Rainfall in the range of 800 to 1,750 mm, regularly distributed throughout the year, is ideal for passion-fruit. Productivity of around 40 t/ha, has been obtained with a total water supply (rain + irrigation) of 1,300 to 1,470 mm, where 826 mm came from rain. In areas where the rains are insufficient or poorly distributed, irrigation is essential, not only to increase productivity, but also to improve the quality of the fruit, via continuous and uniform production.
Irrigation is needed in areas where the annual rainfall is below 1200 mm per year. Regular watering will keep a vine flowering and fruiting almost continuously. Water requirement is high when fruits are approaching maturity. If the soil is dry, fruits may shrivel and fall prematurely.
The soil water level influences passionfruit flowering. A lack of moisture results in loss of leaves and fruits, especially at the start of their development, and this affects the production and quality of the fruits.
The method most frequently used is localized irrigation, using drip and spray systems. Spraying promotes a greater wetted area of soil compared to dripping, thus permitting greater volume of root system expansion. The drip irrigation system has been more widely adopted by farmers because it provides moisture and aeration conditions that favor the development and productivity of the plants. Drip irrigation has the advantage of not contributing to the formation of a humid transitory microclimate within the culture orchard, thus helps to decrease the risk of diseases.