Agricultural and Forest Meteorology, 31 (1984) 1--23 1 Elsevier Science Publishers B.V., Amsterdam --Printed in The Netherlands ACTUAL AND POTENTIAL YIELD FOR RAINFED AND IRRIGATED WHEAT IN CHINA W.H. TERJUNG, H-Y. JI*, J.T. HAYES, P.A. O'ROURKE** and P.E. TODHUNTER University of California, Department of Geography, Los Angeles, CA 90024 (U.S.A.) (Received February 4, 1983; revision accepted September 21, 1983) ABSTRACT Terjung, W.H., Ji, H-Y., Hayes, J.T., O'Rourke, P.A. and Todhunter, P.E., 1984. Actual and potential yield for rainfed and irrigated wheat in China. Agric. For. Meteorol., 31 : 1--23. The parametric water use and crop yield model (YIELD) was applied to China and Korea in order to examine the responses of potential and actual winter wheat yield parameters necessary for optimal crop production in that region. A network of 241 stations provided the seasonal climatic input, consisting of data averaged over approxi- mately a 20 year period. Among the results, highest annual yields under full irrigation occurred in the Yangtze River area, Yunnan--Szechwan--eastern Tibet, Korea and the northeast, and the upper Huang Ho River. Lowest yields were calculated for the north- western interior. High annual yields exceeded 5--6,000 kg ha -1. Under ralnfed-only conditions, the management efficiency of wheat production was higher in many regions than cases with full irrigation. In order to achieve optimum crop yields, about 400 mm of irrigation water was needed in the northwest, contrasted with none required in the south and east of China. A sensitivity analysis was applied to determine the degree of error introduced by faulty, uncertain, or missing environmental input data for the stations utilized in this study. INTRODUCTION Comments have been made to the effect that world food production has reached a turning point in the race with population (Olson, 1982). Also, fears are being expressed that increases in food production will come at increasingly greater costs since potential food production seems to have reached a plateau with the present agricultural technology (e.g., see Wittwer, 1980). Such concerns are exacerbated because of scarcity of water supplies, fluctuating weather, and changing climates. Consequently, it behooves us to begin making regional assessments and inventories of potential and actual yield production for the world's primary food crops. Few systematic treat- ments on a regional scale exist (for a Chinese survey, see Ping-Wei, 1981; for a brief literature survey, see Hayes et al., 1982a, b). This paper is a follow-up * Visiting Scholar, Zhongshan (Sun Yatsen) University, Guangchou (Canton), Peoples' Republic of China. ** Dr. O'Rourke is a Visiting Scholar at UCLA from Litton Systems, Inc., Data Systems Division.