Summary:

The experiment was conducted to evaluate the effect of different irrgation managements during poinsettia cultivation. The existing systems of calculationg evaporative demand and thus irrigation frequency are usually based on growing media moisture sensors or climatic sensors (temperature, relative humidity and solar radiation). Poinsettia ‘Primero Red' was grown in pots (1,2 dm3) in greenhouse and irrigated using drippers, according to three different levels: I - irrigation at 40% ±2, (v/v) of water content in growing medium, II - automatically controlled irrigation according to continuous readings of plant weight (all plants placed on special balance connected with irrigation controller) III - irrigation at 72% ±2, (v/v) of water content. The water content in growng media in each treatments was controlled using capacitance probes ECH2O-10 (Decagon Devices, USA). The obtained results showed that irrigation control system based on continuous readings of specially designed balance connected to the computer gave very good results in poinsettia cultivation. Plant in this treatment had the best plant shape and the highest bract area. Moderate water deficit (irrigation at 40% of water content in growing medium) resulted in significant reduction in transpiration and stomatal conductance and thus reduced plant growth and quality.