Potential effect of climate drought on the yield and water productivity of winter wheat over the Huang-Huai-Hai Plain

Climate change is widely accepted to be one of the most critical problems faced by the Huang－Huai－Hai Plain (3H Plain), which is a region in which there is an over-exploitation of groundwater region and where future warmer and drought conditions might intensify crop water demand. The Huang－Huai－Hai Plain is subject to the middle and lower of the Yellow River basin, the Huaihe River plain, and the Haihe River valley plain, extending over 32°00′–40°30′N and 113°00′E to the east coast. It is surrounded by the south foot of Yanshan Mountain to the north, north foot of Tongbai Mountainand Dabie Mountain and Jianghuai Watershed to the south, and eastern foot of Taihang Mountainand Qinling Range to the west, whereas the eastern boundary lies the Bohai Sea and Yellow Sea. The Huang－Huai－Hai Plain belongs to the extratropical monsoon climatic region.The annual mean precipitation is 500－600 mm (with more than 70% falls in July to September), while the atmospheric evaporative demand is about 800 mm/year. For the wheat－maize rotation system, rainfall can just meet 65% of total agricultural water demand, especially for winter wheat, during which only 25%－40% is satisfied by rainfall. Irrigation water is mainly pumped from groundwater. Drought is one of the most damage and widespread climate extreme facing the world, and has been the relatively restriction factor for agriculture and economy development in China. As world’s largest water consumption industries, irrigation farming system consumes around 70% (even more than 80% for some country) of total freshwater usages. However, the accessible freshwater for agriculture has been challenged and declined along with the booming of population and the increasing water usage in living, industry and environment protection. Additionally, the change of quantitative value and spatial-temporal distribution of solar radiation, heat resources, and precipitation further fluctuate agricultural production. It showed that the precipitation had decreased significantly at the amount of 30mm during past 50 years in North and Northeast China, inducing a rapidly expanding of drought areas. In the background of global warming, the irrigation water resource for agricultural production is expected to be more unstable due to the increasing complexity of the regional difference and the annual/interannual variability of precipitation. Thus, how to produce more food with less water will become a subject to solve urgently in next decades, which in virtually depends on crop water productivity. Thus, improving crop water productivity is of primary importance for alleviate water resources crisis, guarantee national food security, and ensure society sustainable development. Firstly, the main purpose of writing this book is introduced. 3H Plain belongs to semi-arid and semi-humid region. Heat resources can meet the demand of double cropping system. The main cropping pattern is winter wheat-summer maize rotation system. The annual mean precipitation is 500－900 mm with inhomogeneous seasonal distribution that 45%－65% falls in summer.In spring, autumn, and winter, precipitation is insufficient to cover water output. There are about 400 mm of water deficit every year, while almost 150－200 mm was from winter wheat growing season. The winter wheat is typically planted in October and harvested next year in June in 3H Plain. The precipitation of this period is 125－250 mm (25%－29% of the year sums) which can not satisfy the water requirements for winter wheat development, and subsequently induce the high frequency of agricultural drought. Thus, the original intention of publishing this book is to provide reference and technical support for agrometeorological department to enhance disaster prevention and mitigation capacity and ensure national food security through: (1) analyzing the changing characteristics of climatic resources in regional scale, and (2) investigating the potential effect of climate drought on the yield and water productivity of winter wheat over the Huang－Huai－Hai Plain. Secondly, the basic structure and content. This book introduces the basic situation, regional differentiation of agricultural climate resources, meteorological drought characteristics and the evaluation of winter wheat water productivity of 3H Plain. The book is divided into seven chapters. Chapter 1 introduces the basic situation of the studied region, including the geographical location, administrative division, natural environmental condition and agricultural production status. Chapter 2 analysis the characteristics of agroclimatic resources, including the changing characteristics of solar radiation, annual mean temperature, precipitation and potential evapotranspiration. Chapter 3 describes the phenological phase and climatic water deficit of winter wheat, mainly including the impact of climate change on winter wheat phenology and the characteristics of water budget during winter wheat growth period in 1970s and 2000－2015, respectively. Chapter 4 investigates the potential effect of climate drought on winter wheat yield, including the spatial-temporal distribution of arid / humid conditions during winter wheat growing period, characteristics of meteorological drought for different growth stage of typical sites and its potential effect on wheat production. Chapter 5 presents a study on the drought adaptive capacity of wheat with different soil types (cinnamon and moisture soil). Chapter 6 describes the approach to estimate actual evapotranspiration of winter wheat, including the extraction of winter wheat planting information and actual evapotranspirationestimation based on SEBAL model. Chapter 7 evaluates the water productivity of winter wheat, including the research progress, the basic characteristics of wheat production and its rasterization, and the spatial-temporal differentiation of winter wheat water productivity. This book’s composition and publication has taken years of hard work of many experts who conduct long-term research of climatic drought assessment and its potential effect, and gotten a lot of support from Institute of Environment and Sustainable Development in Agriculture (CAAS), Key Laboratory of Dryland Agriculture and Chinese Academy of Meteorological Sciences. We also thank the National Basic ResearchProgram of China (973 Program, 2012CB955904), the National Key Technologies R&D Programs (2012BAD29B01), and theNational Science Foundation for Young Scientists of China (41401510). As a newly introduce book about “Potential effect of climate drought on the yield and water productivity of winter wheat over the Huang－Huai－Hai Plain”, it takes out great effect, and it is inevitable to have made mistakes in this book, so we are expecting scholars and readers to give feedback.