Disponibilização dos Nutrientes das Fezes de Bovinos em Pastejo para a Forragem Fecal Nutrients Liberation of Grazing Cattle to the Forage

Em local adjacente aos ensaios realizados por Braz et al. (2001) foi estabelecida outra área, com objetivo de avaliar a degradação das placas de fezes depositadas pelos bovinos e a influência dos nutrientes liberados na produção e nos teores de nutrientes da forragem. Foram coletadas 50 placas de fezes imediatamente após a excreção pelo animal e mantidas no campo sob incubação por períodos de 7, 14, 28, 56 e 112 dias. Foi verificada contínua e intensa variação nos teores de potássio das placas, que passaram de 0,25 para 0,05% após os 112 dias; neste período, a liberação do nutriente da placa correspondeu a 90% da quantidade inicial. Os teores de FDA apresentaram, na primeira semana, redução de 50% do inicial, que provavelmente favoreceu a concentração das cinzas na placa, como observado. Não se observou variação dos teores de N e P, sendo que o desaparecimento ocorreu de forma restrita, apresentando a mesma tendência do desaparecimento de matéria seca, provavelmente em função da ação de agentes físicos, já que a atividade biológica nas placas foi baixa. Quanto à influência dos nutrientes liberados da placa na produção e teor de nutrientes da forragem, foram verificadas, após 112 dias de incubação, diferenças quanto à produção e aos teores de K na região central de avaliação, ou seja, num raio de até 25 cm do centro da placa, não foi verificada diferença quanto à produção ou aos teores dos nutrientes em outras regiões avaliadas.<br>In an area adjacent to trials conducted by Braz et al. (2001) another area was fenced to evaluate the degradation of piles feces liberated by the cattle and the influence of nutrients liberated to the forage on the nutrients production and concentrations. Fifty piles feces were collected immediately after excretion by the animal and maintained in the field for periods of 7, 14, 28, 56 and 112 days of incubation. It was observed a continuous and high variation in the potassium contents through feces, that ranged from .25 to .05% after 112 days, in this period, the pile nutrient liberation corresponded to 90% initial amount. ADF contents, in the first week, decreased 50% from the beginning, representing a later tendency for increase in the ADF fecal concentration, as previously observed. As for the concentrations of N and P, it was observed that liberation was restricted and correlated with the degradation of dry matter, probably as a function of low biological activity in the feces and of consequent liberation of these nutrients in the particulate form. Concerning the influence of liberated nutrients through the feces to the forage on the nutrient production and concentration, there was a high variation in K concentration and production only in the central region of evaluation after 112 days of incubation, i.e., in a radium of 25 cm from the pile center, there was no difference in the nutrients production and concentrations in the other evaluated regions

The productivity and response to inorganic fertilisers of species-rich wetland hay meadows on the Somerset moors: the effect of nitrogen, phosphorus and potassium on herbage production

The effects of fertilizer nitrogen (N), phosphorus (P) and potassium (K) on herbage production were investigated in herb-rich hay meadows in Somerset, UK. Swards were cut after 1 July each year, followed by one or two aftermath cuts. Dry-matter (DM) yield at cutting, metabolizable energy (ME) production and recovery of N, P and K were measured over 4 years. Total annual DM production increased from 4.7 t ha-1 without fertilizers to 10.5 t ha-1 with 200 kg N, 75 kg P and 200 kg K ha-1 per year, and ME output from 38.8 GJ ha-1 to 92.5 GJ ha-1. Applying moderate replacement rates of P and K without N increased annual DM and N yields by 43% and 36% respectively, but N response was modest unless high rates of P and K were used. Annual ME output and recovery of N, P and K were all significantly increased by taking an additional, earlier cut for silage, even though DM yield was unaffected. The results suggest that potential output of these meadows is similar to that of a wide range of less diverse permanent pastures. Data from this and a concurrent experiment will help to estimate the financial implications of fertilizer and cutting date restrictions within Sites of Special Scientific Interest and the wider Environmentally Sensitive Areas