Monitoring of Greenhouse Irrigation Water using Microchip Electrophoresis

Management of water and nutrients must be improved to reduce water quality problems and emission of nutrients to the environment. With microchip capillary electrophoresis (CE) technology, more precise monitoring of the process of irrigation and recirculation is possible in relation to plant needs. A mobile microchip CE platform was developed for performing on-site analysis of greenhouse irrigation water and nutrient solution. Microchip CE offers unique possibilities for fast and automated determination of ions in water. Each measurement produces concentration values of the NH4+, NO3-, K+, Ca-2(+), SO42-, Na+, Mg-2(+), Cl-, HCO3- and H2PO4- ions. With the use of CE technology several measuring sessions were organized in commercial growing farms to study water and nutrient management of crops grown on hydroponics. Samples of drip, slab and drain water at four growing sites, with cucumber and rose crops in autumn climate conditions, were collected on daily and hourly basis during daylight. Variation of the analysis results (expressed as percentage from 24 hour average) during the day can be substantial, with up to 57% for potassium in the root medium. Variation in the slabs was larger than in dripwater, which in turn exceeds drainwater. Variation of individual nutrients was greater than of EC and pH. Variation within a single day was as large as between several days.