Influence of Storage Methods on Total Nitrogen Analysis in Rice Leaves

Crop researchers often store ground plant tissue samples for considerable time before determining their nitrogen (N) concentration. The objective of this study was to determine the effects of storage methods and storage duration on total N analysis in rice leaves. The storage methods investigated were (1) keeping ground leaf tissue in a paper bag, (2) storage in a bottle with additional drying at 70°C for 24 h, or (3) in a bottle without additional drying. Paper bags and sealed bottles were kept under ambient condition. Leaf N concentration was measured about once a month for two years by micro-Kjeldahl method. Storage methods had little effect on leaf N concentration during the two-year storage period. The difference in leaf N concentration was 0.1–0.2 g kg−1 between the samples stored in paper bags and in bottles, which was less than 0.5% of mean value of leaf N concentration. Leaf N concentration was not affected over the two-year storage duration. These results suggest that it is sufficient to keep plant tissue samples in paper bags under ambient condition for at least two years for measurement of leaf N concentration.