Janaina Ribeiro Costa Rouws

Manejo da irrigação associada a coberturas mortas vegetais no cultivo orgânico da beterraba

Praticas agricolas orgânicas, como a cobertura do solo com palha, foram testadas em area irrigada por gotejamento na Baixada Fluminense, no Estado do Rio de Janeiro. O cultivo de inverno da beterraba nesta regiao e favorecido por temperaturas mais amenas, coincidindo com a epoca de maior disponibilidade do produto no Estado. No cultivo da beterraba, foram adotados tres tipos de cobertura do solo e seis lâminas de irrigacao (0; 29; 48; 78; 100 e 148% da ETc) determinadas com base no balanco de agua no solo utilizando a tecnica da TDR. O delineamento estatistico adotado foi blocos casualizados, com seis tratamentos e quatro repeticoes. Sob cobertura morta de Pennisetum purpureum, de Gliricidia sepium e na ausencia de cobertura morta, os valores maximos relativos de EUA, no cultivo de beterraba, foram de 21,00; 32,90 e 17,90 kg m-3, respectivamente. A maior e a menor lâmina de irrigacao acumulada para cada tipo de manejo foram de 2.746 e 951 m3 ha-1 nas parcelas sem cobertura morta. Em comparacao, as parcelas com cobertura do solo reduziram em 34,5 e 10,5% as lâminas acumuladas, respectivamente. Os valores acumulados de nitrogenio nas partes das plantas foram maiores no cultivo sob cobertura morta de G. sepium, indicando vantagens desta pratica cultural associada a irrigacao por gotejamento.

Forage intake and botanical composition of feed for cattle fed Brachiaria/legume mixtures

A key contribution to study the cycling of nutrients in soil/plant/animal systems is the evaluation of the consumption of forage and their nutrients by cattle. The objective of this study was to test techniques to evaluate faecal production, in vitro digestibility, forage consumption and the proportion of legume in the acquired diet. Five Zebu steer calves were confined and fed five diets of different combinations of Brachiaria dictyoneura and Desmodium ovalifolium. All quantities of faeces were collected per animal and these values were found to compare favourably with those derived from using the chromium oxide technique. In vitro digestibility ranged from 7 to 10% higher than the actual in vivo digestibility. Faecal samples from steers fed with diets with 25% or more of grass in the mixture were found to be depleted in δ13C between 1.7 and 2.1‰, but no depletion was observed when the diet was 100% D. ovalifolium. There was a positive linear regression (r2 = 0.97***) of the δ13C of the diet with the δ13C of faeces, but if the acquired diet contained a very high proportion of legume, the legume content could be underestimated by as much as 10%. None of the internal indicators, such as lignin or ash content of the diets, were useful to predict feed intake, but the chromium oxide external indicator performed satisfactorily. The 13C analysis of the faeces was an effective predictor of the proportion of the legume in the consumed diet.

Vegetative and productive aspects of organically grown coffee cultivars under shaded and unshaded systems

Although Coffea arabica species has its origin in the African understories, there is great resistance on the part of the Brazilian producers for growing this species under agroforestry systems as they fear that shading reduces production. This study aimed at evaluating some vegetative traits and the productivity of organically grown coffee (Coffea arabica L.) cultivars under shaded and unshaded systems. Twelve treatments consisting of two cultivation systems (shaded and unshaded) and six coffee cultivars were arranged in randomized blocks with four replicates, in a split-plot scheme. Shading was provided by banana (Musa sp.) and coral bean plants (Erythrinaverna). Shading delayed fruit maturation. Late maturation cultivars, such as the Icatu and the Obata, matured early in both cultivation systems, while medium and early maturation cultivars presented late maturation. Cultivation in the shaded system increased the leaf area and the number of lower branches, decreased the number of productive nodes per branch, and increased the distance between the nodes and the number of leaves present in the branches. Cultivation in the unshaded system presented greater number of plants with branch blight in relation to plants grown in the shade. The productivity of the cultivars was not different, at 30.0 processed bags per hectare in the shaded system, and 25.8 processed bags per hectare in the unshaded system. The most productive cultivars in the shaded system were the Tupi, the Obata, and the Catuai, while no differences between cultivars were obtained in the unshaded system.

Frações oxidáveis do carbono orgânico total e macrofauna edáfica em sistema de integração lavoura-pecuária

The increasing level of land degradation has led to the adoption of agricultural management practices that seek to combine agricultural production and soil conservation. Among these, the practice of Crop-Livestock Integration (CLI) has intensified in West-Central Brazil. In order to assess the long-term effect of the CLI system and seasonality on the community of soil macrofauna and oxidizable fractions of total organic C in croplands and the Cerradao (Brazilian tropical savanna), a study was developed at the Cabeceira Farm in the municipality of Maracaju, State of Mato Grosso do Sul, which measured the effect of CLI on oxidizable fractions of total organic C and soil macrofauna. The CLI system has been used in this area since 2003. The soil was identified as a Latossolo Vermelho (Ferrasol), on flat land. The areas sampled have the following history of use: soybean/corn + brachiaria grass/cotton/oat + pasture/soybean/implantation of pasture/pasture. Sampling was carried out in two seasons, dry and wet. In the dry season, the crops were pasture, corn+brachiaria grass and cotton; in the rainy season there were corn+brachiaria grass, cotton, and soybeans. Thus, the areas in the two evaluation periods were pasture/corn, corn+brachiaria/cotton, cotton/soybeans, and an area of native Cerrado. Sampling was performed at the depths of 0-10, 10-20, and 20-30 cm, and the following determinations were made: analysis of soil macrofauna, particle size fractionation of soil organic matter (SOM), and oxidizable fractions of total organic C. The areas do not have an experimental design as this is an observational study. Data were compared by the Kruskal Wallis test at 5 % probability and through analysis of redundancy. Compartmentalization of SOM can be used to assess the quality of management, with the most sensitive compartments being the F1 and F2 fractions in the assessment of oxidizable fractions. These fractions are more labile in the soil, whereas the F3 and F4 fractions are more recalcitrant. Isoptera (termites) may be acting as a wetting agent of organic matter in the Cerrado area, contributing to higher levels of F3 and F4, compared to F1 and F2, in the dry season. This pattern was only observed in the Cerrado area since in the production areas, Isoptera is controlled by management practices. The lack of these insects in the CLI system may be reducing the stabilization of SOM in the F3 and F4 fractions.

EROSIVIDADE DAS CHUVAS ASSOCIADA A PERÍODOS DE RETORNO E PROBABILIDADE DE OCORRÊNCIA NO ESTADO DO RIO DE JANEIRO

O conhecimento da erosividade das chuvas associada a probabilidade de ocorrencia e ao periodo de retorno pode contribuir para o planejamento conservacionista de uma regiao, em medio e longo prazo. A fim de gerar informacoes para melhor utilizar modelos e controle da erosao, dados de chuvas de 30 series pluviograficas e pluviometricas, abrangendo 25 municipios, entre 1933 e 2006, foram estudados quanto a adequacao das series e do calculo da probabilidade de ocorrencia teorica (P) e periodo de retorno (T) da erosividade das chuvas (EI30 e KE>25), para o Estado do Rio de Janeiro. Foi feita a espacializacao do potencial erosivo associado aos periodos de retorno de 2, 5, 10, 20, 50 e 100 anos para todo o Estado. A erosividade anual media (EI30) ou fator R da USLE para qualquer localidade no Estado do Rio de Janeiro pode ser igualada ou superada pelo menos uma vez, em media, em um periodo de 1,8 a 2,1 anos, com faixa de 48,5 a 54,9 % de probabilidade de ocorrencia teorica. As localidades que apresentam maior erosividade associada aos periodos de retorno estao situadas nas mesorregioes Metropolitanas e em partes das mesorregioes Sul e Centro Fluminense. Foi possivel identificar de oito a 12 regioes homogeneas, quanto a distribuicao espacial da erosividade associada aos periodos de retorno de dois para 100 anos no Estado. De modo geral, a maior variacao da distribuicao espacial da erosividade apresenta-se na faixa de periodo de retorno de dois a cinco anos.

Dinâmica de rizóbios em solo do cerrado de Roraima durante o período de estiagem

The biological nitrogen fixation in legumes is performed by a group of bacteria known as rhizobia. The survival of these bacteria in soils is affected by several factors, such as temperature, drought and soil fertility. This study was performed to evaluate the dynamics of rhizobia in the soil after soybean cultivation and during a dry season in the cerrado of Roraima. Three areas were sampled: i) native cerrado as reference; ii) an area previously cultivated with soybean for one season; and iii) another one cultivated for two seasons also with soybean. The soil was sampled at a depth of 0-10 cm in five times (0, 45, 90, 135 and 180 days) during the dry season (September 2006 to March 2007). The rhizobial density in the soil was evaluated by the most probable number method with infection of soybean and cowpea plants. It was observed very low number of soybean nodulating bacteria in the reference area, but a high density, of up to several hundred rhizobia capable to nodulate cowpea was measured in this same area. Cropping of soybean with inoculated seeds increased rhizobial density evaluated by both trapping hosts. In cropped areas, an intense reduction of rhizobium density was observed just after soybean harvest, and this reduction continued until the end of the period of evaluation. It was concluded that soybean cultivation increases the density of rhizobial in the cerrado soil; however, this density is drastically reduced, during the dry season, by 99% at the end of the dry period.

Superação de Dormência de Sementes de Albizia pedicellaris (DC.) L. Rico

The study aimed to evaluate the efficiency of seeds dormancy breakage methods for Albizia pedicellaris in laboratory. Seeds were treated with ten pre-sowing treatments: chemical scarification using sulfuric acid for 5, 10, 15 and 30 minutes, physical scarification followed or not by immersion in water for 6, 12 and 24 hours, thermal shock and control. Completely randomized design was used with four replications of 25 seed per experimental unit. The followings variables were evaluated: germination percentage, speed germination index, normal seedlings number, abnormal seedling number, and mortality. The results indicate that the most efficient method to overcome dormancy was mechanical scarification followed or not by immersion for 6 or 12 hours or immersion in sulfuric acid for 30 minutes.

Nutrient input on rocket growth and soil microbial activity in alley cropping of pigeon pea

The effects of organic fertilization combining cattle manure and pigeon pea shoots on the culture of rocket, planted with one or two plants per hole, including soil microbial biomass carbon, soil respiration, the metabolic quotient, soil fumigation labile carbon, and the dry matter content and total N, K, P, Ca and Mg contents in the leaves and roots of rocket were investigated. The experimental design was randomized blocks in a 2 × 2 × 2 factorial experiment: 0 and 160 kg ha-1 N from cattle manure, 0 and 160 kg ha-1 N from pigeon pea shoots, and one or two plants per hole, with three replicates. The most significant and positive correlations were obtained between leaf K × soil respiration, microbial biomass × leaf N and root Ca × metabolic quotient. The use of 160 kg ha-1 N from cattle manure along with 160 kg ha-1 N from pigeon pea shoots with two plants per hole resulted in a lower relative loss of C-CO2; the same result was found for the treatment of two plants per hole fertilized with 160 kg ha-1 N from cattle manure. Increased leaf and root N contents were observed in the treatment that combined two plants in each plot, fertilized with 160 kg ha-1 N from pigeon pea shoots, whereas the highest dry matter content was obtained by using one plant per hole, specifically: combining one plant per hole without fertilization; one plant per hole fertilized with 160 kg ha-1 N from pigeon pea shoots; and one plant per hole fertilized with 160 kg ha-1 N from cattle manure and pigeon pea shoots.