The objective of this study was to evaluate the effects of stalk/leaf ratio and the stage of maturity on the digestibility of the corn plant. Hybrids AG1051, AG4051, AG5011, DOW2B710, DOW2C577, DOW2A525, NB7315 and P30F90 were used, harvested at the one-half milk line (½ ML), three-quarters milk line (¾ ML) and black layer (BL) stages. A randomized block design was used in an 8 (hybrids) × 3 (stages of maturity) factorial design, with three replications. The means generated were used for grouping into high and low stalk/leaf ratio and a new analysis of variance was generated in a 2 × 3 (two groups and three stages of maturity) factorial design. The whole plant and its stalk, leaf, husk, cob and grain components were incubated in situ in the rumen of three cows for determination of degradability of dry matter and degradable neutral detergent fiber. Stalk/leaf ratio did not influence neutral detergent fiber content or the degradability of dry matter and neutral detergent fiber of any of the components, except for the cob, in which the high ratio group had greater degradable neutral detergent fiber contents. There was a reduction in the degradability of all the parts, except for the stalk and cob, and an increase in the neutral detergent fiber contents of the vegetative parts, except for the stalk. Unlike the vegetative components, the neutral detergent fiber contents of the whole plant decreased throughout the stages evaluated. For degradable neutral detergent fiber, there was a reduction in the whole plant and in its components. The advance of maturity reduces the quality of the vegetative components; however, this loss in the entire plant is moderated by grain filling. Forage quality depends more on the quality of the components than on their proportions in the dry matter.

A calagem é uma prática indispensável para obtenção de altos rendimentos das culturas, em solos tropicais ácidos. Objetivou-se avaliar a nutrição e produção de matéria seca de milho, em solo submetido a calagem estimada por três métodos de cálculo e adubação sulfatada. O experimento foi desenvolvido em casa-de-vegetação, em tubos de PVC, com uma planta por tubo. Utilizou-se Latossolo Vermelho distrófico (LVd), sob vegetação nativa. Foi aplicado calcário dolomítico, tipo filler, nas doses de 4,2 Mg ha-1 6,7 Mg ha-1 e 8,0 Mg ha-1 calculadas pelo método do alumínio trocável, cálcio e magnésio; método da elevação da saturação por bases; e método do tampão SMP, respectivamente, além do tratamento sem aplicação de calcário, combinados com três doses de S (10 mg dm-3 30 mg dm-3e 60 mg dm-3, mais o tratamento sem adição de enxofre. As plantas de milho foram colhidas aos 45 dias após a semeadura, sendo separada a parte aérea do sistema radicular. O método mais eficiente de recomendação de calagem para o milho foi o método da elevação da saturação por bases. A aplicação de doses de enxofre não teve efeito no desenvolvimento do milho, até o estádio avaliado.

Liming is essential for obtaining high yield levels in tropical acid soils. The objective of this study was to evaluate maize nutrition and dry matter yield in soil under liming estimated by three calculation methods and sulfur fertilization. The experiment was carried out under greenhouse conditions, in PVC cylinders, by using one plant per cylinder. Filler dolomite lime was added to an Oxisol collected from native forest, at the 4.2 Mg ha-1 6.7 Mg ha-1 and 8.0 Mg ha-1doses, respectively calculated by the exchangeable aluminum, magnesium, and calcium method; base saturation method; and SMP buffer method, combined with three sulfur doses (10 mg dm-3 30 mg dm-3 and 60 mg dm-3. Control treatments without lime or sulfur were also included. Maize plants were harvested at 45 days after sowing and divided into shoots and roots. The most efficient lime recommendation method for maize was the base saturation method. The application of sulfur doses did not affect the maize development up to the evaluated stage.

Em áreas tropicais há poucas informações disponíveis sobre o efeito da desfolha em milho, principalmente quando ocorre no período do enchimento de grãos. Objetivou-se neste trabalho avaliar os efeitos da remoção do limbo foliar durante o período de enchimento de grãos. Os experimentos foram instalados em 12/11/2005 e 21/12/2005 utilizando-se os híbridos GNZ 2004 e P 30F33. O delineamento experimental utilizado foi o de blocos casualizados com três repetições, em esquema fatorial, sendo duas posições de desfolha (acima e abaixo da espiga), duas porcentagens de desfolha (50% e 100%) e quatro estádios reprodutivos (R1, R2, R3 e R4), mais um tratamento adicional, no qual não foi realizada a retirada das folhas. A remoção do limbo foliar acima da espiga resultou em maiores perdas na produção de grãos em relação à remoção do limbo abaixo da espiga. O efeito da remoção do limbo foliar não variou com os estádios fenológicos considerados. Os efeitos na produtividade de grãos, da remoção do limbo foliar abaixo da espiga foram similares à remoção de 50% do limbo foliar acima da espiga em todos estádios fenológicos considerados. O efeito da remoção do limbo foliar sobre a porcentagem de plantas acamadas e quebradas foi de pequena magnitude.

There is little information, in tropical areas concerning the effects of blade removal on maize crop characteristics. The aim of this research was to evaluate the effects of defoliation during the grain filling period. The experiment was arranged as a factorial complete randomized block design with blade removal at two different plant insertion points (above and below corn ear), with two percentages of blade removal (50% and 100%), and four phenological stages (R1, R2, R3, and R4). There were three blocks. Two identical experiments were installed, in 12/11/2005 and 21/12/2005. The hybrids GNZ 2004 and P 30F33 were evaluated in both experiments. Blade removal treatment above corn ear promoted higher grain yield loss in all reproductive stages in relation to the blade removal below corn ear. Blade removal treatment did not change with phenological stages. Results of blade removal below corn ear were similar to 50% of defoliation treatment above the ear. In addition, corn plant lodging was little affected by manual blade removal.