Resumo

MENDOZA-ELOS, Mariano et al. Population density and nitrogen fertilization on chlorophyll, dry matter accumulation and grain yield in normal and QPM maize. Agric. Téc. Méx [online]. 2006, vol.32, n.1, pp.89-99. ISSN 0568-2517.

The objective of this research was to determine the effect of plant stand and nitrogen fertilization on chlorophyll content, dry matter accumulation and grain yield of high quality protein and normal maize. The trial was established in two planting dates, during the spring-summer season of 2003 at Celaya, Guanajuato, Mexico, using a factorial, split-split-plot, experimental design. Cultivars were assigned to large plots, plant stands to medium plots and the small plots were assigned to nitrogen fertilization rates on experimental units of 11.25 m². Chlorophyll content and plant dry matter were sampled four times during the crop cycle. Chlorophyll and dry matter determinations were made by using the chlorophyll meter Spad-502 and dry matter by taking two individual plants from each plot. Grain yield was estimated at harvest maturity. Highest chlorophyll levels in both high quality protein and normal maize were obtained with 100 and 200 kg ha^-1 of N. Plant stands of 70 000 and 80 000 plants/ha showed the highest chlorophyll values at 90 days after planting with 65 and 63 Spad units, respectively. ForN rates, QPM V₂ showed the greatest production of dry matter (237 g/plant) with 100 kg ha^-1 of N. For plant stands this QPM V₂ maize cultivar also produced the greatest amount of dry matter (251.17 g/plant) when planted at 80 000 plants/ha. Average yield of high quality protein maize varieties with 200 and 100 kg ha^-1 of N was 10.2 and 8.8 t ha^-1, respectively, in comparison with 11.8 and 10.9 obtained with V₁ -white seeded normal maize- at the same N rates. The grain yield of high protein quality CMSQ993027 was similar to the best normal seeded check.

Palavras-chave : Zea mays L.; biomass; chlorophyll meter; quality protein maize.

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