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 g ive guidelines to growers and decision-makers for crop management, num erous fertilization and irrigation practices in various situations sho uld be evaluated with regard to their production and pollution effects . Here, we used a model of water flow and solute transport (Lafolie, 1 991) to compare three irrigation strategies with regard to their effec ts 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 Medit erranean conditions. The three strategies were (1) the current strateg y based on the occurrence of rainfall, (2) a strategy based on a simpl ified 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 cho ice, minimizing the waste of water: it involved less irrigation and le ss drainage loss. The crop was also less stressed by this strategy. (C ) 1998 Elsevier Science B.V.