Abstract
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.
Highlights
The method of petiole sap analysis is used for the determination of crop nutritional status since1920 [1,2] and is carried out on fresh material, giving a semiquantitative evaluation of the extractable nutrients that are present in soluble inorganic forms in the plant just at the sampling moment [3].Xylem and phloem sap plus apoplastic solution are used to determine the nutrient concentration in a crop [4], but in order to establish a crop a nutritional diagnostic is required for comparison with the sufficiency ranges of this crop [5]
The method of petiole sap shows the best coefficient of correlation with the yield, compared with the different diagnostic methods established: soil solution and leaf nutrient concentrations; nutrient sap concentration can be recommended as the most sensitive nutritional diagnosis methods related to the expected yield
A model is proposed to determine the nutrient concentrations in petiole sap in response to climatic parameters, nutrients in soil solution, and growth
Summary
The method of petiole sap analysis is used for the determination of crop nutritional status since1920 [1,2] and is carried out on fresh material, giving a semiquantitative evaluation of the extractable nutrients that are present in soluble inorganic forms in the plant just at the sampling moment [3].Xylem and phloem sap plus apoplastic solution are used to determine the nutrient concentration in a crop [4], but in order to establish a crop a nutritional diagnostic is required for comparison with the sufficiency ranges of this crop [5]. There are several factors which can modify the nutrient sap concentration, such as fertilizer application, light intensity, phenological stage, and sampling position [2,7,8,9]. Ikeda [10] reported a significant decrease in sap concentration of NO3 − , H2 PO4 − , Ca2+ , and Mg2+ in tomato grown in nutrient solution after 10 days without nutrient solution. Cadahía [12] found a significant variation in the concentration of Cl− , NO3 − -N, H2 PO4 − -P, SO4 2− -S, Na+ , K+ , Ca2+ , and Mg2+ in sap throughout the different phenological stages of a tomato crop. Llanderal et al [14] reported that the selection of sampled leaves (fully grown young leaves, mature leaves, and older leaves) did not modify the Ca2+ , Cl− , SO4 2— S, and Na+ concentrations, whereas NO3 − -N, K+ , Mg2+ , and H2 PO4 − -P concentrations showed great variability due to the selection of the sample leaf, it is necessary to be careful with the sample selection
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