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-The objective of this work was to estimate the repeatability (r) and the number of samples required to measure the nutritional value of four warm-season forage grasses growing in a semiarid region. The grasses evaluated were Urochloa mosambicensis, Cenchrus ciliaris, Digitaria pentzii, and Megathyrsus maximus. Evaluations occurred under two forage management conditions: stockpiling and grazing. Hand-plucked forage samples were analyzed for dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, and in vitro DM digestibility (IVDMD). Four methods were used to estimate r and the number of samples required: analysis of variance, method of principal components based on the covariance (PCCOV) and the correlation (PCCOR) matrices, and structural analysis (EVCOR). Species were compared by the probability of the difference using the t-test. The method PCCOV presents the highest coefficient of repeatability and, therefore, a lower number of samples required. Lignin is the trait that have the highest number of samples required. In terms of qualitative traits, D. pentzii and M. maximus show the best forage qualities among the species evaluated.Index terms: chemical composition, IVDMD, sampling, warm-season grasses. Predição do valor nutricional de gramíneas na região semiárida por meio da análise de repetibilidadeResumo -O objetivo deste trabalho foi estimar a repetibilidade (r) e o número de amostragens necessárias para mensurar o valor nutricional de quatro gramíneas forrageiras tropicais numa região semiárida. As gramíneas avaliadas foram Urochloa mosambicensis, Cenchrus ciliares, Digitaria pentzii e Megathyrsus maximus. As avaliações ocorreram sob duas condições de manejo da forragem: diferimento e pastejo. Amostras de forragem coletadas por pastejo simulado foram analisadas para matéria seca (MS), proteína bruta (PB), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), lignina e digestibilidade in vitro da MS (DIVMS). Para a análise de r e número de amostragens necessárias, utilizaram-se quatro métodos: análise de variância, componentes principais da matriz de covariância (CPCOV) e de correlação (CPCOR), e análise estrutural (AECOR). As espécies foram comparadas pela probabilidade da diferença, tendo-se utilizado o teste t. Para o método CPCOV, observa-se maior coeficiente de r, portanto, menor número de amostragens necessárias. A lignina é a característica que apresenta o maior número de amostragens necessárias. Em termos qualitativos, D. pentzii e M. maximus mostram melhores características entre as espécies forrageiras avaliadas.Termos para indexação: composição química, DIVMS, amostragem, gramíneas tropicais.

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This study investigated how repeated applications of different types of anaerobic digestates and undigested cattle slurry affected the growth responses and nutritional aspects of ryegrass swards (Lolium perenne L.) and soil nutrient concentrations, in a twoseason field trial. The treatments included four different types of anaerobic digestate, undigested cattle slurry, nitrogen control (Ncontrol) with calcium ammonium nitrate (CAN) and a no fertiliser control, distributed in a randomised block design with three replicates. The different types of biofertilisers drove a comparable average forage daily growth rate varying between 65 and 79 kg ha −1 day −1 (p > 0.05). Crude protein and neutral or acid detergent fibre of the forage were not influenced by any type of biofertiliser (p > 0.05). Most of the anaerobic digestates led to increases in the level of soil available P and K (p < 0.05). Despite the detectable influence of the levels of NPK in the biofertilisers on the plant growth responses, different anaerobic digestates when applied using the same dry matter amounts can drive comparable forage grass growth responses with low influence over the nutritional quality of the ryegrass forage. Repeated applications of anaerobic digestates can help to increase or reduce the losses of the soil available P and K. The application of anaerobic digestate, cattle slurry and calcium ammonium nitrate led to increases in the N content of the soil; however, there were no differences between them, despite their considerable differences in terms of N inputs. This might be linked to the volatility and losses of the readily available N from the biofertilisers applied.

This study investigated whether genotype influences the establishment of Pennisetum purpureum Schumach. The experimental design was a randomized complete blocks with four treatments and eight replications (n=8). The treatments were four genotypes of P. purpureum, two classified as tall sizes: P. purpureum cv. Elephant B and cv. IRI 381; and two as dwarf types: P. purpureum cv. Mott and Taiwan A-146 2.37. They were planted in a tropical wet and dry region of Brazil. Tall genotypes showed superior field sprouting rates (p < 0.05), ranging between 95-99%, while dwarfs varied between 88-90%, however, Elephant B and IRI 381 produced a much lower average number of tillers (31 and 32 linear m-1, respectively), than Taiwan A-146 2.37 and Mott (56 and 41 linear m-1, respectively) (p < 0.05). Dwarf genotypes produced lower biomass yields (p < 0.05), but this was genotype-dependent and did not impact on their establishment. The levels of non-structural carbohydrates (NSC) (>10%) in the planted stems were associated with satisfactory field sprouting of the elephantgrass genotypes. Despite some variations between the genotypes in terms of sprouting, tillering, and growth rates, the kind of genotype had no major significance on the establishment of the elephantgrass.

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