Abstract: The effects of water supply on wood production were studied in 1983 and 1984 in a young poplar plantation (Populus deltoides Bartr.cv."Lux" ex.Ⅰ-69/55).The results reveal that the growth of poplar plantation can be greatly promoted by artificial irrigation under the same site condition and cultural measures and the growth increases with the rise of water supply level.In comparison with the control (rainfall only) the.average height of tree increased by 17.2—24.6%,the average D.B.H.increased by 10.7—22.1% and the average volume increased by 22.0—42.6%.The volume increment is caused by the extension of the branches and the expansion of leaf area and crown space under irrigation.In accordance with the cost accounting the economic benifit of irrigation is significant.