Field diagnostic test for nitrate in tomato petiole sap

Abstract

Four rapid tests for nitrate were assessed for use on tomato sap. The performance characteristics of each were examined. Merckoquant strips were favoured as there was acceptable differentiation and repeatability of response over a suitable working range. Procedures are described for the collection of tomato petiole sap and for the estimation of nitrate in that sap using the rapid test. Sap was diluted 1 :20 with water using plastic ware for the test. A linear relationship was established between nitrate measured by the strip test and by an auto-analyser
method. The linear model was used to successfully predict the nitrate content of further sap collected at Bundaberg, using the strip test. There was no significant difference between operators of the strips nor between batches of strips.