Objective: The purpose of this project was to explore the influence of different irrigation water amounts on cotton growth and yield under film mulch drip irrigation basing on Penman-Monteith formula. Method: Basing on Penman-Monteith formula, a plot experiment was carried out according to a certain gradient of the irrigation amount combining with meteorological data and soil moisture to analyze the changing regularity of dry matter accumulation, water consumption, and discuss the relationship among dry matter accumulation, yield and water consumption. Result: Dry matter accumulation of cotton in different growth stages complies with the "S" type changing regularity. The soil moisture content is basically at the suitable condition of water requirement in each cotton growth stage according to the recommend irrigation water amount basing on Penman-Monteith formula, and soil moisture was fully made use of and the goal of water-saving without influencing cotton growth was achieved. The daily average transpiration of cotton presented "low-high-low" tendency in the whole growth stage. The fitting result of dry matter accumulation and water consumption ( R=0.857 8) showed that there was a significant correlation between them. The regression model was established with seed cotton yield ( Y) and irrigation amount ( X): Y=-0.010 8 X2+7.906 9 X-1 029.9 ( R2=0.926 2). Conclusion: The irrigation amount based on the theory of Penman formula basically met the cotton water requirement of each growth stage.
