Influence of nitrogen and zinc in the maize (<I>Zea mays</I> L.) crop fenology

Abstract

With the purpose af evaluating the nitrogen and zinc in the maize crop fenology, a field experiment was carried out at Piracicaba, (University of São Paulo, ESALQ), during the agricultural year of2ooo/2001, where a Cargill909 hybrid were used The experimental design was completely randomized blocks with fifteen treatments and three replications, where zinc was applied the ridge at maize sowing day. The treatment had five zinc doses (O, 2, 4, 8 and 16 kg.ha-1), associated or not to the nitrogen, which was applied in three doses (O,120 and 240 kg.ha-1). Ali plots had received, at sowing day ridge, 80 kg.ha-l of P2O5 and 60 kg.ha-1 af K2O. The evaluations were leaf area index, number af fotossintetic active leaves from plant, the height of insert af the ear of corn, stem diameter, first and second internódio stem length and the leaves, stem and pennant dry matters. The results showed that the application of nitrogen in growing doses provided increase in a series of variables. Just the variables leave number and leaf area index at 20 days after the emergency, the first internódio stem and dry matter pennant did not responded to any of the studied nutrients. Doses of N higher than 120 kg.ha-1 did not provide satisfactory increases of the studied variables. High zinc doses (up to 16 kg.ha-l) applied in the sowing did not influenced the studied variables, concluding that, in the work condition, the fitotoxidez risk provide by the excess of this element is minimum.