Produção e qualidade fisiológica de sementes de feijão-vagem em função de fontes e doses de nitrogênio

Estudaram-se os efeitos da aplicação de cinco doses e três fontes de nitrogênio sobre a produção e a qualidade fisiológica de sementes de feijão-vagem, cv. Macarrão Trepador - Hortivale, no período de setembro/2000 a fevereiro/2001, no Centro de Ciências Agrárias da Universidade Federal da Paraíba, em Areia. O delineamento experimental utilizado foi em blocos casualizados, com os tratamentos distribuídos em esquema fatorial (3 x 5) + 1, correspondendo às fontes (nitrato de cálcio, sulfato de amônio e uréia) e doses (0, 25, 50, 75 e 100kg.ha-1) de nitrogênio, e um tratamento adicional sem adubação (testemunha), com quatro repetições. As fontes nitrato de cálcio e sulfato de amônio, na dose de 100kg.ha-1, e uréia, na dose de 55kg.ha-1 de N, proporcionaram as produções de sementes no feijão-vagem de 2.571, 3.219 e 2.221kg.ha-1, respectivamente. O nitrogênio, em todas as fontes, influenciou positivamente a germinação e o vigor (índice de velocidade de germinação e emergência em campo) da semente do feijão-vagem. As doses de 68,8 e 49kg.ha-1 de N, fontes nitrato de cálcio e uréia foram responsáveis pelos valores máximos para a porcentagem de germinação, 72 e 75%, respectivamente. Para a fonte sulfato de amônio ocorreu aumento linear da porcentagem de germinação, à medida que se elevaram as doses de nitrogênio, sendo que na dose de 100kg.ha-1 obteve-se um porcentual de 84%. O índice de velocidade de germinação apresentou valores mais elevados, 6,0; 7,7 e 6,9 nas doses de 49; 71 e 53kg.ha-1 de N, fontes nitrato de cálcio, uréia e sulfato de amônio, respectivamente. A emergência em campo aumentou linearmente com elevação das doses de N (fonte nitrato de cálcio), sendo a emergência máxima (70%) obtida na dose de 100 kg ha-1 de N em cada fonte. O sulfato de amônio deve ser recomendado como fonte de N, em programas de produção de sementes de feijão-vagem.

Physics, geochemistry and bulk sedimentology on cores from the Peru Basin

Empirical relationships between physical properties determined non-destructively by core logging devices and calibrated by carbonate and opal measurements determined on discrete samples allow extraction of carbonate and opal records from the non-destructive measurements in biogenic settings. Contents of detrital material can be calculated as a residual. For carbonate and opal the correlation coefficients (r) are 0.954 and ?0.916 for sediment density, ?0.816 and 0.845 for compressional-wave velocity, 0.908 and ?0.942 for acoustic impedance, and 0.886 and ?0.865 for sediment color (lightness). Carbonate contents increase in concert with increasing density and acoustic impedance, decreasing velocity and lighter sediment color. The opposite is true for opal. The advantages of deriving the sediment composition quantitatively from core logging are: (i) sampling resolution is increased significantly, (ii) non-destructive data can be gathered rapidly, and (iii) laboratory work on discrete samples can be reduced. Applied to paleoceanographic problems, this method offers the opportunity of precise stratigraphic correlations and of studying processes related to biogenic sedimentation in more detail. Density is most promising because it is most strongly affected by changes in composition.

Sedimentology on cores from the Peru Basin

We investigated surficial sediments for physico-chemical composition from numerous sites of seven study areas in the manganese nodule field of the northern Peru Basin as part of a deep-sea environmental study. Major results from this study are strong variability with respect to water depth, productivity in surface waters, locality, bottom water flow, and seafloor topography. Sediment sites are located mostly in 3900 to 4300 m water depth between the lysocline and the carbonate compensation depth (CCD). Large fluctuations in carbonate content (0% to 80%) determine sediment density and compressional-wave velocity, and, by dilution, contents of opal and non-biogenic material. Mass accumulation rates of biogenic components as well as geochemical proxies (barium and phosphorus) distinguish areas of higher productivity in the northwest near equatorial upwelling and in the northeast close to coastal upwelling, from areas of lower productivity in the west and south. Comparisons between the central Peru Basin area (Discol) and western Peru Basin area (Sediperu) reveals, for the Sediperu area, a shallower CCD, more carbonate but less opal, organic carbon, and non-biogenic material in sediments at the same water depth as well as larger down-core fluctuations of organic carbon and MnO2. Bottom water flow in the abyssal hill topography causes winnowing of material from summits of seamounts and ridges, where organic carbon preservation is poor, to basins where organic carbon preservation is better. Down-core measurements in box cores indicate a three-fold division in the upper 50 cm of the sediment column. An uppermost semi-liquid top layer is dark brown, 5-15 cm thick and contains most of the ferro-manganese nodules. A 5-15 cm thick transition zone of light sediment color has increasing shear strength, lowest opal contents and compressional-wave velocities, but highest carbonate contents and sediment densities. The lowermost layer contains stiffer light gray sediments.