Nitrate and water uptake rates on a short term basis by a rose soilless crop under greenhouse
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A study of a rose crop in a hydroponic recirculating system, has been carried out to measure the hourly balance of water and nitrate uptake, as a basic information for soilless culture management. Our results suggest different trends in the NO3- uptake pattern, depending on environmental conditions. Effects of global radiation are shown. The close relationship between global radiation and water uptake has already been shown, but nitrate uptake is not so clearly related either to solar radiation or to transpiration. The use of different shading covers during Spring and Summer to avoid the incidence of excessive radiation on the greenhouse, seems to affect the NO3- uptake rate during the day hours. The NO3- uptake rate along the night hours was kept in the range of 0.013 to 0.067 mmol.plant(-1) h(-1), independently of the inside radiation range of the previous day. An oscillatory pattern of NO3- uptake has been observed along the night, with a 3 to 4 hours interval between oscillations.