Jozivaldo Prudêncio Gomes de Morais

Sward structural characteristics and herbage accumulation of Panicum maximum cv. Mombaça subjected to rotational stocking managements

Grazing strategies promote changes in sward structure that can affect patterns of herbage accumulation and sward flexibility to management. This experiment evaluated sward structural characteristics and herbage accumulation of Mombaca guinea grass (Panicum maximum Jacq. cv. Mombaca) subjected to rotational stocking managements. Treatments involved grazing when swards reached either 95 or 100% interception of the incident light (LI), to post-grazing heights of 30 and 50 cm, and were allocated to 2,000 m2 paddocks according to a randomised complete block design in a 2 × 2 factorial arrangement with four replications, from January 2001 to February 2002. Sward canopy changed from a vertical to a more horizontal orientation as the light interception area index and height increased from post to pre-grazing. Leaf canopy height pre-grazing was stable throughout the year and around 90 and 115 cm for the 95% and 100% LI treatments respectively, indicating a potential for development and use of target-based grazing management practices. Herbage mass pre and post-grazing was lower for the 95% than the 100% LI treatments, but with higher proportion of leaf and lower proportions of stem and dead material. Treatment effects on herbage accumulation were cumulative and became more evident as the experiment progressed, with up to 6 t ha-1 DM advantage to the 95/30 treatment. Although based on a single year experiment, grazing management should aim for low herbage mass during the transition period from winter to spring in order to allow fast recovery of swards and favour herbage accumulation during the following growing season.

Avaliação do sistema de monitoramento computadorizado de digestão in vitro: 3. Desaparecimento da matéria seca e/ou FDN pela produção de gás

ABSTRACT - The objective of this work was to evaluate the computerised monitoring of the in vitro gas production system andto compare with in vivo and in situ methods. In the degradation methods, corn silage samples with high/low dry matter (DM) contents,with/without inoculate, were used. Evaluating the silage degradation, by the gas production on the fermentation, the results of theextension of degradation (A+D) were 21.5; 22.6; 22.1 and 20.9 mL of gas/100 mg DM, without significant difference. The coeffici entsfor determination obtained on the total gas production in relation to the potential degradation obtained in situ showed to be high forinoculated corn silage with high DM (R 2 = 0.99), non-inoculated corn silage high DM (R 2 = 0.98), inoculated corn silage with low DM(R 2 = 0.94) and non-inoculated corn silage with low DM (R 2 = 0.93). The DM and/or neutral detergent fiber (NDF) disappearance,determined by gas production in the in vitro/gas system, presented similar results when comparing the others evaluated methods.Key Words: corn silage, gas production, in vitro digestion

Ammonia Volatilization from Exposed Soil and Tanzania Grass Pasture Fertilized with Urea and Zeolite Mixture

The aim of this study was to evaluate the effects of a zeolite and urea mixture on ammonia volatilization. Two experiments were carried out: a greenhouse pot experiment and a field trial with Tanzania grass pasture. The pot experiment used five zeolite ratios (0, 12.5, 25, 50, and 100 percent relative to the N-urea level used) mixed with 100 kg ha−1 of nitrogen (N). The field trial used four treatments: 0, 12.5, 25, and 50 percent of zeolite, at the dose of 50 kg ha−1. In the greenhouse experiment, the smallest losses by volatilization occurred at the proportions of 25 percent and 100 percent. During the summer, the mixture of 25 percent of zeolite in N-urea led to a reduction in ammonia volatilization from 33.5 to 7.6 kg ha−1. However, in the winter, volatilization was very low, and there were no differences between the treatments. The addition of 25 percent of zeolite in urea was the most appropriate relation.

Comparação do sistema de monitoramento computadorizado de digestão in vitro com os métodos in vivo e in situ: 2. Uso do resíduo da matéria seca de forragens

ABSTRACT - The objective of this work was to compare the computerized monitoring of the in vitro gas production system with thein vivo and in situ methods. On the comparisons, corn silage with high/low dry matter contents, with/without inoculation, were used. Thedigestibility of silage with high dry matter (DM) content, with/without inoculation, did not present differences among the anal yzed methods.When evaluated apart from the inoculation effect, that silage differed in vitro /gas and in situ methods; however in vivo did not differ. Nevertheless,when analyzed under the inoculation effect, only in i n situ method there was no difference. No differences were found on the silage neutral detergentfiber (NDF) digestibility with high or low DM, inoculated or not, as well as in relation to pH at the end of digestion. In con clusion, the disappearingof DM and NDF determined by the residue of the in vitro/gas system was similar to the others evaluated methods.Key Words: corn silage, gas production, in situ digestion, in vitro digestion, in vivo digestion

Resiliência em sistemas socioecológicos, paisagem rural e agricultura

O presente artigo e resultado de investigacao teorica e conceitual, pesquisa e analise bibliografica sobre a teoria da resiliencia em sistemas socioecologicos, e de uma breve avaliacao de como esses conceitos vem sendo incorporados e inseridos em pesquisas desenvolvidas em areas rurais, com os objetivos de apresentar conceitos sobre resiliencia em sistemas socioecologicos elevantar os temas vinculados a essa questao na literatura. Foram analisados 34 artigos cientificos publicados na ultima decada, a partir de 12 tematicas relacionadas a resiliencia socioecologica. Conclui-se que esforcos de recuperacao socioecologica podem promover a resiliencia em areas rurais. O caminho para garantir essa resiliencia, em diferentes escalas na paisagem rural, envolve praticas mais sustentaveis e novas tecnologias sociais, melhoria dos sistemas de gestao e governanca, valorizacao da cultura e do modo de vida rural e politicas publicas mais efetivas.