RELATIONS BETWEEN THE SPAD INDEX DETERMINED BY CHLROPHYLL METER WITH NITROGEN CONTENT IN LEAVES AND GRAIN YIELD IN MAIZE GENOTYPES

Abstract

The objective of this work was to evaluate the accuracy of the chlorophyll meter readings (SPAD index) for early assessing nitrogen content on maize leaves and to proportionate subsidies for recommending nitrogen fertilization. The assay was carried out with three simple maize hybrids (DKA333B, P32R21 and AG9010) and six forms of nitrogen application during crop cycle, totaling 120 kg ha-1: 100% at sowing stage (S); 40% at S and 60% at 4th leaf stage; 40% at S and 60% at 8th leaf stage; 20% at S and 80% at 4th leaf stage; 20% at S and 80% at 8th leaf stage and 20% at S, 40% at 4th leaf stage and 40% at 8th leaf stage. The experiment was arranged in randomized blocks with four replications in split-plot design, being maize hybrids the plot and portioning of nitrogen fertilization the split. Determinations of the leaf chlorophyll content (SPAD index), evaluated with the chlorophyll meter, leaf nitrogen content, and grain yield were done. The chlorophyll meter readings were efficient to provide early diagnose of nitrogen content at the fourth tally expanded leaf of maize cultivars AG9010 (super-early cycle) and P32R21 (early cycle). Concerning the hybrid DKB333B (normal cycle) there was no correlation between chlorophyll meter reading (SPAD index) and nitrogen content on the fourth fully expanded leaf.

Keywords

• Zea maiz: yield grain
• nitrogen fertilization
• precocious diagnose: leaf analysis