Evaluating irrigation strategies for lettuce by simulation: 1. Water flow simulations

Among crop systems, vegetable crops with high inputs of fertilizer and water represent an important threat to the quality of the water. To give guidelines to growers and decision-makers for crop management, numerous fertilization and irrigation practices in various situations should be evaluated with regard to their production and pollution effects.

Here, we used a model of water flow and solute transport (Lafolie, 1991) to compare three irrigation strategies with regard to their effects on the water balance. The model was run for a lettuce crop for two growing periods (summer and autumn) and over 100 years in French Mediterranean conditions. The three strategies were (1) the current strategy based on the occurrence of rainfall, (2) a strategy based on a simplified modelling of the soil water balance and (3) a strategy based on tensiometer readings.

As expected, strategy 1 was very water and time-consuming. Compared with strategy 2, strategy 3 appeared as a good choice, minimizing the waste of water: it involved less irrigation and less drainage loss. The crop was also less stressed by this strategy.