Chlorophyll relative index for diagnosing nitrogen status in corn hybrids

The aim of the current study was to determine the chlorophyll relative index (CRI) in different leaves and phenological stages of the crop in order to diagnose the status of nitrogen (N) in corn (Zea mays L.) hybrids as a function of N rates applied in bands correlating them with N content in the leaves and crop productivity. The field experiment consisted of two corn hybrids (P30R50 and AG8025) and 6 N rates applied in bands (0, 75, 150, 225, 300 and 375 kg N ha-1), under a factorial 2 × 6 experimental design, arranged in a randomized block with 4 replications. The dose of 295 kg N ha-1 allowed estimating crop yields corresponding to 13.033 kg ha-1. Hybrids and N rates influenced concomitantly CRI in several leaves and phenological stages. The chlorophyllometer is shown to be quite sensitive to nutritional status in corn hybrids as a response to N rates applied in bands since the early stages of the crop growing season for early diagnosis. At the end of the vegetative phase, as well as the reproductive phenological stage the chlorophyllometer performed well as an indicator of efficiency of nitrogen fertilizer application. Key words: Zea mays L., chlorophyllometer, productivity, nitrogen fertilization.