The nutrient monitoring project for hydroponic growers, funded by South East Queensland catchments and the Flower Association of Queensland Inc., aimed to gather information to assist growers to fine tune growing practices. Hydroponic flower growers were invited to participate by submitting water samples to a commercial testing laboratory. Growers were asked to provide three samples, including the source water, nutrient solution and waste water at three separate times during the year. Below, we discuss how this information was used to successfully fine tune the nutrient solution. Our case study has been provided by George Wilson, from Wilson Roses in Yeppoon, who grows a variety of roses and gerberas for the local market. The first set of samples highlighted to George that, while the total dissolved salt level, indicated by the electrical conductivity (EC) was in accordance with the agronomist’s recommendations, the balance between the nutrients was not (see recommended balance in figure 1). He then adjusted the balance between nutrients, which was confirmed with the results from the second set of samples. Following this he decided to do his own research by reducing the total dissolved salts to a level where minor symptoms of insufficient nutrition were apparent while still maintaining the recommended balance between individual nutrients. He then defined this as his ‘starvation’ level. By again increasing the total nutritional levels within the same balance he was able to determine the level at which growth and production was optimal. The nutritional levels were confirmed with the final set of analyses.

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