Chlorophyll meter readings, N leaf concentration and their relationship with N use efficiency in oregano

Plant-based diagnostic techniques such as chlorophyll meter (CM) readings and nitrogen (N) leaf concentration are used to determine the level of crop N nutrition, but research is limited on perennial crops and especially on aromatic and medicinal plants such as Greek oregano (Origanum vulgare spp. hirtum). The objectives of this study were to determine in a perennial crop species whether there is a relationship between the CM readings, N leaf concentration, and N use efficiency (NUE) and to use CM readings as a diagnostic tool for predicting dry matter yield in response to N fertilization. The CM readings varied across environments, growth stages, and fertilization treatments and were correlated with NUE. NUE was also affected by the environment, N fertilization, and interactions among these variables. This study provides new information about the effect of N application on CM readings, N leaf concentration, and NUE in a perennial crop such as oregano.