Since tomato plants are fairly resistant to moderate drought, proper water management is essential to ensure high yield and quality.

The water requirement of outdoor-grown tomatoes varies between 4,000 - 6,000 m³/ha. In greenhouses, up to 10,000 m³/ha of water are required. 70% or more of the root system is in the upper 20cm of the soil. Therefore, a drip system equipped with a fertigation device is advisable.

On light soils or when saline water is used, it is necessary to increase water quantity by 20% - 30%. Water requirements will differ at various growth stages. The need for water increases from germination until the beginning of fruit setting, reaching a peak during fruit development and then decreasing during ripening.

Mild water stress during fruit development and ripening has a positive effect on fruit firmness, taste and shelf-life quality, but may result in a smaller size. Late irrigation, close to harvesting, may impair quality and induce rotting.

Water shortage will lead to reduced growth in general and reduced uptake of calcium in particular. Calcium deficiency causes Blossom End Rot (BER). On the other hand, excessive irrigation will create anaerobic soil conditions and consequently cause root death, delayed flowering and fruit disorders.

Acidic (low pH) irrigation water is undesirable, as it might lead to the dissolution of toxic elements in the soil (e.g. Al3+).