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The aim was to evaluate the productive performance and nutrient export of maize intercropped with drought-tolerant forage grasses. The experimental design was a randomized blocks in a 2x2x2+1 factorial scheme (two forage grasses species ­ Massai and Buffel; two forage sowing methods - in the furrow and broadcast; and two forage sowing times - anticipated and simultaneous; and monoculture maize as an additional control), with three replicates. The maize+forage intercropping promoted greater competition for resources, especially water, limiting N uptake, chlorophyll synthesis, and biomass production by maize under semiarid conditions. Early sowing gave forage plants a competitive advantage, favoring forage establishment before or immediately after the sowing of maize. Thus, the simultaneous sowing of forage grasses in a semiarid environment is a more appropriate option considering the importance of high levels of chlorophyll to ensure high photosynthetic activity in maize plants and greater capacity of biomass synthesis. Massai intercropped with maize exhibits a greaterpotential for biomass production than Buffel under semiarid conditions. Maize+Buffel result in highest macronutrient export by maize, while maize+Massai result in highest macronutrient exports by total forage biomass under a semiarid environment. The choice of the forage species and its sowing time in relation to maize are the main determinants of successful intercropping systems under semiarid conditions.(AU)

O objetivo foi avaliar o desempenho produtivo e a exportação de nutrientes do consórcio de milho com gramíneas forrageiras tolerantes ao estresse hídrico. O experimento foi delineado em blocos casualizados em esquema fatorial 2x2x2+1 (duas espécies de gramíneas forrageiras ­ Massai e Buffel; dois métodos de semeadura ­ no sulco e a lanço; e duas épocas de semeadura ­ antecipada e simultânea; e monocultivo de milho como um controle adicional), com três repetições. O consórcio milho+forragem promoveu maior competição por recursos, principalmente água, limitando a absorção de N, síntese de clorofila e produção de biomassa pelo milho para condições semiáridas. A semeadura precoce deu vantagem competitiva às plantas forrageiras, favorecendo seu estabelecimento antes ou imediatamente após a semeadura do milho. Assim, a semeadura simultânea de gramíneas forrageiras em ambiente semiárido é uma opção mais adequada, considerando a importância de garantir altos teores de clorofila e, consequentemente, alta atividade fotossintética nas plantas de milho para garantir a capacidade de síntese de biomassa.Massai consorciado com milho apresenta maior potencial para produção de biomassa do que Buffel em condições semiáridas.Milho+Buffel resulta em maior exportação de macronutrientes pelo milho, enquanto milho+Massai resulta em maior exportação de macronutrientes pela biomassa forrageira total em ambiente semiárido.A escolha da espécie forrageira e sua época de semeadura em relação ao milho são os principais determinantes do sucesso do consórcio no semiárido.(AU)

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The aim of this study was to assess the chemical characteristics of a continuous aerobic composting process with passive aeration of feed material from the production and slaughter of small ruminants at different moisture levels. The composting process was performed in a brick barn with solid residues (manure and carcass parts) from the slaughter of goats and sheep along with chopped dry elephant grass and tree trimmings. The treatments employed three moisture contents (30, 50, and 70% water) and four sample collections at timed intervals (0, 30, 60, and 120 days), with three repetitions. The variables evaluated were the chemical attributes of the generated compost. The compositing process increased the concentrations of the elements Ca, Mg, S, Cu, Fe, Mn, and Zn and reduced the pH, lignin, and lignin/nitrogen ratio. The levels of N, P, and B increased up to 111, 61, and 94 days, respectively, whereas no change in the K content occurred. At the end of the process at 120 days, the contents of N, P, Ca, Mg, S, B, Cu, Fe, Mn, Zn, and electrical conductivity were increased by 33.7, 6.3, 17.5, 16.3, 666, 22, 31.3, 49.7, 30.4, 29.4 and 16.1%, respectively. The pH and lignin values decreased by 8.4 and 27.2%, respectively.(AU)

O objetivo deste estudo foi avaliar as características químicas de um processo contínuo de compostagem aeróbia com aeração passiva com material de alimentação proveniente da produção e abate de pequenos ruminantes, realizado com diferentes níveis de umidade. O processo de compostagem foi realizado em celas de tijolos, com resíduos sólidos (esterco e partes de carcaça) do abate de cabras e ovelhas, juntamente com capim-elefante seco picado e aparas de árvores. Os tratamentos empregaram três teores de umidade nas pilhas (30, 50 e 70%) e intervalos de tempo (0, 30, 60 e 120 dias) de avaliação do material compostado, com três repetições. As variáveis avaliadas foram os atributos químicos do composto gerado. O processo de compostagem aumentou as concentrações dos elementos Ca, Mg, S, Cu, Fe, Mn e Zn e reduziu o pH, o teor de lignina e a razão lignina/nitrogênio. O N, P e B apresentaram maior teor com 111, 61 e 94 dias, respectivamente. O K não teve sua concentração alterada. O teor de água de 70% produziu os maiores teores de N e menor razão lignina/N. Ao final do processo de compostagem, em 120 dias, houve aumento dos teores de N, P, Ca, Mg, S, B, Cu, Fe, Mn, Zn e condutividade elétrica em 33,7; 6,3; 17,5; 16,3; 666; 22; 31,3; 49,7; 30,4: 29,4 e 16,1%, respectivamente. E houve decréscimo nos valores de pH e lignina em 8,4 e 27,2%, respectivamente.(AU)

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ABSTRACT The aim of this study was to assess the chemical characteristics of a continuous aerobic composting process with passive aeration of feed material from the production and slaughter of small ruminants at different moisture levels. The composting process was performed in a brick barn with solid residues (manure and carcass parts) from the slaughter of goats and sheep along with chopped dry elephant grass and tree trimmings. The treatments employed three moisture contents (30, 50, and 70% water) and four sample collections at timed intervals (0, 30, 60, and 120 days), with three repetitions. The variables evaluated were the chemical attributes of the generated compost. The compositing process increased the concentrations of the elements Ca, Mg, S, Cu, Fe, Mn, and Zn and reduced the pH, lignin, and lignin/nitrogen ratio. The levels of N, P, and B increased up to 111, 61, and 94 days, respectively, whereas no change in the K content occurred. At the end of the process at 120 days, the contents of N, P, Ca, Mg, S, B, Cu, Fe, Mn, Zn, and electrical conductivity were increased by 33.7, 6.3, 17.5, 16.3, 666, 22, 31.3, 49.7, 30.4, 29.4 and 16.1%, respectively. The pH and lignin values decreased by 8.4 and 27.2%, respectively.

RESUMO O objetivo deste estudo foi avaliar as características químicas de um processo contínuo de compostagem aeróbia com aeração passiva com material de alimentação proveniente da produção e abate de pequenos ruminantes, realizado com diferentes níveis de umidade. O processo de compostagem foi realizado em celas de tijolos, com resíduos sólidos (esterco e partes de carcaça) do abate de cabras e ovelhas, juntamente com capim-elefante seco picado e aparas de árvores. Os tratamentos empregaram três teores de umidade nas pilhas (30, 50 e 70%) e intervalos de tempo (0, 30, 60 e 120 dias) de avaliação do material compostado, com três repetições. As variáveis avaliadas foram os atributos químicos do composto gerado. O processo de compostagem aumentou as concentrações dos elementos Ca, Mg, S, Cu, Fe, Mn e Zn e reduziu o pH, o teor de lignina e a razão lignina/nitrogênio. O N, P e B apresentaram maior teor com 111, 61 e 94 dias, respectivamente. O K não teve sua concentração alterada. O teor de água de 70% produziu os maiores teores de N e menor razão lignina/N. Ao final do processo de compostagem, em 120 dias, houve aumento dos teores de N, P, Ca, Mg, S, B, Cu, Fe, Mn, Zn e condutividade elétrica em 33,7; 6,3; 17,5; 16,3; 666; 22; 31,3; 49,7; 30,4: 29,4 e 16,1%, respectivamente. E houve decréscimo nos valores de pH e lignina em 8,4 e 27,2%, respectivamente.

RESUMO

This study was carried out to obtain the estimates of genetic variance and covariance components related to intra- and interpopulation in the original populations (C0) and in the third cycle (C3) of reciprocal recurrent selection (RRS) which allows breeders to define the best breeding strategy. For that purpose, the half-sib progenies of intrapopulation (P11 and P22) and interpopulation (P12 and P21) from populations 1 and 2 derived from single-cross hybrids in the 0 and 3 cycles of the reciprocal recurrent selection program were used. The intra- and interpopulation progenies were evaluated in a 10 × 10 triple lattice design in two separate locations. The data for unhusked ear weight (ear weight without husk) and plant height were collected. All genetic variance and covariance components were estimated from the expected mean squares. The breakdown of additive variance into intrapopulation and interpopulation additive deviations (σ τ (2)) and the covariance between these and their intrapopulation additive effects (Cov Aτ) found predominance of the dominance effect for unhusked ear weight. Plant height for these components shows that the intrapopulation additive effect explains most of the variation. Estimates for intrapopulation and interpopulation additive genetic variances confirm that populations derived from single-cross hybrids have potential for recurrent selection programs.

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The objective of our study was to characterize and determine the patterns of genetic control in relation to tolerance and efficiency of nitrogen use by means of a complete diallel cross involving contrasting inbred progenies of tropical maize based on a univariate approach within the perspective of a multivariate mixed model. Eleven progenies, previously classified regarding the tolerance and responsiveness to nitrogen, were crossed in a complete diallel cross. Fifty-five hybrids were obtained. The hybrids and the progenies were evaluated at two different nitrogen levels, in two locations. The grain yield was measured as well as its yield components. The heritability values between the higher and lower nitrogen input environment did not differ among themselves. It was observed that the general combining ability values were similar for both approaches univariate and multivariate, when it was analyzed within each location and nitrogen level. The estimate of variance of the specific combining ability was higher than general combining ability estimate and the ratio between them was 0.54. The univariate and multivariate approaches are equivalent in experiments with good precision and high heritability. The nonadditive genetic effects exhibit greater quantities than the additive genetic effects for the genetic control of nitrogen use efficiency.

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Maize crops in Brazil have a wide diversity of management systems. There is a large contingent of family agriculture, which uses little or no agricultural inputs, compared to the rural enterprise which uses the most modern production systems. This difference in the management systems is particularly noticeable in relation to consumption of fertilizers, especially nitrogenous ones. Therefore it is necessary to obtain plants with efficient nitrogen (N) use that also respond to applied nitrogen. Thus, the aim of the study was to evaluate the performance of S0:1 progenies, in top crosses, under two nitrogen levels and select the best ones based on responsiveness and efficiency. Sixty seven S0:1 progenies from populations of single cross hybrids were crossed with two testers (T1 - single cross hybrid; T2 - population per se). A hundred and thirty four hybrid progenies plus ten controls were evaluated in two field trials with different levels of nitrogen (one with average levels - 50 kg ha-1 of N - and the other with low levels of nitrogen - 25 kg ha-1 of N) in a 12 x 12 triple lattice design. It is possible to identify and to select progenies from commercial single cross hybrids that are efficient and responsive to nitrogen application. The non-additive effect was as important as the additive effect for grain yield under different nitrogen levels.

A cultura do milho no Brasil tem uma ampla diversidade no sistema de manejo. Há um grande contingente de agricultura tipicamente familiar que usa pouco insumo agrícola, e também empresas rurais que utilizam o que há de mais moderno em sistema de produção. Essa diferença no sistema de manejo fica bem evidenciada no que refere ao consumo de fertilizantes, especialmente os nitrogenados. Por isso, é necessário obter plantas eficientes no uso de nitrogênio (N) e, ao mesmo tempo, que sejam responsivas ao N aplicado. Desse modo, neste trabalho, objetivou-se avaliar a resposta, a diferentes níveis de N, de progênies S0:1 de milho e sua capacidade de combinação, utilizando dois testadores diferentes. Foram utilizadas 67 progênies S0:1, oriundas de híbridos comerciais, em topcross com dois testadores (T1 - híbrido simples; T2 - população per ser das progênies S0:1). Os top crosses foram avaliados, juntamente com 10 testemunhas, em dois experimentos com diferentes níveis de nitrogênio (nível médio - 50 kg ha-1 de N - e outro com nível baixo - 25 kg ha-1 de N), no delineamento experimental látice triplo 12 x 12. Os resultados obtidos permitiram verificar que não ocorreu alteração no comportamento dos top crosses em diferentes doses de nitrogênio, para produtividade de grãos. É possível identificar e selecionar progênies parcialmente endogâmicas responsivas e eficientes na utilização de N, provenientes de híbridos comerciais. Os efeitos não-aditivos foram tão importantes quanto os efeitos aditivos para produtividade de grão sob diferentes níveis de nitrogênios.