Desempenho de híbridos de milho com ciclos contrastantes em função da desfolha e da população de plantas

Abstract

The speed of maize development from emergence to anthesis may affect the response of the crop to important management practices and interfere on the ability of corn to cope with stresses at flowering. This experiment was conducted objecting to evaluate the relationship between earliness and maize response to the increase in plant population and defoliation. The trial was performed in Lages, SC, Brazil, during 1999/ 2000. Three contrasting hybrids in terms of heat unit requirement to reach flowering were tested: P32R21, very early; Premium, early; and C333B, late. These hybrids were submitted to four plant populations: 25,000, 50,000, 75,000 and 100,000 pl ha-1. Genotypes were evaluated with full leaf area and removing half of their green leaves at silking. The plant population required to maximize grain yield was lower for late than for early hybrids. Hybrid P32R21 presented a smaller leaf area and greater grain yield than C333B, regardless of defoliation. This was accomplished due to P32R21 higher capacity to mobilize its stem stored compounds to match the sink demand of the grain.