Pore‐size distribution and particle arrangement in fragipan and nonfragipan horizons

Fragipan is a widely distributed subsoil horizon that induces severe limitations to plant growth and land use, mainly because of its high bulk density. In this work, we evaluated the pore‐size distribution through the analysis of the cumulative curve of intruded mercury volume in some soils with fragipan horizons. This approach provides information also about the arrangement of particles, thus we compared the results obtained for fragipan and nonfragipan horizons to relate porosity and particle arrangement with the specific physical properties of fragipans. The total volume of intruded mercury did not allow to discriminate between fragipan and nonfragipan horizons. However, from the variation of the pore volume as a function of the radius, two modal classes of pores were found, coarse and fine, respectively. The fine‐pore class arose from the arrangement of clay particles, and its volume was correlated to clay contents (r = 0.787) and to clay packing density (r = –0.621). The clay fractions in fragipans were less densely packed than in the other B horizons, even if they had similar clay contents. The coarser‐pore modal class is known to arise from the interactions between clay, silt, and sand particles, and its volume was different among horizons. Fragipan had a low volume of this modal pore class. In addition, a packing density for the coarser phase of 0.74, corresponding to a rhombohedral packing, was found only in fragipans. Thus, the low permeability and high bulk density of fragipans are linked to specific arrangements of the particles: an open packing of the clay phase is associated to an extremely dense packing of silt and sand. This combination is not present in any other soil horizon.     

Nutritional efficiency of feed-restricted F1 Holstein/Zebu cows in early lactation

Tropical Animal Health and Production - The quantitative feed restriction of lactating cows has been used in intensive production systems as a strategy to reduce production costs. However, the...     

137Cs Contamination from Chernobyl of Soils in Piemonte (North-West Italy): Spatial Distribution and Deposition Model

¹³⁷Caesium was measured in soils sampled from 101 locationsdistributed across the Piemonte Region (North-West of Italy). The contamination levels found ranged from a few kBq m^-2 to about 60 kBq m^-2, the regional average being of the order of 15 kBq m^-2. The data obtained were interpolated with geostatistical functions in order to obtain a detailed mapof radioactive contamination for the whole region. A second map,representing the rainfall for the period of Chernobyl atmospheric contamination, weighted with the estimated values of air contamination, was produced.The comparison of the two maps and a statistical analysis of the data show that 84% of the ¹³⁷Cs global inventory is due to wet deposition, associated with 9% pre-Chernobyl fallout and a 7% attributed to Chernobyl dry deposition.A deposition model based on a linear relationship betweenwet deposition (D _w) and `weighted rainfall'(R _w) isproposed, applied and tested with available data. On this basisthe following parameters were estimated: scavenging factor, washout ratio, cloud height, dry deposition velocity, mediandiameter of the particles.     

Soil and Sediment Geochemistry of the Iron Quadrangle, Brazil

Soils and sediments around gold ore deposit and mining sites in the Iron Quadrangle present positive As anomalies (median concentrations > 100 mg kg^-1) and wide ranges (< 20 to > 2000 mg kg^-1) even in densely populated areas. These anomalies can be related to geological structures, to hydrothermal ore deposits and to their continuous exploitation over the past three centuries. The paper presents new data on both As geochemistry and soil and sediment geochemistry in general, and discusses consequences of the encountered anomalies, their reasons and potential effects and how they compare with current screening and threshold values. While surface soil As-val-ues are reproducible at a given site, sediment anomalies show a strong seasonal variation that can be explained by tropical hydrologicai variances. Suggestions are presented on how to minimize the As-load in densely populated areas that might otherwise pose a potential health risk.     

Biostimulation of Soil Microbial Activity Through Organic Fertilizer and Almond tree Association

Many studies have confirmed the validity of plant cover and organic farming in ameliorating soil quality. The goal of this study was to investigate the efficiency of rehabilitation practices in a degraded soil ecosystem consisting of: (i) organic or inorganic fertilization; and (ii) presence or absence of almond trees. The experiments were carried out for 2 years in the South of Italy in three fields characterized by different slope (0%, 2%, and 6%). Each field was split up into two parts, one assigned to organic fertilization and the other assigned to mineral fertilization, and planted with almond trees using GF677 or Franco rootstocks. The results showed that the organic fertilization, particularly in the presence of the Franco rootstock, resulted more effective in increasing soil organic matter content and microbial activity especially in the 0% and 2% slopes. However, in the 6% slope, where a lower soil metabolism was observed, an improvement of chemical and biochemical soil properties was generally evident for both fertilization systems. The Franco rootstock improved soil quality and maintaining a good production, whereas the GF677 has exploited more soil resources, resulting in a higher growth and yield; therefore, the use of almond tree with Franco rootstock associated with organic matter application is a useful practice in order to preserve soil quality and to rehabilitate degraded soils. Copyright © 2013 John Wiley & Sons, Ltd.