Water and nitrate absorption kinetics in the nychthemeral cycle of rose grown in the greenhouse using a recirculating solution

An experimental hydroponic system (nutrient film technique N.F.T. system) was used to measure the water and nitrate uptake rates of rose (Rosa hybrida) on a short term basis: hourly fluctuations over a nychthemera. Nitrate and water uptake are subject to large diurnal variations as is well known for most species. Water absorption closely follows the climatic demand with a large peak occurring during the day, whereas nitrate absorption seems to peak slightly before. Relating absorption to agroclimatic factors, we are able to formulate a model in order to evaluate the nitrate needs of the plant. This approach is a first step in the development of real time algorithms for fertigation computers.