Severidade de Phaeosphaeria maydis e rendimento de grãos de milho (Zea mays L.) em diferentes ambientes e doses de nitrogênio. / Severity of phaeosphaeria maydis and grain yield of maize (Zea mays L.) in several environments and nitrogen doses.

AUTOR(ES)

Flávio Murilo Pereira da Costa

DATA DE PUBLICAÇÃO

2002

RESUMO

Maize (Zea mays L.) crop management is incorporating the ultimate technological advances in Agriculture, resulting in higher yield. Procedures to reduce diseases severity, as those caused by Phaeosphaeria maydis, are becoming more important. The fungus is a biotic agent that reduces productivity due to plant stress. This is related to disease severity and climatic conditions, mainly air temperature and relative humidity. The research had the emphasis of getting better orientation for management actions, using rational agricultural techniques when susceptible genotypes are used. Under favorable climatic condition for P. maydis, the inadequate crop nutritional management results in higher severity even using tolerant genotypes. Therefore, with the purpose of evaluating five different maize genotypes (four tolerant and one susceptible to P. maydis), the field experiments were carried out in four sowing dates, the first two at "Luiz de Queiroz" campus (Location 1) and the last two at Anhembi Experimental Station (Location 2), both in Piracicaba county, São Paulo State, Brazil, making four environments, all under the influence of five nitrogen doses (0; 60; 120; 180 e 240 kg/ha). According to the results, we concluded: (i) the genotype performance depends on the sowing date, and the nitrogen fertilization increases grain yield only without environmental limitation to plant growth; and (ii) the P. maydis severity depends on the sowing date, nitrogen fertilization dose and genotype susceptibility. The stress caused by high air temperature results in higher severity incidence of P. maydis.

ASSUNTO(S)

maize i nitrogenados time of sowing mancha foliar interaction genotype-environment foliar spot interação genótipo-ambiente milho i fertilizantes nitrogenados fertilizers época de semeadura

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