The ideal indicator of crop nitrogen status should reproduce the relationship of the nitrogen (N) level in the crop and soil system, it must be able to detect deficiency or excess of N and it must be a fast diagnosis to allow correction in the same growing season. The objective of this experiment was to evaluate the efficiency of some plant parameters (nitrogen content and accumulation, leaf chlorophyll content, evaluated by the chlorophyll meter, dry matter and leaf area) as indicators of N level in the maize plant. Five experiments were conducted in the state of Rio Grande do Sul, Brazil, in the 1998/1999 growing season. The reading corresponding to the leaf chlorophyll content was the indicator that most accurately estimated the N level at all stages of development of the maize plant, with the exception of the stage of three to four expanded leaves in one of the experiments. The correction factors utilized for readings of the portable chlorophyll meter (specific weight, dry matter and leaf area) were not efficient in increasing the correlation between readings and grain yield.
Zea mays; chlorophyll; leaf area; dry matter; nitrogen content; measuring instruments
