Feed-Forward control of water and nutrient supply in greenhouse horticulture: development of a system

Minimisation of nutrient and water loss to the environment, prediction and planning of production and product quality, such that they meet the demands of customers, and increased financial return are some of the goals of current greenhouse horticulture. This requires an integrated system for monitoring and control of the nutrient solution, plant growth and product quality. This paper describes the components of such a system. Tomato was selected as example crop. Plant sensors for photosynthesis, radiation interception and fresh growth rate were developed and tested, and the combined plant-substrate model was validated against greenhouse experiments and commercial growth data. Techniques for auto-calibration of the crop model with sensor information were developed. Scenarios describing various fertigation regimes were defined, and a technique for the generation of set points for water and nutrient application on the basis of pre-defined optimisation goals was developed. These goals included drainage volume and nutrient concentration, nutrient application rate, fruit dry matter concentration, and fruit growth rate. The overall system was evaluated in a greenhouse experiment. In comparison with simulated ‘normal’ cultivation, optimisation of water and nutrient application indeed resulted in reduced application and drainage rates, increased fruit growth rate, and a dry matter concentration that met the optimisation goal. In conclusion, the monitoring and control system offers good prospects for efficient control of water and nutrient use, and control of crop growth in future control of greenhouse cropping systems