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While corn productivity has been increased by the adoption of high-yield hybrids, there are concerns that increased grain potential may be associated with diminished grain nutrient concentration. Ten corn (Zea mays L.) cultivars representing five technological levels (landrace variety, commercial variety, and double, triple, and single cross-hybrids) were cropped on a Rhodic Ferralsol Eutric soil with high fertility in 2006 (dry year) and 2007 (normal year) in Rolândia County, Brazil. At maturity, grain was evaluated for concentrations of P, K, Ca, Mg, Fe, Mn, Zn, and Cu. In general, differences among cultivars were noted for all nutrients in both years. Concentrations of P, K, Fe, and Mn were lower in the dry year, while Ca, Mg, Cu, and Zn were higher. Soil water availability appeared to exert more influence on grain nutrient concentration than did cultivar development; nutrient removal due to grain harvest was also greatly influenced by rainfall patterns and their impact on corn productivity. Even though genetic differences were noted, which may be useful to breeding programs, long-term testing in subtropical environments will be required to clarify the interaction between genetics and climate events on grain nutrient quality and exportation.

Changes in quantity and quality of corn crop stover can have a large impact on soil conservation and soil carbon (C) sequestration over large areas. The aim of this study was to evaluate changes in production, concentration and amount of C and nitrogen (N) in corn stover fractions due to cultivar development. Two field experiments were conducted in the city of Rolândia (Paraná State, Brazil) using ten cultivars representing five technological levels: single cross hybrids, double or triple hybrids, commercial varieties, and creole cultivars. Plant heights and stalk, leaf, cob, husk and tassel weights were determined at final harvest. Elemental C and N analyses were performed in triplicate for each stover fraction. In general, the creole cultivars had greater height, more dry matter (kg ha -1 ) and C content (kg ha -1 ) in husks, leaves, tassels and stalks, particularly when compared to single cross hybrids or others hybrids. There was a direct relationship between C/N ratio and corn selection for husks in both years and for the others fractions in one study year. This was due to the combined effects of increasing C and decreasing N due to crop selection. Large differences were observed within the same technological levels for the evaluated properties, suggesting a wide variation in genetic background. The quantity and quality of stover fractions vary among cultivars and may affect their use for soil cover, animal feed, biomass energy and other applications.Index terms: C/N ratio; genetic breeding; no-tillage system; integrated crop-livestock systems; renewable energy. RESUMOA alteração na quantidade e qualidade dos resíduos culturais do milho podem impactar a conservação do solo e o sequestro de C no solo para extensas áreas. O objetivo do estudo foi avaliar as alterações na produção, concentração e quantidade de C e N nas frações do resíduo do milho em resposta ao desenvolvimento do cultivar. Foram conduzidos dois experimentos de campo na cidade de Rolândia (estado do Paraná, Brasil), sendo cultivados dez cultivares representantes dos cinco níveis tecnológicos que seguem: híbridos de cruzamento simples, duplo ou triplo, variedades comerciais e cultivares crioulas. No final do ciclo foi determinada a altura das plantas e o peso de colmos, folhas, sabugos, brácteas e pendão. Foi realizada a análise elementar em triplicata para C e N em cada fração do resíduo. Em geral, cultivares crioulas tiveram maior altura de planta e matéria seca (kg ha -1 ) e conteúdo de C (kg ha -1 ) nas brácteas, folhas, pendões e colmo, principalmente em comparação aos híbridos simples ou outros híbridos. Ocorreu relação direta entre a relação C/N e a seleção do milho para brácteas para ambos os experimentos e para outras frações no primeiro experimento. Esse resultado foi devido ao aumento do C e redução do N pela seleção da cultura. Foi observada diferença dentro do mesmo nível tecnológico para as variáveis analisadas, sugerindo ampla variação de linhagem genotípica. A quantidade e a qualidade das frações do resíduo variaram entr...

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