Water management in irrigated rice - Rice Knowledge Bank ...

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ContentsPreface1 Rice and water 11.1 Rice environments 11.2 Irrigated lowlands 11.3 The rice field and its water balance 11.4 Groundwater under rice fields 51.5 Rice water productivity 51.6 Global rice water use 71.7 Water scarcity in rice-growing areas 82 The plant-soil-water system 112.1 Water movement in the soil-plant- 11atmosphere continuum2.2 The rice plant and drought 143 Coping with water scarcity 173.1 Land preparation 173.1.1 Field channels 173.1.2 Land leveling 173.1.3 Tillage: reducing soil 17permeability3.1.4 Bund preparation and 18maintenance3.2 Crop establishment 183.3 Crop growth period. 193.3.1 Saturated soil culture 193.3.2 Alternate wetting and 19dryingiv3.3.3 The System of Rice 22Intensification3.4 Aerobic rice 233.4.1 Raised beds 273.4.2 Conservation agriculture 283.5 What option where? 293.6 Sustainability 324 Ecosystem services and 35the environment4.1 Ecosystem services 354.2 Environmental impacts 364.2.1 Ammonia volatilization 364.2.2 Greenhouse gases 364.2.3 Water pollution 364.3 Effects of water scarcity 375 Irrigation systems 395.1 Water flows in irrigation systems 395.2 Field versus irrigation system level 415.3 Integrated approaches 415.4 Irrigation system management 425.5 Irrigation system design 43Appendix: Instrumentation 45A.1 Field water tube 45A.2 Groundwater tube 46References 49iii
PrefaceWorldwide, about 79 million ha of irrigated lowlandsprovide 75% of the total rice production.Lowland rice is traditionally grown in bundedfields that are continuously flooded from cropestablishment to close to harvest. It is estimatedthat irrigated lowland rice receives some 34–43%of the total world’s irrigation water, or 24–30%of the total world’s freshwater withdrawals. Withincreasing water scarcity, the sustainability, foodproduction, and ecosystem services of rice fieldsare threatened. Therefore, there is a need to developand disseminate water management practices thatcan help farmers to cope with water scarcity in irrigatedenvironments.This manual provides an overview of technicalresponse options to water scarcity. It focuses onwhat individual farmers can do at the field level,with a brief discussion on response options at theirrigation system level. The manual is meant as asupport document for training on water managementin rice production. It combines scientificbackground information (with many literature referencesfor further reading) with practical suggestionsfor implementation. The target audience is peopleinvolved in agricultural extension or training withan advanced education in agriculture or watermanagement, who wish to introduce sound watermanagement practices to rice farmers (such as staffof agricultural colleges and universities, scientists,irrigation operators, and extension officers).Introductory chapters analyze the water use andwater balance of rice fields, and water movementin the plant-soil system, and discuss the conceptsof water scarcity and water savings. Consequencesof water scarcity for sustainability, environmentalimpacts, and ecosystem services of irrigated ricefields are discussed at the end. An appendix introducestwo simple instruments to characterize thewater status of rice fields that can help farmers inapplying water-saving technologies.This manual was developed through the WaterWork Group of the Irrigated Rice Research Consortium(which is co-funded by the Swiss Agencyfor Development and Cooperation). The sectionson aerobic rice were co-developed by the CGIARChallenge Program on Water and Food throughthe project “Developing a System of Temperateand Tropical Aerobic Rice in Asia (STAR).” Manypartners from national agricultural research andextension systems in Asia have contributed to thework described in this manual. The manual wasreviewed by Dr. Ian Willet (Australian Centre forInternational Agricultural Research) and Dr. MohsinHafeez (CSIRO Land and Water).The authorsLos Baños, 2007iv
Page 2: Water Management in Irrigated Rice:
Page 8 and 9: Fig. 1.2. Water balance of a lowlan
Page 10 and 11: given in Table 1.1. Water losses by
Page 14 and 15: Distribution (%)1009080706050403020
Page 16 and 17: The plant-soil-water system22.1 Wat
Page 18 and 19: Ψ Air-100 MPaDemandLeafXylemStemRo
Page 20: tive to water deficit than cell enl
Page 23 and 24: Water input (mm)4003503002502001501
Page 25 and 26: Table 3.1b. Yield, water input, and
Page 27: Grain yield (t ha -1 )98A2002 20037
Page 30 and 31: Table 3.5. Water input (I = irrigat
Page 32 and 33: Practical implementationTemperate e
Page 34 and 35: Practical implementationSpecific in
Page 36 and 37: Table 3.8. Comparison of water use
Page 38: Flooded yield (t ha -1 )87A65432102
Page 41 and 42: consumption (Hamilton 2003). Many t
Page 44 and 45: Irrigation systems55.1 Water flows
Page 46 and 47: the main system is supply-driven, f
Page 48 and 49: Table 5.1. Area, water use, and tot
Page 50 and 51: Appendix: InstrumentationDetailed d
Page 52: 0.5 cm in diameter and spaced 2 cm
Page 55 and 56:
Bronson KF, Singh U, Neue HU, Abao
Page 57 and 58:
Lampayan RM, Bouman BAM, De Dios JL
Page 59:
Uphoff N. 2007. Agroecological alte
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