The response of the tomato plants to the irrigation regimes compared in the previous study, particularly when compared with the response to the peat fraction in the mixture, was modest, often irregular and subject to complex interactions with the former factor. This result could depend partially on the fact that the parameters for the water regime applied during the trials were chosen to prevent exposing the plants to excessive stress through lack of water or excess water. This note analyses the technique used to apply the water. Two main water application parameters were identified parameter a expressing the mean moisture level of the pot during growing, and parameter b expressing the amplitude of the variation in moisture level between the irrigation threshold and the level to which the water was topped up at each watering. The actual mean volume of irrigation during the cultivation period was compared with the theoretically predicted value and the discrepancy explained. The role of parameter a and b are proposed to define the irrigation regime applied and the water regime as such can be defined by these two parameters a and b, as a general composite index. Furthermore the effect on the biological performance of both parameters a and b were studied obtaining a clearer picture of the effect of the water regime. The role of both parameters, a and b were synthesized in a specific composite index for each individual characteristic of the plant after taking in account the principal causes of their variations.