NOTES & UNIQUE PHENOMENA Using a Nitrate Specific Ion Electrode to Determine Stalk Nitrate-Nitrogen Concentration

The end-of-season stalk NO, test has been used to determine N sufficiency in corn (Zea mays L.). Nitrate concentration is commonly determined with flow-injection analysis (FIA), which is accurate but uses hazardous chemicals and is time-consuming. Use of a simpler method of NO, determination, such as the NO, specific ion electrode (SIE), may save time and costs, and reduce hazards. The objective of this study was to compare estimates of stalk NO, concentration by H A and NO, SIE. For FIA, NO, was extracted with 2 M KCI, and the extract was filtered before analysis. For SIE, NO, was extracted with 0.04 M (NH,),SO,, and the extract was analyzed without filtration. The slope of the linear regression between concentrations estimated by SIE and FIA did not differ from 1.0. Use of the NO3 SIE, compared with FIA, reduces costs, sample processing, and use of hazardous