pyrazosulfuron-ethyl/Molinate�Bensulfuron-methyl/Dimepiperate�Butachlor�Thilbencarb

12~15 DAS(after rice emergence)

ButachlorThiobencarb

. Propanil + PendimethalinMolinate


- 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 1 - 20- 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 con-

ventional water management- N - P2O5 - K2O = 110 - 45 - 57 kg/haNitrogen split: basal at seedling emergence

- 6th leaf stage-panicle initiation = 40 - 30 - 30%- Herbicides application: pyrazosul./moli.,cyhalo./azimsul./moli. at 1.5~2.0 leaf stage of rice

TillageMaking corrugated furrowSeeding method

Seeding timeSeedsSeeding rateWater management

Fertilizer

Weed control

Table 6.17 Summary of corrugated - furrow seeding method

6.3.4 Labor-saving effect of direct seeding

The competitiveness in rice production should be increased through the introduction oflabor-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 isexpected 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 seed-ing. This is about 30% lower than 357 h/ha of machine transplanting with aged seedlingwhich is the conventional machine transplanting method. Direct production cost of riceexcluding land service charge etc. was reduced by 21% in dry seeding and 16% in wetseeding, as compared with that of machine transplanting with semi-adult seedling (Table6.20).

6.3.5 Research strategies and prospect of direct seeding

A long period of time is required to establish the technical system of direct seeding cul-tivation due to its various cultivation types. Future research strategies on direct seeding inKorea should be based on the followings:∙Improvement of specific rice varieties for different direct seeding methods

78


Application time Herbicides

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

- Pyrazosulfuron-ethyl/Molinate- Bensulfuron-methyl/Dimepiterate- Azimsulsuron/Molinate- Cyhalofop-Molinate/Azimsulfuron- Imazosulfuron/Mefenacet/Dymron- Stem F-34- Bentazon, 2.4-D

Table 6.19 Recommended herbicides and their application time in wet- seeded rice

Items

* US$ 1 = 951 Won (1997)

Machine transplanting

Semi-adultseedling

Infantseedling Dry seeding Wet seeding

Direct 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)

Table 6.20 Labor hours and rice production cost of machine transplanting and direct seeding

∙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 typesof direct seeding methods such as dry drilling seeding, wet drilling seeding, water seed-ing, and corrugated-furrow seeding. RDA has already initiated the development of directseeding methods via minimum or zero tillage cultivation.

Even though these direct seeding methods are not yet well established, the direct seed-ing acreage has been rapidly increasing since 1992, and was the largest in 1995 at117,500 hectares but decreased to about 73,700 hectares in 2000.

Potential paddy field area of direct seeding in Korea is about 70% of the total rice fieldarea. The government further expects that the direct seeding area will increase by 40 to50% in the near future. Grain yield in milled rice was 4.45 t/ha in 1995, and this isexpected to further increase by 5.15 t/ha in 2004, through improvement of rice varietiesand cultivation technology for direct seeding.

Labor hours via direct seeding technologies required 452 h/ha in 1992, and will furtherbe reduced by 55 h/ha in 2004, through technology development for minimum or zerotillage, computerized water management system, full mechanization, full automation,among others. For further technology development of direct seeded rice, followingpremises should be considered; productivity, stability, economic feasibility, applicability,and sustainability.

References

Choi, H. C., 1998. Current achievement and prospect of grain quality improvement inrice breeding. Korean J. Crop Sci. 43 (S), 1-10.

Choi, H. C., 1999.Review of achievements in rice research through RDA journal ofagricultural science. RDA. J. Agri. Sci. (Special issue), 52-62. (in Korean)

Hong, B. H., H. C. Choi, M. W. Park, Y. H. Hwang and B. H. Lee, 1999. Trend andperspectives of crop science in Korea. Trends and perspectives of academic studies inKorea (Physics, Electronic Engineering, Crop Science) Volume I-2, 219-338. Korean Association of Academic Societies. (in Korean)

International Rice Research Institute, 1991. Direct seeded flooded rice in the tropics.Los Ban~os, Laguna, Philippines. 117 p.

79


International Rice Research Institute, 1993. Breaking the yield barrier, Proceedingsof a workshop on rice yield potential in favorable environments. Los Ban~os, Laguna,Philippines. 141 p.

Kim, K. D. and D. G. Park, 2000.Trend and prospect of world rice supply anddemand. (in Korean)

Korea Rural Economy Institute, Agricultural Perspectives 2000, 147-163. (in Korean)

Kim, M. H. and T. H. Kim, 2000. Trend and prospect of domestic rice industry inKorea. Agricultural Perspectives 2000, 165-177. Korea Rural Economy Institute.(in Korean).

National Crop Experiment Station, 1990.Rice varietal improvement in Korea. 109 p.

National Crop Experiment Station, RDA, 1992. Infant seedling cultivation ofmachine transplanted rice Suwon, Korea. 284 p. (in Korean)

National Crop Experiment Station, RDA, 1997. Direct seeding cultivation technolo-gies of rice Suwon, Korea. 272 p. (in Korean)

Park, S. T etc., 1999. Practical rice direct seeding technologies. National YeongnamAgricultural Experiment Station. RDA 330 p. (in Korean)

Yoshida, S., 1981. Fundamentals of rice crop science. Los Ban~os, Laguna, Philippines.269 p.

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81

Progress of Irrigation and Drainage in Korean Paddy Field

7 Progress of Irrigation and Drainage in Korean PaddyField

Rice has long been the major food source in Korea. Recent fossil remains in 1991 indi-cate that rice had been cultivated since B.C. 2300. History of Korean irrigation anddrainage, therefore, cannot be described without explaining the rice cultivation. In thischapter, a brief historical background and major progress of irrigation and drainage withrespect to Korean rice paddies, including development of irrigation water, drainageimprovement, land consolidation, water management organization and tideland reclama-tion are described. Korea is facing various challenges in the areas of irrigation anddrainage such as environmental issues and water scarcity problems. Some prospects arealso 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 peri-ods of time: ancient, unified empires, Joseon dynasty, colonization period, and presenttime since independence. Both ancient remains such as earthen dams and recent tidelandreclamation show the remarkable efforts, which have been made to improve agriculturalproductivity since ancient times.

7.1.1 Construction of dams by ancient empires (Till 668 A.D.)

Agricultural history in Korea indicates that rice culture started in Brunze Age. Sincethen, management of water resources is presumed to be the major interest of the ancientpeople and government. Historicalrecords indicate that a number ofhydraulic structures were constructedfor paddy irrigation.

The first earthen dam, Byeokgol-je,with a storage capacity to irrigate pad-dy field over 10,000 hectares area wasconstructed in 330 A.D.. It had anembankment over 3,000 meters longwith five gates. Two gates were oper-ated as spillways and the others asintakes of irrigation water. Some ofthe gates are still remained as shownin Figure 7.1.

Chapter 7

Figure 7.1 Gate pillars of Byeokgol-je

More dams were constructed later, including Nul-je and Hwangdeung-je. Only histori-cal records tell that these two dams were over 1,000 meters long. Meanwhile, some ofdams such as Uirim-ji, are still in use, which is one of the reservoirs constructed during540-575 A.D.. It is quite interesting to see that these dams were constructed in this earlyperiod of time. This effort was continued and resulted in significant increases in crop pro-duction and more efficient irrigation systems in the following era.

7.1.2 Land and water resource development by unified empires (668 -1392 A.D.)

During 600’s, Silla dynasty completed the unification of Korean peninsula, whichresulted in great changes in the society including agriculture. Dynasty owned lands aswas the common practice in most ancient kingdoms. This held true for Goryeo dynastyafter Silla. During these periods, more dams were constructed and some old ones wererepaired 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 againstMongolian threat, farmers were allowed to use the reclaimed land to grow crops, mostlyrice. Goryeo dynasty (918-1392 A.D) strongly encouraged land reclamation for greatercrop production. More dams including Namdae-ji in Hwanghae province and Gonggeom-ji in Sangju were constructed.

Waterwheel for irrigation was also introduced from China during this period. Althoughthey drew interests from farmers and scientists, they were not widely used in the nation.

7.1.3 Systematization of irrigation and drainage (1392 - 1910 A.D.)

With the development of agricultural technology during Joseon dynasty from 1392,large irrigation programs were systemized to help increase crop production. Many refer-ences 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 rectangularshape for efficient irrigation and drainage.

The world’s first rain gauge was invented during this period and installed to collectrainfall data at major stations in each province. During the fifteenth century, dynasty ini-tiated channel improvement for flood control. Channel banks were constructed for riverimprovements, which resulted in a dramatic increase in rice production. The channelimprovement for flood control continued till the end of the dynasty.

Scientists during the period of King Sejong also measured water levels in channels forflood control. For this, devices similar to staff gauge were invented and installed in themajor streams in the capital city. During this period, a primitive pump was developed fortesting. The first field rearrangement was also initiated during this period.

A number of crop-related references were published during this period indicating theimportance of rice cultivation. More advanced water pumps were developed and used inthe 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.

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83

In the seventeenth century, double cropping became possible due to the introduction oftransplant in rice cultivation. Rice cultivation with transplanting requires more irrigationwater 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 loca-tion 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 Jaeryeongriver in Hwanghae province. Since they were constructed near an estuary, more advancedskills were required. The dams provided irrigation water for over 9,000 hectares of ricepaddies. 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 whichhe emphasized the importance of irrigation and drainage, comparing them to the bloodvessel system of human body, and urged for the improvement of irrigation and drainagesystems and related technology. He categorized the technology related to irrigation anddrainage as follows:

1) Appropriate management of drainage and dredging channels2) 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 implementhis idea.

7.1.4 Forced modernization of irrigation and drainage (1910 - 1945 A.D.)

Japan’s influence on the Korean peninsula began during the 1890’s until complete col-onization in 1910. In order to solve her food shortage problem, Japan purchasedreclaimable land in Korea for cropping at low cost, and began to improve irrigation anddrainage conditions. During this period, 520,000 hectares area was developed for cropproduction. Irrigation system was improved over 335,000 hectares area of paddy fieldsand about 53,000 hectares was reclaimed for cultivation. Concrete arch dams were alsoconstructed during this period. In addition, the first and only union (association) for irri-gation was organized in 1908.

Even though the main reason for establishing modern hydraulic and irrigation/drainagesystems by Japan in Korea is her exploitation of food, modernized facilities and technolo-gies were introduced to the Korean agriculture during this period.

7.1.5 Achievement and progress since independence (1945 - )

With the independence from Japan, government continued to drive the movement forself-sufficiency in food. Therefore, greater efforts were made for the new development ofwater resources for irrigation, which resulted in the construction of large-scale damsincluding several estuary dams. Various international loans were granted for large-scale

Progress of Irrigation and Drainage in Korean Paddy Field Chapter 7

84


developments in the agricultural field. Development on groundwater was made for irriga-tion during 1960’s, particularly in areas where surface water is limited. Asan estuary damwas completed at the end of 1973, providing a total storage capacity of 123,000,000 m3.For about 20 years from 1970 to 1980’s, six large estuary dams were constructed. Thetotal capacity of these dams was approximately 751,000,000 m3, providing irrigationwater for over 112,000 hectares. In addition, several large dams were constructed for irri-gation in inland areas during 1970’s. These dams provided irrigation water to about35,000 hectares paddy fields. These efforts resulted in a stable irrigation system coveringabout 76% of paddy fields in the nation.

During 1970’s, government recognized that poor drainage affected rice production insome areas and resulted in frequent flood. Therefore, a program was launched forimproving nationwide drainage systems, resulting in the drainage improvement in over100,000 hectares area and is still in progress.

These efforts made over a long period of time improved irrigation and drainage sys-tems dramatically nationwide such that 10-year drought design period was applied inplanning irrigation systems and self-sufficiency was achieved in rice consumption. Thestable and improved irrigation and drainage system seems to be the main driving force inachieving good harvests in rice for recent consecutive years.

7.1.6 Current issues on irrigation and drainage in Korea

Agricultural environment in Korea has been affected by the rapid changes in bothsocial and industrial structures. Water quantity and quality issues are the major problemsto be solved. Recent report by Population Action International of United Nations advisedon 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 increasingmunicipal and industrial water demands competing with the irrigation use.

In addition, deterioration of water quality is a limiting factor in irrigation use of waterresources. Even though many wastewater treatment facilities have been constructed, theyare located mostly in or near large urban areas. Municipal sewage is discharged withoutappropriate treatment in most rural areas. Thus water quality is seriously deteriorating instreams of rural regions. Particularly, quite a few estuary reservoirs are experiencingrapid deterioration of water quality since they are located downstream. Many of them, infact, are under eutrophication. Crop production is being affected in fields receiving irriga-tion water from the eutrophic reservoirs. Therefore, not only the construction of addition-al treatment facilities, but nutrient management through tertiary treatment and non-pointsource pollution control should be taken into account in planning water quality manage-ment programs.

Another issue is the efficient management of irrigation and drainage systems. Severalfacilities are old and are in need of repairs. Many of them should be replaced or repaired inthe near future. Multiple uses of irrigation water may also be included in the managementissue. A large number of reservoirs in rural area are constructed solely for irrigation pur-pose. For a more efficient use of water resources for the future, the functions of irrigationsystems should also include such uses as water supply for rural communities, among others.

85


Figure 7.2 Average water resources and water use in 1999

7.2 Development of irrigation water

Tai Cheol Kim and Joongdae Choi

It is a common knowledge that irrigation and drainage technologies play key roles inachieving sustainable development of rice culture.

7.2.1 General water resources

Average annual precipitation of 1,274 mm produces 126.7 billion m3 of water, of whichan average of 69.7 billion m3 discharges into rivers and streams at a 55% runoff rate and57 billion m3 evaporates or infiltrates as a direct loss (Figure 7.2). However, as far aswater shortage is concerned, evaluation of water resources based on the average precipi-tation is meaningless. An annual precipitation of 890 mm with 20 year drought frequencyproduces only 88.5 billion m3 of water, of which 35.4 billion m3 discharges into riversand streams showing a 40% runoff rate and 53.1 billion m3 evaporates or infiltrates. All35.4 billion m3 discharged water must be used to meet 37 billion m3 of water demand inthe year 2011. This is the reason why Korea is classified into the country group experi-encing water shortage. Thus, It would be most favorable to construct dams for storingfloodwater in the reservoir.

The water demand in 1999 amounted to 30.1 billion m3, which comprises 6.2 billion m3

for municipal use, 2.6 billion m3 for industrial use, 15.4 billion m3 for agricultural use,and 5.9 billion m3 for in-stream flow augmentation. The water supply during the same

Potential WaterVolume 126.7

billion ㎥

Stream flow69.7

Non-flood23.2

Effective 17.2

Supply 32.5

Flood46.5

Non-effective6.0

Dam supply12.7

Sea 39.8

Potential Ground Water117.0

Domestic 6.2Industry 2.6Agriculture 15.4In-Stream 5.9

Demand 30.1

Ground Water 2.6

Percolation12.6

Evaporation &Infiltration

57.0

Atmoshere55.0

period was 32.5 billion m3 consisting of 17.2 billion m3 of river discharge, 2.6 billion m3

of ground water, and 12.7 billion m3 of stored water in the reservoirs.

River discharge Since two-thirds of river water flows during the three months of floodseason, much of the floodwater ends up in the sea. Thus, on the average, only 23.2 billionm3 out of 69.7 billion m3 of river discharge are available for use. River discharge remainslow 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 toSeptember resulting in serious floods.

Dam and reservoir storage The 35 large dams providing hydro-power, municipal andindustrial water, and flood control have a total water storage capacity of 13.5 billion m3.Another 17 large dams with a total water storage capacity of 3.9 billion m3 are under con-struction. According to long-term plans, 28 multipurpose dams with a total water storagecapacity of 4.3 billion m3 and many agricultural dams with a total storage capacity of 0.8billion m3 will be constructed by 2011. However, water resource development hasbecome more difficult and several reservoir sites planned are caught in disputes due toincreases in construction and compensation costs and strong opposition from the inhabi-tants and environmentalists. Serious nationwide controversy between the developmentand conservation of water resources had been on the table for several years. Finally, thepolicy of water resources was converted from development to conservation, a turningpoint resulting in the cancellation of the proposed Donggang dam (Figure 7.3) for watersupply and flood control.

Ground water A total of 3.4 billion m3 ofground water was withdrawn from 946,000wells in 1999, resulting in a drop in the groundwater table, which in turn is closely related tothe discharge of base flow and the water quali-ty in the streams. The ground water use con-sists of 1.6 billion m3 for domestic, 1.5 billionm3 for agricultural, 200 million m3 for industri-al, and 79 million m3 for other uses, and hasbeen increasing. Approximately 7 billion m3 ofground water are projected to be mined in 2010with 4.2 billion m3 allocated for agriculturaluse.

7.2.2 Present status of rural water develop-ment

In 1999, at the ICID Meeting in Granada,Spain, irrigation, drainage, and flood controlof agricultural lands were declared to be nolonger options. They are necessary for feed-ing billions of people, providing employmentsto the rural inhabitants, and protecting theenvironment. ICID stressed that dams have

86


Figure 7.3 Proposed Donggang dam site canc-elled dueto environmental issues

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 therequirements of society, acceptable side effects, and sustainable environment.

Irrigation development in Korea is represented by the increare of irrigated paddy fieldarea as shown in Table 7.1.

Investment for rural waterdevelopment

Under the policy frameworkof “Comprehensive plan forrural area development” in1989, comprehensive ruraldevelopment projects have beenexecuted for agricultural landand water development, improvement of rural living standards,and off-farm income.A total ofUS$ 22,434 million (24,677billion won) was invested undera comprehensive rural development by 1998. Of this amount,US$ 18,860 million (84%) wasfor agricultural land and waterdevelopment, US$ 2,026 million(9%) for improvement of ruralliving standards, and US$ 1,547million (7%) for off-farmincome projects (Figure 7.4).

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Table 7.1 Paddy field area and irrigated paddy field

YearNationalland area(1,000 ha)

Cultivatedland area(1,000 ha)

Paddyfield area

IrrigatedPaddy field area

%

1970 1,284 745 58.01975 1,277 790 61.91980 1,307 893 68.31985 9,914 2,144 1,325 948 71.51990 9,927 2,109 1,345 987 73.41995 9,927 1,985 1,206 907 75.21996 9,931 1,945 1,176 889 75.61997 9,937 1,924 1,163 882 75.81998 9,941 1,910 1,157 881 76.11999 9,943 1,899 1,153 878 76.2

Figure 7.4 Investment for comprehensive rural development up to 1998

Area (1,000 ha)

Rural water23%

Large scaleproject 11%

Tidelandreclamation

6%

Land and water73%

Agriculturalland and water

84%

Present statusuntil1998

US＄22.4billion

Rural livingstandards

9%Off-farm7%

Disasterprevention

10%Repir5%

Drainage4%

Drought1%

Industrial complex 6%

Industrial complex6%

Farm tourism 1%

Upland consolidation 3%

Farm road pavement 2% Regional infrastructure 0%

Rehabilitation 1%

Paddy consolidation

27%

Rural sewage 0%

Rural settlement6%

Rural settlement6%Advanced village

2%

Advanced village 2%

R&D2%

Drinking 1%

Drinking1%

The concept of rural water development, which originally was focused on the supply ofirrigation water for rice, has now been broaden to include irrigation water for uplandcrops, livestock water, and regional water such as domestic, industrial, and in-streamflow augmentation in rural areas.

Drought occurs frequently during the rice-transplanting season and/or the rice-flower-ing 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 hectaresare now irrigated, while 274,090 hectares or 23.8% of total still rain-fed as of 1999. Only413,000 hectares or 36% of total paddy field areas are secure from droughts occurring at

a 10-year frequency.

A total of 15.4 billion m3 of water foragricultural purpose was withdrawnfrom reservoirs (5.0 billion m3), pump-ing stations (1.8 billion m3), headworks(0.8 billion m3), tube wells (1.4 billionm3), other sources (2.3 billion m3), andeffective rainfall (4.1 billion m3) in1999. Most agricultural water is usedfor rice crop with about 500 million m3

of water applied for upland crops.

Irrigation facilities: reservoir, pump-ing station, weir, and tube well

Major irrigation facilities are reser-voir, pumping station, diversion weir,and tube well (Figures 7.5~7.8). Atotal of 517,100 hectares of paddyfields are irrigated through 18,000reservoirs, 151,700 hectares through6,400 pumping stations, 103,100hectares through 18,320 diversionweirs, 33,100 hectares through 17,130tube wells, 20,200 hectares through3,740 infiltration galleries, and 53,300hectares through other facilities.

ICID concluded in its Granada decla-ration in 1999 that rehabilitation andmodernization must result in additionalbenefits to farmers and be financiallyviable in that operation and maintenancecosts should be at acceptable levels.

88


Figure 7.5 Dae-a dam under re-construction for irrigation, municipal, and small hydro power water

Figure 7.6 Ganggyeong pumping station with weir to supplyirrigation water to 324 hectares of paddy field

The main problems of irrigationfacilities are old age and small size.Fifty five percent of irrigation reser-voirs (Table 7.2) and 31% of pump-ing stations are older than 50 and 20years, respectively. In addition 89%of irr igation reservoirs have aneffective storage capacity of lessthan 1 million m3 (Table 7.3). Thus,irrigation reservoirs have effectivestorage capacity of 3.1 billion m3 andnormal water surface area of 86,664hectares in total. The percentage ofeffective release (actual waterrelease /effective storage capacity) isabout 140%. The benefited areafrom a pumping station is less than25 hectares on an average. Diversionweir has the function to raise the riv-er water level to the desired heightand covers an irrigated area of 6hectares on the average. The abilityof irrigation facilities should bemaintained through rehabilitationworks.

According to the MAF planning,the amount of rural water demand in2011 is expected to be 17.9 billionm3, of which 15.5 billion m3 will beused for agriculture, 0.7 billion m3 forlivestock, and 1.8 bill ion m3 forregional water. The existing facilitiescan only supply 11.2 billion m3, thus,the remaining 6.7 billion m3 should besupplied by new irrigation facilitiesto be built by 2011.

The most critical issue is the construction of new facilities based on with the spirit ofenvironmentally sound and sustainable development. Medium-size multi-purpose damsand reservoirs are advisable due to their many merits. Linked operation of dams in a

89


Figure 7.7 A diversion weir to supply irrigation water to paddy field

Figure 7.8 Drilling of tube well for groundwater abstraction duringdrought period

Year of construction

Number 9,706 3,779 2,475 734 574 312 376

Before1945

1946 ~1966

1967~1971

1972~1976

1977~1981

1982~1986

1987~1999

Table 7.2 Number of irrigation reservoirs with respect to the construction time

90


basin and transfer of water between different watersheds are also some of the preferredmethods though with some limitations. The second issue involves water saving throughefficient water management and reasonable maintenance. The relevant methods of watersaving are rotational or intermittent irrigation with TM/TC system and direct seedinginstead of transplanting.

Repair and reinforcement of irrigation system: modernization, hydro-power generation, raising dam crest, fishway, and irrigation canal.Korea has two distinctive dry and rainy seasons. Seeding and rooting season from early

April to mid June belongs to dry season, during which severe drought and water shortageoccur quite often. The dry season begins from late September, and stream flow duringwinter and spring and reservoir storage are very low. Since many of the agriculturalreservoirs and canals were designed to cope with 10-year recurrence droughts, water sup-ply from these reservoirs often does not meet the water demand even when a shortdrought occurs. Water demand is particularly high during transplanting period from lateApril to late May, when water resources are least available. The large seasonal variationin water demand has forced the development of integrated central water management sys-tems.

These systems are not only built with computers and tele-communication equipments,but runoff measurement and estimation from watershed, accurate reservoir storage mea-surement, short- and long-term storage prediction, water delivery efficiency, real-timemonitoring devices, and equipments for water distribution are also needed. One of theprerequisite for setting up the integrated system is the canal modernization.

In the beginning of irrigation system development, the uppermost priority was put onthe expansion of irrigation facilities such as the construction of reservoirs and canals.These hydraulic structures aged and were damaged with time. Rural water has multi-functions to supply not only irrigation water but also domestic, livestock, industrial, andenvironmental water to the rural area. However, development of new water resources andsupply system are very difficult. Not only is the construction of new dams and canalsvery costly, but land price is also very high and water right complicated. In addition envi-ronmental problems associated with new water resource development may cause seriouscivil disturbances and protests. Therefore, repair and reinforcement of existing irrigationsystems are considered to be the best alternative to meet the increasing water demand.Maximization of water use and supply efficiency through repair and reinforcement ofexisting dams and canals, installation of TM/TC instrumentation systems, networking ofwater resources, and automation of water management have emerged as the major watermanagement policies for large irrigation districts of 300 reservoirs and canals weredesigned to cope with 10-year recurrence droughts, water supply from these reservoirsoften does not meet the water demand even when a short drought occurs. Water demand

Effective storagevolume (106 m3)

Number 15,990 1,572 331 23 16 13 11

Less than0.1

0.1~1 1~5 5~10 10~20 20~50 More than50

Table 7.3 Number of irrigation reservoirs with respect to the effective storage volume

Documents

Achievements and Advanced Technology of Rice Production in ...9-6)61-90.pdf · for cold tolerance was carried out with the construction of cold-tolerance test nursery. Rice varieties