Water and nutrient management and crops response to nutrient solution recycling in soilless growing systems in greenhouses

Water and nutrient management of soilless cropping systems with recycling nutrient solution involves various systems, their management, and decision-making strategies involving models. This chapter presents the essential requirements, system components, the various important variables and mass balance, how these are monitored and controlled as part of irrigation and fertilization. Detailed descriptions are provided for managing ion accumulation and depletion, dissolved organic carbon, ionic nitrogen, as well as strategies for discarding and replenishment of nutrient solutions. Details are provided regarding forms of nitrogen as well as other macro and micro nutrients. Special attention is given to pH management in the root zone particularly with regard to spatial variations and crop response to pH. The effect of climatic variables, such as root zone temperature, are also discussed. Various mathematical models are presented for recirculating soilless culture systems, with specific information about model-based decision support tools for semi-closed and closed systems.