Crop yield response to water - Cra

Lead AuthorTheodore C. Hsiao(University of California,Davis, USA)Contributing AuthorElias Fereres(University of Cordoba andIAS-CSIC, Cordoba, Spain)ACKNOWLEDGMENTSLee K. Heng(Soil and Water Management &Crop Nutrition Section Joint FAO/IAEA Division, Vienna, Austria)Scientists contributingwith experimental dataand tests for thecalibration of AquaCropEdmundo Acevedo(University of Chile,Santiago de Chile, Chile),Jerry M. Benner,Benjamin Zur,L.C. Hammond,James W. Jones(University of Florida,Gainesville, Florida, USA),Jose Cavero(EEAD-CSIC, Zaragoza, Spain),Philippe Debaecke(INRA, Toulouse, France),Steve R. Evett,Terry A. Howell(USDA-ARS, Conservation &Production Research Laboratory,Bushland, Texas, USA),Jose Faci(SIA, Zaragoza, Spain),Lee K. Heng(Soil and Water Management &Crop Nutrition Section Joint FAO/IAEA Division, Vienna, Austria),Gerrit Hoogenboom(University of Georgia,Athens, USA),Immaculada Farré(Department of Agriculture andFood, Perth, Western Australia),Fadi Karam(formerly LARI, Tal Amara, Lebanon;currently ICARDA, Aleppo, Syria),Basilio Rojas-Lara(formerly University of California,Davis, USA; deceased),Pasquale Steduto(FAO, Land and Water Division,Rome, Italy),Patrick Wall(CMMYT, El Batán, Mexico)MaizeGeneral descriptionMaize (Zea mays L.) ranks as the most important crop worldwidein terms of grain production; although wheat and rice are themost important for direct human consumption. Maize seeds areconsumed by humans directly or after processing, and are often the maincomponent of animal feed. Vegetable oil, sugar syrup, alcohol as biofuel,and feedstock for the manufacturing of plastic are commonly derived frommaize seeds. The area devoted to maize and the yield per hectare have beenincreasing over time (Figure 1), total production was 819 million tonne in2009 (FAO, 2011), the last year of available statistics. The grain productionof wheat and paddy rice that year were each about 16 percent less thanthat of maize, with rice planted on about the same of area as maize andwheat planted on 30 percent more than maize. Nearly all the high-yieldingmaize cultivars are hybrids. The increasing use of hybrids in the 1930s ledto a clear acceleration in the yield increase over time. Maize is a C 4 species,which originated in a climate with warm summers. It is grown, however,extensively in temperate regions for grain (Figure 2) as well as for silage.For the latter, the crop is harvested before full maturity, when the grainsare in the late phase of filling and the vegetative material still mostly green,is coarsely chopped and partially fermented as animal feed. Even in areaswith a growing season too short for grain to mature, maize is popular asa crop for silage and forage. The dominant producer of grain maize is theUnited States, with about 41 percent of the world’s total, followed by othertop producing countries China (20 percent), Brazil (6 percent), Mexico,Indonesia and India (2 percent).The crop originated in Central America, where it is traditionally planted inhills. Nonetheless, most of the world’s maize is grown as a row crop and assingle crop. In Mexico and some subtropical countries in Africa and America,maize is frequently grown intercropped with beans. In the corn belt of theUnited States, it is often grown in rotation with soybean. On the northernplain of China, it is commonly grown in rotation with winter wheat. Othercrops grown in rotation with maize include other winter cereals, and severalforage and grain legumes.Growth and DevelopmentMaize germplasm is very diverse (Duncan, 1975), with a wide range of seedsize, plant height, tillering habit, number of leaves per stem, number of114crop yield response to water