Césio Humberto de Brito

Produtividade e rendimento industrial de híbridos de milho doce em função de espaçamentos e populações de plantas

In the present study we analyzed two sweet corn hybrids, in four row spacing and five plant populations. A randomized block design was used, in a 2x4x5 factorial, corresponding to hybrid (MD2001 and MD2002), row spacing (60; 70; 80 and 90 cm) and plant populations (50; 55; 60; 65 and 70 thousand plants ha-1) with four replications. Aiming to obtain a minimum ear length of 150 mm, recommended row spacing and population were 60 cm and 67 thousand plants ha-1, respectively. Under these management conditions, hybrid MD2001 presented greater ear kernel productivity, while hybrid MD2002 presented better industrial yield. Ear length and diameter, and the number of kernel lines represented the major components in ear and kernel productivity. Kernel depth was the major component for improving the industrial yield.

Resistência ao acamamento de plantas e ao quebramento do colmo em milho tropical

The objective of this work was to evaluate corn genotypes for resistance to lodging and to culm breakage and to describe a new method for evaluating these traits. Assays were carried out in randomized blocks, with 85 tropical genotypes of corn and four replicates in five localities. The force required to pull out the plant and to break the culm and the breaking angle of momentum were evaluated. The measurements were made with equipment developed specifically for this purpose. Variance analyses and the Scott‑Knott test were carried out for the traits. The forces required to pull out the plant and break the culm, and the breaking angle for the culms were significantly interactive with the locality. The means varied from 49.43 to 76.03 kgf for the force required to pull out the plants, from 1.07 to 2.76 kgf for the force required to break the culm, and from 16.15 to 41.18o for the angle at the breakage of the culm. There is genetic variability for selection for resistance to lodging and culm breakage in tropical corn. The method described is efficient for evaluating and differentiating the genotypes.

Inoculation of maize with Azospirillum brasilense in the seed furrow

Several studies addressing the inoculation of cereals with diazotrophic microorganisms can be found in the literature. However, in many experiments, investigators have overlooked the feasibility of applying these microorganisms to the furrow together with the seed, and the effect of bacterial concentration on phytostimulation. The aim of this work was to evaluate the effect of doses of an inoculant based on Azospirillum brasilense, applied to the seed furrow when planting maize, combined with different doses of nitrogen fertiliser. The experiment was carried out in the field, in soil of the cerrado region of Brazil. An experimental design of randomised blocks in bands was adopted, comprising nitrogen (40, 100, 200 and 300 kg ha-1) and doses of an A. brasilense-based liquid inoculant applied to the seed furrow (0, 100, 200, 300 and 400 mL ha-1). The dose of 200 mL ha-1Azospirillum was noteworthy for grain production. This is the first report of the effective application of Azospirillum in the seed furrow when planting maize in the cerrado region of Brazil.

Aspectos morfofisiológicos de plantas de milho e bioquímico do solo em resposta à adubação nitrogenada e à inoculação com Azospirillum brasilense

Nitrogen (N) is a macronutrient that positively affects grain yields in maize crops, being its appropriate management indispensable for a sustainable agriculture, including the use of alternative resources such as diazotrophic bacteria. The aims of this work were to evaluate morphophysiological aspects of maize plants and activity of soil enzymes (urease and fosfatase) due to mineral N fertilization and Azospirillum brasilense inoculation. Two trials were conducted under greenhouse conditions with cerrado soil. A randomized block design was set up with treatments distributed as a 3 x 3 factorial. The first factor corresponded to N rates (0; 100 and 200 kg ha-1) and the second factor to an A. brasilense inoculant (0; 100 and 200 mL ha-1). At the end of this experiment, another trial was done to determine the possible residual effect of inoculation and nitrogen fertilization. Nitrogen application promoted maize plants growth, and increased chlorophyll and nutrient contents. Intensified activity of rhizosphere enzymes related to ammonium and inorganic phosphorus availability was also observed. In addition, N fertilization had residual effect on plant development in the test evaluating the residual effect of the fertilizer. The combination of 200 mL ha-1 of A. brasilense with 200 kg ha-1 of N increased the physiological response of the maize crop.

Quantificação da área foliar e efeito da desfolha em componentes de produção de milho

Corn plant physiological activities and consequently grain yield are affected by reduction in leaf area. The aim of this study was to quantify leaf area in corn plants and evaluate the consequences of different levels of defoliation in crop components. The experiment was conducted in Uberlândia, Minas Gerais state, during the crop year of 2007/2008. The experimental design was in randomized blocks with five replications. The treatments were as follows: control without defoliation; two apical leaves removed; four apical leaves removed; all leaves above spike removed; four intermediate leaves removed; all leaves below spike removed; and all plant leaves removed. The genotype used was hybrid NB7376. To quantify leaf area, images of corn leaves were analyzed using the program QUANT 1.0. The average hybrid leaf area was 5,687.72cm2 per plant, with a leaf area index of 4.4. When all leaves above the spike were removed, grain yields fell by 20% and the mass of 1000 grains decreased by 8%. However, the percentage of damaged grains, the number of grains, and the number of rows per spike, the stand and plant lodging were not altered. The percentage of damaged grains and plant lodging were only affected in total defoliation. All leaf areas in corn are involved in the production of photoassimilates. However, physiologically active leaf area above the spike is characterized as the most efficient in grain yield.

Inoculation of maize withAzospirillum brasilensein the seed furrow

Several studies addressing the inoculation of cereals with diazotrophic microorganisms can be found in the literature. However, in many experiments, investigators have overlooked the feasibility of applying these microorganisms to the furrow together with the seed, and the effect of bacterial concentration on phytostimulation. The aim of this work was to evaluate the effect of doses of an inoculant based on Azospirillum brasilense, applied to the seed furrow when planting maize, combined with different doses of nitrogen fertiliser. The experiment was carried out in the field, in soil of the cerrado region of Brazil. An experimental design of randomised blocks in bands was adopted, comprising nitrogen (40, 100, 200 and 300 kg ha-1) and doses of an A. brasilense-based liquid inoculant applied to the seed furrow (0, 100, 200, 300 and 400 mL ha-1). The dose of 200 mL ha-1Azospirillum was noteworthy for grain production. This is the first report of the effective application of Azospirillum in the seed furrow when planting maize in the cerrado region of Brazil.

Yield of maize hybrids: Is there any association among nitrogen rate, Azospirillum inoculation and fungicide treatment?

Optimization of land use can be attained by incorporating technologies to crop production, such as the use of diazotrophic bacteria, fertilizers, and pesticides. Seed inoculation with Azospirillum is an alternative that favors the incorporation of green agriculture in regions of conventional farming, such as the Brazilian savannah (Cerrado). However, limited information is available about this bacterium’s contribution to agriculture when other technologies are also incorporated. This study evaluated the performance of maize hybrids inoculated, or not, with Azospirillum brasilense, with or without fungicide applications, and subjected to different nitrogen rates under Cerrado field conditions. Each factor analyzed contributes to the increased maize grain yield. The use of inoculants containing plant growth promoting bacteria is a good option to ensure high yield of maize. Still, nitrogen should not be replaced, neither totally nor partially, by seed inoculation with Azospirillum. Fungicide applications should be done, as required, during maize cycle. Moreover, specific maize breeding programs should consider the affinity between Azospirillum strains and maize hybrids, mainly for regions with nitrogen deficient soils, like Cerrado. Thus, by incorporating additional technologies, maize crop farmers can optimize land use and, consequently, reduce the expansion into new agricultural areas. Key words: Foliar protection, nitrogen use, plant growth promoting bacteria, sustainability, Zea mays L.

Redução da área foliar em plantas de milho na fase reprodutiva

A reducao da area foliar em plantas de milho na fase reprodutiva altera a atividade fisiologica e, consequentemente, o acumulo de materia seca nos graos. O objetivo deste trabalho foi estudar a alteracao em caracteristicas agronomicas, provocadas pela desfolha, em plantas de milho, na fase reprodutiva. O experimento foi instalado em Uberlândia, Minas Gerais, no ano agricola de 2007/2008. O delineamento experimental foi de blocos casualizados, com sete tratamentos - testemunha sem desfolha, remocao de duas folhas apicais, remocao de quatro folhas apicais, remocao de todas as folhas acima da espiga, remocao de quatro folhas intermediarias, remocao de todas as folhas abaixo da espiga e remocao de todas as folhas da planta - com cinco repeticoes. O genotipo utilizado foi o hibrido NB 7376. A desfolha foi realizada quando as plantas encontravam-se no estadio R2. Os caracteres avaliados foram: produtividade, densidade de espigas e sabugos, resistencia de raizes e integridade do colmo. Quando foram retiradas todas as folhas acima da espiga, foi observada a perda de 20% na produtividade, foram afetadas a densidade dos sabugos, a integridade do colmo e a resistencia das raizes ao arranquio. A densidade das espigas so foi afetada quando foram retiradas todas as folhas da planta. A extensao foliar que permanece fisiologicamente ativa acima da espiga em milho e a mais eficiente na produtividade de graos.