Evaluation of the 'fertigation model', a decision support system for water and nutrient supply for soil grown greenhouse crops

Soil grown greenhouse crops require high fertilisation rates. Combined with the common practice of over-irrigation, leaching of nutrients is a-serious problem. In order to reduce the environmental impact, a 'fertigation' model was developed as a decision support system for irrigation and fertiliser supply. The applicability in growers practice was evaluated during two years on commercial nurseries, growing chrysanthemum (Dendranthema grandiflorum). The evaluation was performed by comparison of the actual water and irrigation strategy of the growers with the strategy recommended by the model in a specific section within the same greenhouse. At one chrysanthemum grower a lysimeter was installed to measure water and nutrient leaching. The model performed well in general, without any yield or quality decline by using the model. The irrigation and the nitrogen surplus were decreased significantly compared to the growers standard and consequently reduced the environmental impact. The results indicate also that application of this model depends highly on the growers' attitude towards the environmental impact of irrigation and fertilisation at one hand and the avoidance of risks at the other.