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This experiment was conducted in a greenhouse in Vinces Los Rios (Ecuador). The aim of this work is to evaluate the relationship between different parameters and the nutrient demand of a greenhouse soilless cucumber production system in a tropical climate as well as to propose an empirical model for the design of the nutrient supply to the system. Considering the results obtained in this experiment, there was a high correlation between nutrient demands of the system with nutrient supplies and water uptake but not with leaf area index. With respect to the models, nutrient supplies and leaf area index were the most significant variables for nitrate (NO3−), chloride (Cl−) and manganese (Mn). For calcium (Ca2+), magnesium (Mg2+) and zinc (Zn), nutrients supply was the most significant variable and for the rest of nutrients [phosphates (H2PO4−), sulfates (SO42)−, potassium (K+), sodium (Na+) and iron (Fe)], the three variables assessed were significant. [ABSTRACT FROM AUTHOR]

The aim of this work is to evaluate the relationship between the nutrient concentration in petiole sap and different agronomic and climatic variables for a tomato crop grown in a greenhouse in Mediterranean conditions. In addition, the persistence of the nutrient concentration in petiole sap was investigated with the aim of determining the sampling period that implies the best trade-off nutritional information. The experiment consisted of the selection of 20 sampling points inside the greenhouse. The samples of petiole, fully expanded leaf, and soil solution samples were collected weekly from 86 to 163 days after transplanting. Chloride, NO3−-N, H2PO4−-P, Na+, K+, Ca2+, and Mg2+ concentrations were determined in petiole sap and soil solution obtained by suction cups. Nitrogen, P, K, Cl, and Na concentrations were also determined in leaf. Finally, the petiole sap nutritional diagnosis method is the highest sensitive nutritional diagnosis method which compares soil solution and nutrient leaf content related to yield, and the statistical analysis performed in this research demonstrates that crop evapotranspiration (ETc), vapor pressure deficit (DPV), and leaf area index (LAI) are considered the most significant variables that allow the development of these empirical prediction models regarding nutrient concentration in petiole sap. [ABSTRACT FROM AUTHOR]