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Chlorophyll contents and NO3-N concentration in vegetation depend on soil nitrogen availability and crop nitrogen uptake. Crop nitrogen uptake is important as nitrogen is needed for chlorophyll formation. Sap nitrate is more sensitive to changes in N application compared to total N and the leaf petiole sap accumulate nitrates more then other parts of plants. We use this method to reduce sampling time required for precisely determining fertilization and for prevention over fertilization. The objective of this study was to estimate leaf nitrogen and nitrates contents by SPAD meter and Cardy-ion meter and to link observations by comparing optical recording techniques at leaf with laboratory results of total nitrogen and fresh tuber yield. Thus, collected results will directly reflect the nutrient soil supply. Field data are from potato experiment in Bosnia and Herzegovina in 2005, comprising three potato varieties: Liseta, Cleopatra and Adora, receiving similar nitrogen treatments (0, 100, 200 and 300 kg N ha− 1). In four field sampling periods (65, 75, 85 and 95 days after sowing) the SPAD readings were performed and correlated with total nitrogen contents and obtained fresh tuber yield at the end of season. Measurement by Cardy-ion meter are performed on leaf petiole sap and tuber sap of potato and compared with percentage of nitrogen in leaf and tuber. In experiment we found highly significant relationship between SPAD indexes as well and concentration of NO3-N mg-1 with laboratory results of total nitrogen and at the end of the season with tuber yield. Meter readings indicate a significant potato yield responses to N fertilization doses. This result clearly shows more accurate quantification of the nitrogen status of a potato crop by SPAD and Cardy-ion meter, which is important information in potato crop management. |
