EVALUATION OF RAPID METHODS FOR NITRATE PLANT SAP ANALYSIS OF GLOBE ARTICHOKE GROWN IN SAND CULTURE

Artichoke has a high nitrogen requirements and often farmers apply excessive amounts of fertiliser that contributes to groundwater pollution by nitrate. Artichoke nitrogen fertilisation can be made more efficient by plant analysis. Petiole sap nitrate concentrations in recently mature leaves was tested as an indicator of crop nitrogen status in artichoke grown in sand culture. Two rapid methods were assessed: a selective ion meter, Cardy Meter^® and a hand-held reflectometer RQflex^®. Artichoke plants were grown in containers filled with sand and subjected to five treatments ranging from deficient to excess nitrogen supply. The five treatments were applied in a randomised block design with four replicates, and with four plants per experimental unit distributed under unheated greenhouse. Nitrate concentration in petiole sap measured by the Cardy Meter^® and the hand-held reflectometer (RQflex^®) was highly correlated with the laboratory method, giving a correlation coefficient (r) of 0.91 and 0.92, respectively. Petiole sap nitrate levels reflected different nitrogen applications rates satisfactorily along the growth cycle. Petiole sap nitrate determined either by the Cardy Meter^® or RQflex^® can be a quick and useful tool to assess artichoke nitrogen status.