Résumé
A field study has been carried out in Ismailia Governorate, Egypt, during the seasons 96/97 and 97/98. It aimed to determine nitrogen, status of economically important field crops wheat, maize and sugar beet under field conditions using a portable chlorophyll meter. Readings of the chlorophyll meter were proportional to the chlorophyll density as well as nitrogen concentrations in the plant leaves. Mg concentration of wheat leaves showed a non- significant correlation with the N-Tester readings, while iron concentrations were negatively correlated with the apparatus readings. Both Mg and Fe concentrations in maize leaves were negatively correlated with the meter readings. In contrast, Mg and Fe concentrations in sugar beet leaves showed highly significant positive correlations with the N-Tester readings. Thus, the apparatus can be used to predict N-statiis for the three studied crops. More studies are needed to establish predicting of magnesium and iron using the portable meter under field conditions