Abstract
Abstract This paper describes the development and calibration of a simple on farm quick test for sap nitrate‐N in potatoes (Solanum tuberosum L). A description is given of the plant tissue to sample, bulk sampling procedures, sap extraction, dilution and measurement of sap nitrate‐N. Thirty petioles of the youngest fully expanded leaves per plot were collected and bulked. Segments 10–20 mm long were excised from near the centre of each petiole, crushed and the sap collected. One mL of this sap was diluted a hundred‐fold. The concentration of nitrate‐N in sap was determined by immersing a test strip into the 1: 100 diluted sap extract and then reading the intensity of colour in the strip by reflectometric analysis with a simple, hand held meter. Three strips were read for each sample tested. Standard solutions were used to calibrate test strips. Linear regression equations were used to investigate the relationships between nitrate‐N concentration determined in sap and dry matter. A highly significant linea...
Published Version
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