Agricultural Water Management 105 (2012) 32–37 Contents lists available at SciVerse ScienceDirect Agricultural Water Management jo u r n al hom ep age: www.elsevier.com/locate/agwat Determination of evaporation, transpiration and deep percolation of summer corn and winter wheat after irrigation Peng Wang a,b , Xianfang Song b,∗ , Dongmei Han b , Yinhua Zhang b , Bing Zhang b a Key Laboratory of Poyang Lake Wetland and Watershed Research (Jiangxi Normal University), Ministry of Education, Jiangxi, Nanchang 330027, China b Institute of Geographic Science and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China a r t i c l e i n f o Article history: Received 9 July 2011 Accepted 28 December 2011 Available online 21 January 2012 Keywords: Isotope mass balance Evaporation Transpiration Irrigation water use efficiency a b s t r a c t The flux of evaporation, transpiration and deep percolation play an important role in agricultural water management. In this study, oxygen-18 was used to determine the three fluxes in the summer corn and winter wheat field under existing irrigation pattern in Shanxi Province, China. Precipitation, irrigation water, soil water, groundwater and stem water were sampled for oxygen-18 analyses, and supported by hydrological observations. By the method of soil water balance and isotope mass balance, combined with eddy correlation method, the following results are reached. After the irrigation on August 11th, 2008 for summer corn (flowering stage, 90 mm, flood irrigation), transpiration of corn accounts for 71.3% of total evapotranspiration, and the irrigation water use efficiency is 38.0%. And after the irrigation on March 15th, 2009 for winter wheat (re-green stage, 110 mm, sprinkler irrigation), transpiration of winter wheat accounts for 61.7% of evapotranspiration, and the irrigation water use efficiency is 42.3%. Compared to flood irrigation, the deep percolation loss of irrigation water under sprinkler irrigation is lower, especially in the first day after irrigation. Overall, the existing irrigation efficiency is low in study area, and measures should be taken to reduce the deep percolation after irrigation. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Water scarcity is a big problem in China, and the average amount of water per person in China (2300–2400 m 3 /year) is only about one quarter of the world average. Especially in North China, where large population exists, agriculture, industry and municipalities demand more water than available. Agricultural irrigation accounts for 65% of China’s annual water use, which totals 560 billion cubic meters (Li and Peng, 2009). In many areas, groundwater is drawn for irri- gation at rates higher than recharge rates leading to water table decline. Meanwhile, the efficiency of irrigation water use is low. China produces less than 1 kg of grain with 1 m 3 of water, only about half compared to developed countries (Shan and Zhang, 2006). Improving the efficiency of irrigation water is vital for sustainable development of water resources and environment protection in China. The fate of irrigation water in agricultural fields can be summa- rized as: direct evaporation from the soil surface; transpiration of crops; deep percolation below the crop root zone. The amount of water transpired is important, since in essence it is the only water which passes through the crop associated with growth and yield. ∗ Corresponding author. Tel.: +86 10 64889083; fax: +86 10 64889849. E-mail address: songxf@igsnrr.ac.cn (X. Song). Thus, improving water use efficiency becomes an optimization problem where transpiration should be maximized and evapora- tion as well as deep percolation should be minimized. Some methods have been developed to quantify evaporation, transpiration and deep percolation in field studies, such as by using large-scale weighing lysimeter (Liu et al., 2002; Lopez-Urrea et al., 2009), sap flow method (Jara et al., 1998; Trambouze et al., 1998), micro-meteorological methods (Williams et al., 2004; Wolf et al., 2008; Yunusa et al., 2004), remote sensing (Immerzeel et al., 2008; Stehman and Milliken, 2007) and hydrological models (Droogers, 2000; Mo et al., 2005; Tourula and Heikinheimo, 1998). Usually, some methods are combined together to calculate evaporation, transpiration and deep percolation. Those methods are usually costly and time-consuming, and calculations are often complicated by different measuring scales, especially during periods follow- ing precipitation or irrigation events when soil water content and canopy conductance are changing rapidly (Huxman et al., 2004). Stable isotopes of water, 2 H and 18 O have been widely used in studies of water movement in the soil-vegetation-atmosphere con- tinuum. Evaporation, or the loss of water from soil, results in the fractionation of soil water isotopes (Zimmermann et al., 1967). Con- sequently, soil evaporation alters both the soil water content and soil water isotopic composition. In contrast, transpiration, which is the loss of water through stomata and cuticle, does not frac- tionate soil water isotopes at steady state (Bariac et al., 1991). So 0378-3774/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2011.12.024