Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Biology. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Efeito da adubação nitrogenada na produção de mudas de sete-cascas (Samanea inopinata (Harms) Ducke)

Abstract: Understanding seedling nutrition and the use of appropriate substrata for cultivation are essential to define fertilization recommendations. Due to the difficulty in making specific fertilization recommendations, the effect of nitrogen fertilization was tested on the growth and quality of sete-cascas (Samanea inopinata) seedlings. The experiment consisted of nine treatments with three repetitions each and six plastic bags per parcel, in randomized block design. The nitrogen source was ammonium sulfate applied at different levels every 14 or 28 days. The experiment was monitored for twelve months, and then harvested. The following parameters were evaluated: height (H), root collar diameter (D), dry matter of aerial part (MSPA) and root (MSR), total dry matter (MST) and seedling quality indexes H/D, H/MSPA, MSPA/MSR and IQD were calculated. The data were analyzed using factorial and regression analysis. All the tested morphological parameters were significantly affected by the nitrogen fertilization, except for the MSPA/MSR and H/D indexes. Due to the height and diameter importance, it was recommended 0.91 g of ammonium sulfate per seedling every 14 days when cultivated in Red-Yellow Latosol, combined with organic compost.

Avaliação do método centróide para estudo de adaptabilidade ao ambiente de clones de Eucalyptus grandis .

Abstract: The intense genotype x environment interaction present in many cultures make studies of adaptability to specific environments an important part of vegetal improvement programs. The different response of genotypes to favorable and unfavorable environments can be studied using methodologies based on three main strategies: analysis of variance, linear regression and non-parametric statistics. This work presents a new methodology for the study of genotype environment interaction, using principal components analysis, in order to facilitate the recommendation of specific genotypes to certain environments. This methodology, called centroid method, consists in the comparison of cartesian distance values between the genotypes and four ideal references using principal components. It differs from methods based in analysis of variance due to the aiming of genotypes according to environment variation and the facility of genotype identification, dispensing the analysis of several parameters as in methods based on regression. In order to exemplify the use of this method an experiment of Eucalyptus grandis planted in random blocks design and four environments was studied. Four clones of general adaptability were identified besides others of specific adaptation that can also be recommended aiming to capitalize the interaction effect. The results of this study were compared with the ones obtained through other methodologies by Eberhart e Russel (1966) and by Lin and Binns (1988) and allows to conclude that the centroid method was efficient in the identification of differentiated performance E. grandis clones; associated to the easiness of recommendation and ordering of the genotypes into specific adaptability groups.

The effect of the presence of a forage legume on nitrogen and carbon levels in soils under Brachiaria pastures in the Atlantic forest region of the South of Bahia, Brazil

Abstract: The impact of forest clearance, and its replacement by Brachiaria pastures, on soil carbon reserves has been studied at many sites in the Brazilian Amazonia, but to date there appear to be no reports of similar studies undertaken in the Atlantic forest region of Brazil. In this study performed in the extreme south of Bahia, the changes in C and N content of the soil were evaluated from the time of establishment of grass-only B. humidicola and mixed B. humidicola/Desmodium ovalifolium pastures through 9 years of grazing in comparison with the C and N contents of the adjacent secondary forest. The decline in the content of soil C derived from the forest (C3) vegetation and the accumulation of that derived from the Brachiaria (C4) were followed by determining the 13C natural abundance of the soil organic matter (SOM). The pastures were established in 1987, 10 years after deforestation, and it was estimated that until 1994 there was a loss in forest-derived C in the top 30 cm of soil of approximately 20% (9.1 Mg C ha−1). After the establishment of the pastures, C derived from Brachiaria accumulated steadily such that at the final sampling (1997) it was estimated 13.9 Mg ha−1 was derived from this source under the grass-only pasture (0–30 cm). Samples taken from all pastures and the forest in 1997 to a depth of 100 cm showed that below 40 cm depth there was no significant contribution of the Brachiaria-derived C and that total C reserves under the grass/legume and the grass-only pastures were slightly higher than under the forest (not significant at P=0.05). The more detailed sampling under the pastures showed that to a depth of 30 cm there was significantly (P<0.05) more C under the mixed pasture than the grass-only pasture. It was estimated that from the time of establishment the apparent rate of C accumulation (0–100 cm depth) under the grass/legume pastures (1.17 Mg ha−1 yr−1) was almost double that under the grass-only pastures (0.66 Mg ha−1 yr−1). The data indicated that newly incorporated SOM derived from the Brachiaria had a considerably higher C:N ratio than that present under the forest.