Abstract: Temperature stress index, water stress index and dry matter conversion factor are the growth model parameters of crop with drip irrigation under plastic mulch in greenhouse. Taking tomato as experimental material, the factors were determined by minimizing the quadratic sum of the difference between simulated and measured value of the dry matter weight. Taking the maximum economic benefit per unit area as the goal, the economic irrigation system of tomato was analyzed and determined. The soil moisture content before each irrigation in the economic irrigation schedule was taken as the crop's economic irrigation low limit. The results show that the economic irrigation low limit value can be approximated as a constant during the crop growth. The economic irrigation low limit for tomatoes is 0.250, which is 83.9% of the field water capacity, and the coefficient of variation is 0.76%. According to the irrigation low limit for irrigation, compared with the actual irrigation, the irrigation water consumption increased by 6.5%, but the yield and net income increased by 7.8%, it shows obvious effect of increasing production and income.

Key words: greenhouse, drip irrigation under plastic mulch, growth simulation, economic irrigation low limit