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A blood meal is a by-product of the meat processing industry and can be used as nitrogen fertilizer due to its minimum content of 10 % Nitrogen. The objective of this work was to evaluate the effect of doses of blood meal, such as nitrogen fertilizer in topdressing, on the production components and the severity of diseases in sweet corn. The experiment was developed at the Federal Institute of Education, Science and Technology of Mato Grosso do Sul (IFMS), Ponta Porã campus, in a Quartzarenic Neosol. The experimental design used was randomized blocks with five treatments of blood meal doses of (0 kg ha-1; 48 kg ha-1; 96 kg ha-1; 120 kg ha-1 and 144 kg ha-1) and one treatment using urea for topdressing fertilization with 120 kg ha -1 of N. The experiment analyzed the severity of white spot on the tasseling and milk grain stages and also the production components: plant height, insertion height of the first ear, stalk diameter, length of the unhusked commercial ears, diameter of unhusked commercial ears, number of grain row, weight of husked commercial ears, weight of unhusked commercial ears and productivity in kg ha-1. The use of blood meal was as efficient as the use of urea as a nitrogen fertilizer for doses starting from 48 kg ha-1, the maximum productivity was obtained when the dose of 112 kg ha-1 of N blood meal was used. The severity of the white spot did not progress in treatments containing nitrogen fertilization in topdressing.

The objectives of this study were to evaluate corn cultivars for efficiency in the absorption and use of nitrogen (N) levels of efficiency through the use of nitrogen in contrasting levels of this nutrient in the greenhouse. The experiment was carried out in a greenhouse and the experimental design was in randomized blocks, with 20 treatments and four replicates, in a 10 x 2 factorial arrangement. All 10 maize cultivars were represented by local varieties and commercial hybrids, and the applied N levels were 100 and 400 mg dm-3. Plots were represented by 8L pots containing 4 plants each, which were harvested in phenological stage V8. The evaluated characteristics were dry matter weight and N level of shoot and roots. The nutritional efficiency of cultivars was also evaluated. The studied cultivars had distinct characteristics concerning N use and absorption efficiency in environments of high and low nitrogen levels. The contrasting N levels allowed the occurrence of differences needed to distinguish the most efficient cultivars. Genotypes efficient for N use and responsive to its application can be selected based on the indexes used in this work. Os objetivos deste trabalho foram avaliar cultivares de milho quanto à eficiência na absorção e uso de nitrogênio (N) através de índices de eficiência de utilização de nitrogênio, em níveis contrastantes desse nutriente em ambiente de casa de vegetação. O experimento foi conduzido em casa de vegetação e o delineamento experimental utilizado foi o de blocos casualizados, com 20 tratamentos e quatro repetições, dispostos em um esquema fatorial de 10 x 2. As 10 cultivares de milho foram representadas por variedades locais e híbridos comerciais e as doses de N aplicadas foram de 100 e 400 mg dm-3. As parcelas foram representadas por vasos de 8 L, os quais continham 4 plantas por vaso, sendo colhidas no estádio fenológico V8. As características avaliadas foram o peso de matéria seca e teor de N da parte aérea e raízes. Também foi avaliada a eficiência nutricional das cultivares. As cultivares estudadas apresentaram características distintas quanto à eficiência no uso e absorção de N nos ambientes com alto e baixo nível de nitrogênio. Os níveis contrastantes de N utilizados permitiram que ocorressem diferenças necessárias para distinguir as cultivares mais eficientes. Genótipos eficientes para uso de N e responsivos a sua aplicação podem ser selecionados pelos índices utilizados nesse trabalho.

Nitrogen (N) is the nutrient that most interferes with maize productivity. The development of cultivarsefficient in N use is an effective strategy to reduce production costs and minimize the dependence on agriculturalinputs. The aim of this work was to evaluate maize cultivars as to their efficiency in absorbing and using N undercontrasting levels of this nutrient. The experiment was conducted in the experimental area of the Federal Universityof Lavras (UFLA), in Lavras, MG, Brazil, in the agricultural year 2006/07. The experimental design was randomizedblocks, with 20 treatments and three replicates, in a 10 x 2 factorial arrangement consisting of 10 cultivars and twoN doses. The characteristics evaluated were grain yield, dry matter weight and N content in grains and shoot. Thenutritional efficiency indices of the cultivars were also evaluated. The maize cultivars presented different behaviorconcerning most of the adopted nutritional efficiency indices. Contrasting nitrogen levels allowed the occurrence ofdifferences among the studied characteristics, which were necessary for the selection of the most efficient cultivars.The hybrids GNZ 2004 and P 30F53 stood out for presenting the best performances for the efficiency parameters used.

ABSTRACT: In the present study, we aimed to assess the in vitro viability of pollen grains from maize cultivars collected at different times and days in the field. Four cultivars (Sol da Manhã, XB 6012, XB 8010, and BRS 2020) were evaluated from the second to fifth day of anthesis in three times. Pollen samples were evaluated for their in vitro viability through standard germination test in liquid and solid media and tetrazolium staining. The experimental design was completely randomized, in 4x4x3 split-split plots with four replicates. Data were subjected to analysis of variance followed by a means clustering test and linear regression analysis. The average percentage of viable pollen varied according to the day, collection time, and cultivar. In general, XB 8010 and BRS 2020 had the highest frequency of viable pollen. The highest percentages of viable pollen were observed on the second day of anthesis at 10:00h.