Short Description of the Technology

This technology is commissioned to address the problem of the variable and unpredictable mineral composition of the recycled drainage solution (DS) in closed-loop soilless culture systems (CLS), which poses a serious risk for the nutrition of the crop. To address this problem, an innovative technology has been optimised, validated and demonstrated by the AUA team of ECONUTRI, which is based on the use ion selective electrodes (ISEs) for in-situ daily measurement of the macronutrient concentration in the DS by the grower. To properly utilise the measurements obtained from the ISEs, the team of AUA has developed suitable models based on mass balance equations which are applied through the online operating decision support system (DSS) NUTRISENSE. The NUTRISENSE DSS was designed specifically for managing nutrition in soilless culture systems. The main function of NUTRISENSE in closed-loop soilless cropping systems is the readjustment of the supplied nutrient solution (NS) based on the composition of the DS. If the grower is equipped with an ISE system to measure daily in situ, i.e., in the greenhouse, the macronutrient concentrations in the DS, NUTRISENSE can be used to recalculate in real-time the composition of the supplied NS based on the ISE measurements aiming to optimise the nutrient supply. The output of NUTRISENSE, which comprises the injection rates of single-fertiliser concentrated solutions and target EC and pH values, is automatically transmitted to a multi-tank fertigation system. Such a system  utilizes individual fertiliser stock solutions to implement in real time the new NS composition.

Innovative Features

The mineral composition of the recycled nutrient solution in closed-loop soilless culture systems (CLS) is variable and unpredictable over time and this poses a serious risk for the nutrition of the crop. Currently, this issue is tackled through periodic mineral analysis of DS samples in a chemical laboratory and use of this data to readjust the composition of the supplied nutrient solution (NS) using the measured. However, the results from the laboratory analysis are received by the growers about 3 to 6 days after sample collection and thus the information they provide is not actual anymore. In-situ measuring the mineral composition in the recycled nutrient solution daily by the grower using ISEs, and using the obtained data in real time through a specialised DSS to control the nutrient supply, is an innovative approach that is still hardly applied at commercial level. The ISEs that proved reliable and accurate for use in commercial cropping systems for this purpose are the LAQUAtwin of HORIBA, Japan.

The results in tests and pilot studies conducted by the AUA team showed that the LAQUAtwin ISEs have remarkable accuracy, particularly for the measurement of potassium, calcium, nitrates, and sodium concentrations in the DS samples. The calculation of magnesium levels using EC value and the concentration of the other three cations was also accurate. The strategy implemented through DSS NUTRISENSE proved to be effective in swiftly approaching target concentrations of the nutrient ions NO₃^–, K⁺ and Ca²⁺ in the DS after daily readjustments of the nutrient supply.

Type of Contribution

This technology, by supporting full recycling and no discharge of nutrients and water in greenhouse crops, can prevent emission of nutrients to the aquifers. Thus, this technology addresses the expected impact 2 as stated in the Grant Agreement (balanced N/P flows well within safe ecological boundaries at EU and Associated Countries, regional and local scale, contribute to restoring ecosystems).   

Benefits for farmers, the industry, and the environment

This technology is commercially applicable, offering a novel and effective approach to optimize nutrient management in closed-loop soilless culture systems. The combination of ISEs with the NUTRISENSE DSS and a multi-tank fertigation system provides the means to maintain optimal nutrient concentrations in the RS/DS, thus ensuring optimal crop nutrition and, therefore, it provides confidence for application of closed-loop soilless cropping systems. Consequently, this technology encourages growers to switch over from open soilless cropping systems or even from soil-grown crops to closed-loop soilless systems with full recycling of the nutrient solution. The adoption of CLS prevents the discharge of water and fertilizers to the environment, which constitute about 30% and 40%, respectively, of their total supply. Thus, through the adoption of CLS, the pollution of surface and underground water caused by leaching and run-off of nitrates and phosphorous from greenhouse crops can be significantly reduced.