High water consumption during irrigation is one of the main problems in agriculture. The preparation of a material that prolongs the water retention capacity of the soil is important. This article aimed to prepare superabsorbent hydrogels by the complexation of chitosan (CHI), with high degree of deacetylation (DD), and carboxymethylcellulose (CMC), with high degree of substitution (SD). Different parameters (concentration and polymeric solutions addition order, polysaccharides’ ratio, pH) were studied. Morphology, thermal stability, chemical composition, mechanical strength, and swelling kinetics of hydrogels in water were evaluated. A hydrogel formation mechanism was discussed and proposed. Results showed that most samples prepared at acid pH disintegrated during swelling test. The morphology of the hydrogels varied with the pH. It was obtained superabsorbent hydrogels (swelling > 400%) based on CMC (SD = 2.23) and CHI (DD = 92%), at basic pH, with good compression strength, and applicable as soil conditioner. The best sample was the one prepared with CMC:CHI = 1:2, polymeric solutions 1.5% m/v and pH 8.

C. Ducati, M.A. Neres, D.D. Castagnara, P.S.R. Oliveira, D. Weirich, G.M. Silva, and S.M.M. Sunahara. 2015. Forage potential of oat Iapar 61 alone or in association with birdsfoot trefoil. Cien. Inv. Agr. 42(3): 341-351. The objective of this study was to evaluate the structural characteristics, dry matter production, residual mass, chemical composition and in vitro dry matter digestibility of Iapar 61 black oat (Avena strigosa cv Iapar 61) pasture, both in isolation and in association with birdsfoot trefoil (Lotus corniculatus L., cv. St. Gabriel), under different forms of management in three growth cycles. A randomized block design was used with split plots in time with four treatments: conventional tillage oats, oat tillage, oats associated with birdsfoot trefoil and single birdsfoot trefoil, with three periods of evaluation and four replications. The apical meristem of oats increased from the first to the second cycle. The dry matter production of single birdsfoot trefoil was 579.65 kg on average, and the oats tillage production was 2597.78 kg. Oats exhibited high nutritional value before the first grazing in all treatments; however, at the end of its cycle, the association with birdsfoot significantly increased the crude protein content of the forage. The in vitro dry matter digestibility was similar between crops and decreased in the third cycle. Birdsfoot increased the nutritional value of oats at the end of the oat life cycle.

C. Ducati, M.A. Neres, D.D. Castagnara, P.S.R. Oliveira, D. Weirich, G.M. Silva y S.M.M. Sunahara. 2015. Potencial forrajero de avena Iapar 61 solo o en combinación con la lotera. Cien. Inv. Agr. 42(3): 341-351. El objetivo de este estudio fue evaluar las características estructurales, la producción de materia seca, masa residual, composición química y digestibilidad de la materia seca in vitro de la avena negra (Avena strigosa) Iapar 61, sola y en asociación con la lotera (Lotus corniculatus L., cv. San Gabriel), bajo diferentes formas de manejo, en tres ciclos de crecimiento. El diseño experimental fue de bloques al azar con parcelas divididas en el tiempo, con tres tratamientos: avena con siembra convencional, avena con siembra directa, avena asociado con la lotera con tres periodos de evaluación y cuatro repeticiones. El meristema apical de la avena fue incrementándose desde la primera hasta el segundo ciclo. La producción de materia seca de la lotera sola fue baja en todos los períodos con una media de 579,65 g kg-1, mientras que la producción de avena sola con siembra convencional fue de 2.597 kg ha-1. La avena reveló un alto valor nutricional antes del primer pastoreo en todos los tratamientos; sin embargo, al final de su ciclo, la asociación con lotera contribuyó a elevar el contenido de proteína cruda del forraje, debido a que ésta es la etapa final de su ciclo. La digestibilidad de la materia seca in vitro fue similar entre los cultivos evaluados con una disminución en el tercer ciclo. La asociación promovió mejora el valor nutricional de la avena asociados con lotera al final del ciclo de la avena.

A viscosimetria é um procedimento experimental simples e pouco oneroso, que pode fornecer informações valiosas sobre o volume hidrodinâmico e a conformação de macromoléculas em solução, num determinado solvente, em uma dada temperatura. Os parâmetros viscosimétricos podem ser matematicamente calculados por extrapolação gráfica, cuja execução experimental é mais demorada. Em contrapartida, é possível que a determinação seja feita por um único ponto. Foi realizado um estudo viscosimétrico, em solução, de polibutadieno e de copolímeros aleatórios de 1,3-butadieno e 1-octeno, (obtidos com diferentes razões, em massa, de 1,3-butadieno/1-octeno (Bd/Oct = 99/1 e 97/3) utilizando-se tolueno e hexano, a 30 ± 0,1 °C. A massa molar das amostras foi determinada por cromatografia de exclusão por tamanho (SEC). Os cálculos por extrapolação gráfica foram feitos empregando-se as equações de Huggins, Kraemer e Schulz-Blaschke e a determinação por único ponto pelas equações de Schulz-Blaschke, Solomon-Ciuta e Deb-Chanterjee. O método de determinação por um único ponto mostrou-se eficiente para os sistemas estudados. Avaliou-se a qualidade dos solventes por meio da determinação das constantes viscosimétricas de Huggins e Kraemer. Ambos os solventes utilizados podem ser classificados como bons para os polímeros analisados (k h<0,5 e k k<0), sendo o hexano o melhor, uma vez que as viscosidades intrínsecas determinadas para todas as amostras neste solvente foram maiores do que as determinadas em tolueno. Por meio dos valores de viscosidade intrínseca e do parâmetro g' (razão entre as viscosidades do polímero ramificado e do linear) foi confirmada a existência de ramificações na cadeia polimérica já que g'<1 e os valores de viscosidade intrínseca são inferiores aos obtidos para o homopolímero.

Viscosimetry is a simple, inexpensive characterization method that provides valuable information about the hydrodynamic volume and conformation of macromolecules in solution, in a solvent, at a given temperature. The viscosimetric parameters can be mathematically calculated by graphic extrapolation, in time-consuming experimental tests. It is possible, however, to achieve results by a single point determination. In this work we used the two calculation methods employing a series of six equations: Huggins, Kraemer and Schulz-Blaschke, by graphic extrapolation; and Schulz-Blaschke, Solomon-Ciuta and Deb-Chanterjee, by a single point determination, for solutions of polybutadiene and of random copolymers of 1,3-butadiene and 1-octene, with different mass ratios (Bd/Oct = 99/1 and 97/3). The viscosimetric determinations were carried out in toluene and hexane, at 30 ± 0.1 °C. The weight average molecular mass was determined by size exclusion chromatography (SEC). The values of intrinsic viscosity and of some constants indicated that both toluene and hexane were good solvents for the samples, with hexane being better owing to the higher intrinsic viscosities when compared to the former. It was also observed that the method of calculation by a single point was valid. By means of the intrinsic viscosity values and the parameter g' (ratio between the viscosities of branched and linear polymer) the occurrence of branching in the copolymer chain was suggested because g'<1 and the values of intrinsic viscosity were lower than those obtained for the homopolymer.

The aim of this work is to evaluate the influence of octene-1 incorporation in the polybutadiene chain on the polymerization reaction and polymer characteristics. Thus, copolymerization of butadiene-1,3 with octene-1 using a Ziegler-Natta ternary catalyst based on neodymium was performed. The weight ratios of butadiene-1,3/α-olefin 100/0, 99/1, 97/3, 95/5, 90/10, 80/20 and 70/30 were evaluated. The copolymers were characterized by size exclusion chromatography (SEC), infrared spectroscopy (FTIR) and thermogravimetric analysis (TG). The results showed that the degradation temperature (Tmax) was not affected by the addition of alpha-olefin, while the thermal behavior has undergone significant changes. The polymer microstructure was not influenced by the increasing of octene-1 content. However, a tendency to molecular mass increase was observed with the increasing of octene-1 content. It was also observed a trend in reduction of the polymerization conversion as the octene-1 content increased.

A espécie Bromus auleticus é uma gramínea perene nativa, com potencial para produção de forragem no outono-inverno, período de maior carência alimentar dos rebanhos bovino e ovino do sul do Brasil. O objetivo deste trabalho foi verificar a presença de microorganismos associados a sementes de B. auleticus, em função do momento de coleta, na planta e no solo. Os trabalhos de campo foram conduzidos na Embrapa Pecuária Sul, Bagé, estado do Rio Grande do Sul, em área semeada no ano de 1995. Em novembro de 2002 foram colhidas manualmente as panículas de 30 plantas representativas da população, das quais foram separadas aleatoriamente 900 sementes cheias. De outra forma, na mesma área experimental, realizaram-se coletas de solo nos primeiros dias dos meses de janeiro, fevereiro, março e abril, das quais foram separadas manualmente 200, 300, 200 e 60 sementes, respectivamente. Todas as sementes foram analisadas para sanidade utilizando-se o método do papel de filtro (Blotter test), com incubação a 20ºC, 12 horas de luz, por um período de sete dias. Ocorreram vários fungos, principalmente Alternaria spp., associados a sementes de B. auleticus que ainda estavam presas à planta-mãe, com uma tendência de diminuição dessa contaminação após o desprendimento natural. Foi observada uma alta incidência do fungo Trichoderma em sementes coletadas do solo, provavelmente constituindo uma associação benéfica entre essas espécies. Estima-se que o fungo Trichoderma seja antagônico a outros fungos potencialmente patogênicos a sementes de Bromus auleticus, como Alternaria spp.

Bromus auleticus is a native perennial grass, with potential to produce forage in the autumn-winter, a period when animal feed is scarce in the south of Brazil. The objective of this work was to verify microorganisms associated with seeds of B. auleticus, in function of the moment of collection, in the plant and in the soil. Field studies were conducted in "Embrapa Pecuária Sul", Bagé - state of Rio Grande do Sul, in an area sowed in 1995. Panicles of thirty representative plants were harvested in November, 2002, obtaining 900 seeds. Following another procedure, in the same experimental area, soil samples were collected in the first days of January, February, March and April; 200, 300, 200 and 60 seeds were thus obtained, respectively. All seeds were analyzed by the blotter test, with incubation at 20ºC, 12 hours of light, for a period of seven days. Several fungi were observed, mainly Alternaria spp., associated with seeds of B. auleticus that were still attached to the mother plant. There was a tendency for that contamination to decrease after natural detachment. A high incidence of Trichoderma was also observed in seeds of B. auleticus present in the soil, probably constituting a beneficial association between these species. It is considered that Trichoderma may be antagonistic to other fungi that are potentially pathogenic to seeds of Bromus auleticus, such as Alternaria spp.