Relações biométricas entre o estádio de maturação e a produtividade de híbridos de milho para produção de silagem

This experiment evaluated the plant and stem dry matter (DM) content, plant, stem and grain DM productivity of corn cultivars harvested in different maturity stages. A randomized block design, with a 8 × 6 × 2 factorial scheme, composed of eight harvesting times, six corn cultivars and two evaluation harvests (2001/2002 and 2002/2003) was used. Cultivars CO 32, AG 5011, P 3041, DKB 333B, AG 1051 and Z 8550 were harvested when reaching 50% of male flowering, 15 days after this date and later, every week, totalizing eight harvesting times. Cultivar CO 32 showed the highest plant and stem DM content, and the lowest stem DM production, while cultivar P 3041 achieved the lowest plant and stem DM content. The maturity advance resulted in increased plant DM content, (from 14.5 to 46%), stem DM content (from 16.9 to 28%), plant DM production (from 9.6 to 20.9 t DM/ha) and grain production (from 0 to 9.3 t DM/ha). In the 2001/2002 harvest, the production was initially reduced and then increased, while in the 2002/2003 harvest, the production increased up to the 6 ^th harvest and then reduced again. The plant DM content showed low correlations with plant DM production (r ² = 0.27), stem DM production (r ² = 0.13) and grain production (r ² = 0.40). The plant DM production showed high positive correlation with stem production (r ² = 0.83) and grain production (r ² = 0.72). The individual evaluation of the ideal plant harvesting time for a good silage production is fundamental, once the harvesting window for ensilage can be reduced in function of specific characteristics of each material.