Crop yield response to water - Cra

Lead AuthorBas A.M. Bouman(IRRI, Los Baños, Philippines)Contributing AuthorsStephan M. Haefele(IRRI, Los Baños, Philippines),Gabriella Izzi(formerly FAO, Land and WaterDivision, Rome, Italy;currently WB, Washington, USA),Shaobing Peng(IRRI, Los Baños, Philippines),Theodore C. Hsiao(University of California,Davis, USA)AcknowledgmentsEline Vanuytrecht(KU Leuven University,Leuven, Belgium)SCIENTISTS contribUTINGwITH exPERImENTALDATA and tests for theCALIbRATION of AQUACROPStaff of the IRRI, and in particular:Anita Boling,Bas Bouman(Head of the Crop andEnvironmental Sciences Division),Romeo Cabangon,Amnart Chinchest,Syed Jabbar,Shaobing Peng,Rachid Serraj,and Joel Siopongco;Ebrahim Amiri(University of Tehran, Karaj, Iran)Eline Vanuytrecht(KU Leuven University,Leuven, Belgium),Hua Zhong(Wuhan University,Wuhan, China)ZIS(Hubei, China)RiceGeneral descriptionCultivated rice is represented by two main species: (i) Oryza sativa,grown worldwide, with its two ecogeographic races indica, adapted tothe tropics, and japonica, adapted to temperate regions and tropicaluplands; and (ii) Oryza glaberrima, grown in parts of West Africa. In the midnineties,a new rice called NERICA (New Rice for Africa) was developed fromcrosses between O. glaberrima and O. sativa species specifically targeted atthe upland and dryland areas of sub-Sahara Africa (Jones et al. 1997). Twomain rice growing environments are distinguished: lowland (or paddy) rice,where fields have saturated soils with ponded water during crop growth,and upland rice, where fields have well-drained, nonsaturated soils withoutponded water. Rice is grown throughout the year in the tropics, and in thesummer in the subtropics and temperate regions.Rice represents the food of 3 billion people worldwide. The global annualproduction of rough (unmilled) rice is about 650-700 million tonne,of which 90 percent is produced and consumed in Asia (Figure 1). Maincropping countries are China, India, Indonesia, Bangladesh, Viet Nam,Myanmar, Thailand and Philippines (FAO, 2011). Worldwide, there areabout 158 million ha of lowland rice (including double cropping), of which101 million ha are harvested for irrigated rice and provide 75 percent ofthe world’s rice production, while the remaining 57 million ha of rainfedlowland rice contribute 19 percent to the world’s rice production. Some11 million ha of lowland rice area is prone to uncontrolled flooding. Theseinclude deepwater areas, low-lying coastal areas subject to daily tidalsubmergence, and areas affected by flash floods of 1-2 weeks, where theproblem is often excess water but not necessarily prolonged submergence.About 14 million ha of upland rice are usually not equipped with irrigationfacilities, and contribute 6 percent to the world’s rice production. (Figure 2).In most tropical irrigated areas, rice is grown as a monoculture with twocrops per year, while three crops per year occur in places like the MekongDelta in Vietnam. In Pakistan, India, Nepal, Bangladesh, and central China,rice is often grown under irrigation over the summer, in rotation with arange of other crops in winter, including 15-20 million ha of rice-wheatsystems. In China, some 19 of the 30 million ha rice are planted to modernhybrid rice cultivars, which usually outyield the best parent. Rainfedlowland rice is mainly grown in the monsoon season, with large areas inEastern India, northeast Thailand, Laos, and Cambodia. Upland rice was104crop yield response to water