Vegetação campestre de areais do Sudoeste do Rio Grande do Sul sob pastejo e com exclusão do pastejo

The objective of this study was to characterize the effects of two grazing management on the natural vegetation, in the edge of sandy patches of Southwest of Rio Grande do Sul State, Brazil. Forty-one community areas of 4.5x9 m, were evaluated: 30 under grazing, and 11 under grazing exclusion. The vegetation composition in each community area was described by visually estimated cover-abundances of vascular plant species and bare-ground. Fifty-three 53 different taxa were identified from 43 genera and 16 families. Axonopus pressus, Elionurus sp., Schizachyrium microstachyum, Bulbostylis sp., Senecio sp., Baccharis coridifolia, Psidium sp., Cardionema ramosissima and Borreria verticillata were present in more than 50% of the communities. Andropogon lateralis was restricted to communities in Alegrete near to the Ibicuí River. Exclosures increase vegetation coverage and diversity, when compared to grazed ones. Natural vegetation under grazing is more susceptible to sandy patch process. Sandy patches under grazing have higher bareground and Elionurus sp., Axonopus pressus and Cardionema ramosissima.O objetivo deste trabalho foi caracterizar os efeitos de dois manejos do pastejo, sobre a vegetação natural do entorno de areais, da região Sudeste do Rio Grande do Sul. Foram estudadas 41 parcelas de comunidades de 4,5x9 m: 30 sob pastejo e 11 em areais excluídos do pastejo. A composição da vegetação foi analisada por meio de inventário das espécies de plantas vasculares, presentes nas parcelas, e por meio de estimativa da abundância/cobertura de cada espécie e substrato exposto. Foram identificadas 53 espécies, distribuídas em 43 gêneros e 16 famílias. Apareceram em mais de 50% das comunidades estudadas: Axonopus pressus, Elionurus sp., Schizachyrium microstachyum, Bulbostylis sp., Senecio sp., Baccharis coridifolia, Psidium sp., Cardionema ramosissima e Borreria verticillata. Andropogon lateralis esteve restrita ao município de Alegrete, próximo ao rio Ibicuí. A exclusão do pastejo aumenta a cobertura vegetal e a diversidade em comparação a comunidades pastejadas. Vegetação natural sob pastejo é mais suscetível ao processo de arenização. Areais manejados sob pastejo apresentam mais substrato exposto e Elionurus sp., Axonopus pressus e Cardionema ramosissima

Aplicação do Método Mesmis para Análise da Sustentabilidade de Sistemas de Produção da Pecuária Familiar em Área do Bioma Pampa no Rio Grande do Sul

Representing a set of very ancient ecosystems, the Pampas Biome features peculiar flora and fauna and great biodiversity, not fully described by the science. Since the Iberian colonization, extensive livestock (beef and sheep) on native grasslands has been the main economic activity of the region. The progressive introduction and expansion of monocultures and pastures with exotic species have led to a rapid degradation and mischaracterization of natural landscapes of the Pampa. The purpose of this article is to assess the sustainability of different livestock production systems of family farmers in Rio Grande do Sul. It was used the Mesmis method for the sustainability analysis of three groups of identified production systems: CN (Natural Grassland), CN+C (Natural Grassland + other cultives) and CN + S (Natural Grassland + Soybean). A significant difference was identified (p <0.05) for “Productivity” attribute between CN + C and CN+ S systems, the first being greater than the second. For other attributes of sustainability there were no significant differences between the studied production systems

FERTILIZATION RESPONSE AND NITROGEN NUTRITION DIAGNOSIS OF A NATURAL GRASSLAND IN SOUTHERN BRAZIL

Natural grasslands found in Campos Biome in Southern Brazil are the main forage source for production approximately 13 million cattle and 5 million sheep. The forage yield is often limited by the soil fertility, which is naturally low. This study aimed to test the response of natural grassland to fertilization and to assess the level of N nutrition index (NNI) achieved with fertilization by using a dilution curve model. The experimental design was a factorial arrangement in sub-divided plots, where the landscape was considered the main plot and fertilization the subplots, with three replicates. In the fertilized treatment were applied 310 kg ha–1 of N, 160 kg ha–1 of P2O5, 160 kg ha–1 of K2O, and 3 Mg ha–1 of dolomitic lime. No fertilization was applied in the non-fertilized treatment (natural soil fertility). Herbage mass was evaluated over 224 days of growth by harvesting all the aboveground plant biomass in a 0.25 m2 quadrat. Herbage mass was higher in the fertilized treatment from 180 to 224 days of growth. At 180 days of growth, herbage mass was 7.8 Mg ha–1 in the fertilized treatment and 3.0 Mg ha–1 in the non-fertilized treatment. Generally, herbage mass accumulation from 83 to 180 days of growth was 3.2 times as high in the fertilized (62 kg ha–1 day–1) than in the non-fertilized treatment (20 kg ha–1 day–1). The N dilution curve model was successfully tested under high and low soil fertility conditions. At 83, 109, and 136 days of growth in the fertilized treatment, the nitrogen nutrition index (NNI) was 95, 103 and 92, respectively; while in the non-fertilized treatment, the NNI was always lower than 52. Therefore, the level of nitrogen nutrition index (NNI) estimated by the N dilution curve model was a good indicator of N availability to the natural grassland, and can be used for assessing the N nutrition status during the growth of natural grassland in Southern Brazil.

Animal performance in oat and Italian ryegrass pastures under leaf lamina biomass levels

O objetivo deste trabalho foi avaliar o efeito de biomassas de lâminas foliares no desempenho animal. Utilizou-se mistura de aveia (Avena strigosa Schreb) e azevém (Lolium multiflorum Lam.), para determinar quantidades adequadas de sua biomassa no manejo da pastagem. Foram realizados dois experimentos, na estação fria de 2002 e 2003. Na avaliação de 2002, os valores de biomassa de lâminas foliares foram de 360 kg ha-1 (baixa) e 630 kg ha-1 (alta). Em 2003, foram obtidas biomassas de 352, 422 e 507 kg ha-1, classificadas como baixa, média e alta, respectivamente. O método de pastejo foi contínuo, com taxa de lotação variada; os animais utilizados foram terneiros da raça Charolês e cruzados com Nelore, com idade inicial de nove meses. As variáveis de produção animal avaliadas, nos dois anos, foram: ganho médio diário, carga animal e ganho de peso vivo por área. As distintas biomassas de lâminas foliares mantidas não são fatores limitantes ao desempenho animal.The objective of this work was to evaluate the effect of different leaf lamina biomass over animal performance. A mixture of oat (Avena strigosa Schreb) and Italian ryegrass (Lolium multiflorum Lam.) was used to determine adequate levels of leaf lamina biomass for pasture management. Two trials were made, in 2002 and 2003 cool seasons. In 2002 evaluation, leaf lamina biomass values were of 360 kg ha-1 (low) and 630 kg ha-1 (high). In 2003, values obtained for leaf lamina biomasses were of 352, 422 and 507 kg ha-1, being classified as low, medium and high, respectively. Grazing method was continuous, with variable stocking rate; testing animals were calves of Charolais breed and its crosses with Nelore breed, with initial age of nine months. Evaluated variables in animal production, in both years, were: average daily gain, stocking rate and live weight gain per area. Leaf lamina biomasses evaluated are not limiting factors to animal performance

Nitrogen efficiency in marandupalisadegrass pastures under increasing nitrogen levels

ABSTRACT: The use of nitrogen (N) in pastoral ecosystems leads to increased productivity, as it allows the plant to elongate its leaves and, therefore, grazing herbivores harvest the green leaves. However, there are very volatile N sources, which can be replaced by ammonium nitrate, which is less volatile and less dependent on the application in rainy days. The treatments are compound of Marandu palisade grass pastures managed under continuous stocking at a canopy height of 25 cm, with different levels of N fertilizer: 0, 75, and 150 kg ha-1year-1, as ammonium nitrate (32% of N), with four replicates (pastures) in a completely randomized design. Nitrogen uptake (54.9, 96.5, 113.8 kg N ha-1) and N nutrition index (0.67, 0.98, 1.15) were different between N level, respectively, 0, 75 and 150 kg ha-1 year-1. The N recovery (58.3, 40.9 %) differed between 75 and 150 kg ha-1 year-1, respectively. The dose of 75 kg N kg ha-1 year-1 results in better N utilization, while the dose of 150 kg N ha-1 year-1 enables greater stocking rate; therefore, requiring less grazing area