Scielo RSS <![CDATA[Scientia Agricola]]> vol. 71 num. 3 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Cowpea symbiotic efficiency, pH and aluminum tolerance in nitrogen-fixing bacteria</b>]]> Cowpea (Vigna unguiculata) cultivation in northern and northeastern Brazil provides an excellent source of nutrients and carbohydrates for the poor and underprivileged. Production surplus leads to its consumption in other regions of Brazil and also as an export commodity. Its capacity to establish relationships with atmospheric nitrogen-fixing bacteria is crucial to the reduction of production costs and the environmental impact of nitrogen fertilizers. This study assessed the symbiotic efficiency of new strains of symbiotic nitrogen-fixing bacteria with cowpea and their tolerance to pH and aluminum. Twenty-seven strains of bacteria from different soils were evaluated under axenic conditions. These strains were compared to the following inoculant strains: INPA03-11B, UFLA03-84 and BR3267 and two controls that were not inoculated (with and without mineral nitrogen). Six strains and the three strains approved as inoculants were selected to increase the dry weight production of the aerial part (DWAP) and were tested in pots with soil that had a high-density of nitrogen-fixing native rhizobia. In this experiment, three strains (UFLA03-164, UFLA03-153, and UFLA03-154) yielded higher DWAP values. These strains grow at pH levels of 5.0, 6.0, 6.8 and at high aluminum concentration levels, reaching 10(9) CFU mL-1. In particular UFLA03-84, UFLA03-153, and UFLA03-164 tolerate up to 20 mmol c dm-3 of Al+3. Inoculation with rhizobial strains, that had been carefully selected according to their ability to nodulate and fix N2, combined with their ability to compete in soils that are acidic and contain high levels of Al, is a cheaper and more sustainable alternative that can be made available to farmers than mineral fertilizers. <![CDATA[<b>Plant densities and modulation of symbiotic nitrogen fixation in soybean</b>]]> Soybean nitrogen (N) demands can be supplied to a large extent via biological nitrogen fixation, but the mechanisms of source/sink regulating photosynthesis/nitrogen fixation in high yielding cultivars and current crop management arrangements need to be investigated. We investigated the modulation of symbiotic nitrogen fixation in soybean [Glycine max (L.) Merrill] at different plant densities. A field trial was performed in southern Brazil with six treatments, including non-inoculated controls without and with N-fertilizer, both at a density of 320,000 plants ha−1, and plants inoculated with Bradyrhizobium elkanii at four densities, ranging from 40,000 to 320,000 plants ha−1. Differences in nodulation, biomass production, N accumulation and partition were observed at stage R5, but not at stage V4, indicating that quantitative and qualitative factors (such as sunlight infrared/red ratio) assume increasing importance during the later stages of plant growth. Decreases in density in the inoculated treatments stimulated photosynthesis and nitrogen fixation per plant. Similar yields were obtained at the different plant densities, with decreases only at the very low density level of 40,000 plants ha−1, which was also the only treatment to show differences in seed protein and oil contents. Results confirm a fine tuning of the mechanisms of source/sink, photosynthesis/nitrogen fixation under lower plant densities. Higher photosynthesis and nitrogen fixation rates are capable of sustaining increased plant growth. <![CDATA[<b>Poultry offal meal in broiler chicken feed</b>]]> An outstanding feature of poultry production that provides animal protein yield for human feeding is its short production cycle. This characteristic has a linear relationship with waste production. Increasing the inclusion of this residue in diets in the near future is desirable in step with the growth of poultry production since it offers a better environmental and nutritional alternative to current methods. We evaluated the effects on the performance and carcass characteristics of broiler chickens produced by the inclusion of poultry offal meal (POM) in their feed. Treatments consisted of a control diet (corn, Zea mays and soybean, Glycine max) and four diets with inclusion of 30, 60, 90 and 120 g kg-1 of POM. The diets were formulated based on the level of digestible amino acid once categorized as isocalcic, isophosphoric, isosodic, isoenergetic and isonutritive for protein, methionine+cystine, lysine and threonine. The feed's electrolytes were corrected so that each diet had the same electrolytic balance. The variables analyzed were feed intake, weight gain, feed conversion ratio, body weight, carcass yield, chicken cut yield and abdominal fat. Feed intake was not affected by the quantities of POM added. The weight gain, feed conversion, carcass yield and noble cuts presented quadratic responses to the treatments. Abdominal fat increased linearly. The performance of the poultry, and carcass characteristics were maximized by the inclusion of 53 and 65 g kg-1, respectively, of POM in the diet, and the inclusion of 120 g kg-1 of POM provided greater disposition of abdominal fat. <![CDATA[<b>Reevaluation of the digestible lysine requirement for broilers based on genetic potential</b>]]> Broiler strains available in the poultry industry present different requirements for dietary lysine due to their different growth potentials as a result of their genetic makeup. This study aimed to determine the model parameters for maximum nitrogen retention (NRmaxT), the nitrogen maintenance requirement (NMR) and the efficiency of lysine utilization (bc-1) to reevaluate the lysine (Lys) requirements of male and female broilers. Nitrogen balance trials were performed during three periods (I: 6-21 days, II: 22-37 days, and III: 38-53 days). Seven treatments were used for males and females; the treatments consisted of seven diets with protein levels ranging from 61 to 364 g kg-1 dry matter, with Lys being limiting in the dietary nitrogen (4.91 g of Lys in 16 g of N). Nitrogen intake (NI), excretion (NEX), deposition (ND, ND=NI-NEX) and retention (NR, NR=ND+NMR) values were obtained. The NMR was represented by the exponential relationship between NEX and NI. The NRmax T and bc-1 were estimated by the exponential fit between ND and NI. The NRmax T, bc-1, and NMR values were combined in a model to estimate Lys intake by simulating different percentages of the NRmaxT. The Lys intake estimates were 581, 1,538, and 2,171 mg day-1 for males and 512, 1,340, and 1674 mg day-1 for females during periods I, II, and III, respectively. Due to the flexibility of the model, it is possible to calculate the Lys intake for percentages of NR in the range of practical performance data. <![CDATA[<b>Physicochemical, microbiological and sensory assessments of Italian salami sausages with probiotic potential</b>]]> Probiotics are live microorganisms that confer a health benefit on the host by improving the intestinal microbial balance. We evaluated the viability of Lactobacillus acidophilus (La) and Bifidobacterium lactis (Bl) probiotics and their effects on the technology and sensorial characteristics of fermented sausage. The presence of probiotic cultures reduced water activity and promoted faster pH reduction in the salamis, which presented pH values between 4.71 and 5.23 and water activity between 0.84 and 0.89. Lactic acid content ranged between 0.19 and 0.29 g, and the samples lost up to 35 % of their weight during ripening. As regards color, no differences were found between the probiotic salamis and the control, presenting an overall mean of 40.85 for L* (lightness), 14.48 for a* (redness) and 6.46 for b* (yellowness). High consumer acceptance was observed for the probiotic salamis, which showed an average acceptance of approximately 7.0 on a nine-point hedonic scale for all attributes evaluated, with no differences (p < 0.05) when compared with the control. The performance of La was better, as the salamis treated with this microorganism presented less weight loss, better acceptance and greater purchase intention. Flavor and texture were the attributes that most influenced sensory acceptance. Salamis supplemented with probiotic cultures may be a viable option for the formulation of fermented sausages in the food industry. <![CDATA[<b>Individual tree growth models for eucalyptus in northern Brazil</b>]]> The diameter and height growth model is one of three submodels used for simulating individual tree growth. In Brazil, there are few studies on the dimensional growth of individual trees be they native or exotic species, despite their potential. This study aimed to evaluate diameter and height growth models for individual trees for eucalyptus stands and to validate the best fitting model. Tree diameter and height data were obtained from 48 permanent plots of unthinned stands of Eucalyptus grandis × Eucalyptus urophylla hybrid located in northern Brazil. The evaluation of the diameter and height growth models was based on adjusted coefficient of determination, standard error of estimate as a percentage, trend, root mean square error and Akaike Information Criterion. Analysis also included distribution of residual percentage, statistical significance and signs of the coefficients. The Lundqvist-Korf model provided the most accurate estimates for diameter and height growth, in comparison with the other models, providing better statistical values, greater proximity to observed values and better distribution of residual percentages. The use of this type of model is feasible and can result in significant improvements in the accuracy of yield estimates. <![CDATA[<b>Seed size-number trade-off in <i>Euterpe edulis</i> in plant communities of the Atlantic Forest</b>]]> Investigations of seed size and number differences among plant populations growing in contrasting habitats can provide relevant information about ecological strategies that optimize reproductive effort. This may imply important consequences for biodiversity conservation and restoration. Therefore, we sought to investigate seed size-number trade-off in Euterpe edulis populations growing in plant communities in the Brazilian Atlantic Forest. Seed dry mass and seed number per bunch were evaluated in 2008 and 2009 in large remnants of the Seasonally Dry Forest, Restinga Forest and Atlantic Rainforest in southeastern Brazil, in 20 individuals per site and year. Seed size and seed number varied among forest types, but a seed size-number trade-off was neither observed within nor among populations. Positive association between seed size and number was found in the Atlantic Rainforest, and reduced seed crop was not accompanied by heavier seeds in the Restinga Forest. Seed dry mass declined in 2009 in all three forest types. Compared to seed number in 2008, palms of both the Restinga Forest and the Atlantic Rainforest produced in 2009 higher yields of smaller seeds - evidence of between years seed size-number trade-off -, while the Seasonally Dry Forest population produced a reduced number of smaller seeds. Such a flexible reproductive strategy, involving neutral, positive, and negative associations between seed size and number could enhance the ecological amplitude of this species and their potential to adapt to different environment conditions. <![CDATA[<b>Efficiency in the use of phosphorus by common bean genotypes</b>]]> Common bean (Phaseolus vulgaris L.) is frequently grown in weathered soils with low phosphorus (P) availability, and this is one of the main limitations on its production. This study aimed to assess 20 common bean genotypes in a hydroponic system to select the best P concentration for inducing nutritional deficiency and to classify the genotypes in terms of nutrient utilization efficiency. The concentrations of P applied were 8.00, 4.00, 2.00 and 0.05 mg L¹. At 21 days, in the plot subjected to an application of the most severe stress, the 0.05 mg L¹ dose of P, had smaller plant size and early leaf abscission was observed. The 4.00 mg L¹ dose of P was the most efficient in inducing stress for discrimination of cultivars in terms of efficiency of use of P. The following genotypes: IAPAR 81, Carioca Comum, IAC Carioca Tybatã, IAC Imperador and G 2333 stood out as being efficient and responsive to P, while the two cultivars DOR 364 and Jalo Precoce were the most inefficient and unresponsive. <![CDATA[<b>Recurrent mass selection for upright plant architecture in common bean</b>]]> Plant with a more upright architecture offers many advantages to farmers. Recurrent mass selection (RS) programs for carioca type common bean have been implemented for the purpose of obtaining new lines that will generate the high yields that are associated with upright plant archi tecture. This study aimed to assess the efficiency of recurrent mass selection (RS) for upright plant architecture in common bean (Phaseolus vulgaris) and the effect of RS on grain yield and to verify whether or not there is still variability in the population that favors continuing selection programs, using information obtained from progenies evaluated in cycle five (CV) and cycle eight (CVIII) of the RS program. Mass selection for more upright plants was performed visually in the "S0" generation before flowering. Progenies S and Swere evaluated in 2009 (CV) and 2011 (CVIII). Heritability (h²;) and RS progress were estimated using adjusted means. After eight selection cycles, the population subjected to RS still had enough genetic variability to achieve continued success through recurrent selection. The RS progress was 1.62 % per cycle for the growth habit scores and 6.81 % for grain yiel. <![CDATA[<b>Clay mineralogy and magnetic susceptibility of Oxisols in geomorphic surfaces</b>]]> Studies analyzing the variability of clay minerals and magnetic susceptibility provide data for the delineation of site-specific management areas since many of their attributes are important to agronomy and the environment. This study aimed to evaluate the spatial variability of clay minerals, magnetic susceptibility, adsorbed phosphorus and physical attributes in Oxisols of sandstones in different geomorphic surfaces. For that purpose, soil samples were collected every 25 m along a transect located within the area where the geomorphic surfaces were identified and mapped. The transect occupied the central portion of 500 ha, where it was also sampled for density purposes with one sample per six hectares. Soil samples were collected at a depth of 0.0-0.2 m. The results of the physical, chemical, mineralogical and magnetic susceptibility analyses were subjected to statistical and geostatistical analyses. The nature of the clay minerals and magnetic susceptibility was dependent on the variation of the soil parent material. High values of magnetic susceptibility were associated with the presence of maghemite and magnetite of coarse size. The spatial variability of crystallinity and the content of Fe oxides, as well as magnetic susceptibility, were dependent on the age of the geomorphic surfaces. The youngest surface had greater spatial variability of these attributes. The iron (goethite and hematite) and aluminum (gibbsite) oxides in the youngest geomorphic surface influenced the low values of soil density and high values of total pore volume, micropores and P adsorption. The characterization of the spatial variability of Fe oxides and susceptibility allowed for the delineation of homogeneous areas.