PULLMAN, Wash., Sept. 16 (UPI) -- A rapid, less-expensive method for testing nitrate concentration in leafy vegetables did not provide as good results as laboratory tests, U.S. researchers say.
Kristy Ott-Borrelli of Washington State University in Pullman, Wash., said measuring nitrate-nitrogen is necessary because when normal plant growth has been altered, the nitrogen usually used by the plant to form proteins remains in the plant in the form of non-protein nitrogen such as nitrate. Excessive amounts of nitrates can become toxic to those who eat the plants, Ott-Borrelli said.
"It would be advantageous for growers to have rapid and inexpensive methods to accurately measure plant tissue nitrate-nitrogen, allowing them to make fertility and harvest management decisions for these crops," Ott-Borrelli said in a statement.
The study, published in HortTechnology, measured ion selective electrodes and the less expensive and portable ion selective electrode nutrient monitoring devices such as the Cardy nitrate-nitrogen meter.
Ott-Borrelli, Richard Koenig and Carol Miles concluded the extraction and analysis of fresh leaf sap with a Cardy meter was not comparable to procedures in which dry leaf tissue is extracted and analyzed with ion selective electrodes.
Samples for the study were taken from a larger experiment in which 24 varieties of lettuce, Asian greens, and spinach were harvested three times at two locations during winter.