The absence of nutrient replacement, especially nitrogen (N), is one of the main causes of grazing system underutilization and tropical climate pasture degradation. Therefore, N is a very important nutrient in the pasture maintenance; however, it is necessary to know the maximum limit to be used of this nutrient, since fertilization increases production cost. Thus, the objective of this study was to identify the N dose that provides the highest production of marandu palisadegrass (Brachiaria brizantha cv. Marandu), and the fertilization effect on pasture degradation process and forage nutritive value. Treatments consisted in the application of : 0 (control), 25, 50, 75 and 100 kg N ha −1 cycle −1 of regrowth. The evaluations were carried out during the summers (November to April) of 2015/2016 and 2016/2017. The highest dry matter yield (DMY) and forage accumulation rate (FAR) occurred between doses of 50 and 75 kg ha −1 cycle −1 , with no change in productive potential at higher doses. The reduction in mineral content and the increase in crude protein (CP) are the main changes in the nutritional value of marandu palisadegrass, with no pronounced effect on in vitro dry matter digestibility (IVDMD), indigestible neutral detergent fiber (iNDF) and potentially digestible dry matter proportions of CP in the cell wall (CP CW) and in cellular content (CP CC).The productive effect of nitrogen fertilization under marandu palisadegrass is the increase in DMY and FAR. Thus, the use of nitrogen fertilizers in pasture systems with marandu palisadegrass has a greater impact on the area gain than the individual gain, assuming these systems, the use of nitrogen doses of 50 to 75 kg ha −1 cycle −1 .
Photoreceptors are primarily known as key photomorphogenic modulators of various physiological events during plant development. Although there are different groups of photoreceptors, the phytochrome B (phyB) family mediates developmental responses in a wide range of plant species, from seed germination to flowering. In addition, these molecules also regulate abiotic stress acclimation responses, such as salinity, drought, low/high temperature, high light and heavy metals. The signalling pathways mediated by phyB could enhance plant resistance to environmental stresses, as phyB photoreceptors reduce leaf transpiration, increase the antioxidant system, enhance protective pigments and increase the expression of genes related to plant stress acclimation. Thus, the elucidation of positive or negative roles for phyB in these stress tolerance characteristics would provide essential knowledge for genetic engineering, improving plant growth and development in critical environments. In this review, we cover the main findings on how the phyB family works to modulate abiotic stress by discussing biochemical and molecular aspects of the underlying mechanisms operated by these photoreceptors.
A pot trial in greenhouse conditions was carried out to identify at which defoliation height Mulato II grass (Urochloa hibrida cv. Mulato II) should be managed and to determine whether potassium fertilization is necessary in soil with high potassium content. The experiment was carried out in a greenhouse in a randomized block design with six treatments and five replications. Treatments consisted of a 3 × 2 factorial arrangement, with three defoliation heights (50, 65, and 80 cm) and with or without potassium maintenance fertilization. The production characteristics and chemical composition of the forage plant were evaluated. There was no interaction effect between defoliation height and fertilization with or without potassium on any of the analyzed variables, except for mineral content in Mulato II grass. The tillers and leaves number, shoot dry matter, leaf+sheath, root system, and residue were influenced by defoliation heights and potassium fertilization, except for the leaf blades and root dry matter, leaf blade/ stem+sheath ratio, and leaves number, which were not influenced by potassium fertilization. Higher shoot dry matter was observed at the heights of 65 and 80 cm; however, comparing these two heights, leaf + sheath dry matter was lower at 65 cm. Regarding the grass's chemical composition, there was an increase in neutral and acid detergent fiber and indigestible neutral detergent fiber contents as the defoliation height increased, which resulted in lower production of potentially digestible dry matter, which can compromise the potential use of the forage by animals. Among evaluated treatments, Mulato II grass defoliation is recommended for a maximum height of 65 cm. Potassium fertilization increases the yield and the potentially digestible dry matter content of Mulato II grass, even when cultivated in soil with high potassium content. teor de potássio. O experimento foi realizado em casa de vegetação, em delineamento experimental em blocos casualizados, com seis tratamentos e cinco repetições, em esquema fatorial 3x2. Os tratamentos consistiram em três alturas de desfolha (50, 65 e 80 cm), sendo cada altura de desfolha avaliada com ou sem adubação de manutenção com potássio. Foram avaliadas as características produtivas e a composição bromatológica da forrageira. As alturas de corte e adubação ou não com potássio não apresentaram efeito de interação para nenhuma das variáveis analisadas, exceto para teor de minerais no capim Mulato II. O perfilhamento, massa seca da parte aérea, colmo + bainha, número de folhas e massa seca de raiz e resíduos foram influenciadas pelas alturas de corte e adubação com potássio, com exceção a massa de lâminas foliares, raiz, relação lâmina foliar/colmo+bainha e número de folhas, que não foram influenciadas pela adubação potássica. Observou-se maior massa seca de parte aérea nas alturas de 65 e 80 cm, contudo, comparando estas duas alturas, houve menor massa seca de colmo+bainha na altura de 65 cm. Em relação à composição bromatológica do capim Mulato II, houve inc...
Aimed to evaluate the bromatological composition of different genotypes of elephant grass (Pennisetum purpureum Schum.) to energy production through combustion. The experimental design was a randomized block with 3 repetition and the treatments arranged in a subdivided plots scheme, considering as a plots the thirteen genotypes and harvests (dry and rainy) as subplots. The genotypes evaluated were Cubano Pinda, Porto Rico, Vrukwona, Piracicaba 241, Cuba 116, Taiwan A-25, Mecker, Napier, Canará, Guaçu, Cameroon, CNPGL 93-41-1 and CNPGL 91-25-1 clones. The experiment lasted two consecutive years with harvests made every 6 months, with a harvest in the dry season (September) and another one in the rainy season (March), totaling 4 harvests. For dry matter content analysis, three tillers were selected at random and dried in an oven at 55ºC until reaching a constant mass. For biomass quality analysis, the samples were ground in Willey type mills with 1 mm sieves, submitted to bromatological analysis to determine the neutral detergent fiber, acid detergent fiber, hemicellulose, volatile materials, and fixed carbon content. Higher levels of dry matter (greater than 44.4%), acid detergent fiber (greater than 44.8%), volatile matter (greater than 94.3%) and higher calorific value (greater than 3,450 kcal kg-1) occur in the dry period of the year and in genotypes Mercker, Piracicaba 241, Guaçu and BRS Canará genotypes.
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