Reducing nutrient imbalance in recirculating drainage solution of stone wool grown tomato

Recirculation of drainage solution reduces the emission of water, nutrients and plant protection products from both substrate-based and water-based growing systems. During cultivation, deviations in nutrient ratios in the root environment may potentially affect yield and quality as well as motivate a grower to discharge the drainage solution. Our objective was to quantify imbalances in nutrient ratios and to assess what part of the nutrient imbalances can be prevented with practical measures. included daily balances for water and individual nutrients, using data from a commercial cherry-tomato grower. The balances showed plant water uptake and uptake of individual nutrients were not strictly correlated. It was also possible to establish individual relations between solar radiation sum and water uptake as well as uptake per individual nutrient. After 200 days of production, an adapted balance was prepared and then used as a model. This model was used to compare various nutrient supply strategies to reduce daily fluctuations in nutrient ratios. Simulations showed the imbalances between supply and uptake could be halved compared with the original grower strategy. This was realized by using a combination of drainage volume percentage, the supply EC and the correlation of the supplied solution EC with solar radiation forecast. The conclusion is that nutrient balances can deliver plant uptake data for water and individual nutrients, which can then be correlated with solar radiation. This can be used to identify and reduce deviations from targeted ratios between nutrients in the supplied solution as well as in the root solution. These conclusions take advantage of information available in practice.