María Jose Fernández Sanjurjo

Pedogenesis induced by Genista aetnensis (Biv.) DC. on basaltic pyroclastic deposits at different altitudes, Mt. Etna, Italy

The paper deals with the role of Etnean broom [Genista aetnensis (Biv.) DC.] on the early stages of pedogenesis on basaltic pyroclastic deposits (Mt. Etna, Italy) of different age and altitude previously not vegetated. After a few decades, this plant has been capable to arrest erosion and produce some soil features in both Entisols. The soil of Mts. Rossi, at a lower altitude, formed from a centenary parent material and hosted a broom plantation of about 50 years old. Here, the regimes of soil moisture (ustic) and temperature (mesic) limited the diffusion of the grass to the projection of the broom crowns, but favoured the diffusion of microorganisms and pedofauna. These conditions favoured a generalised alteration of the parent material and induced a certain horizon organisation. The soil of Mt. Vetore, at higher altitude, formed from a millenary parent material, and hosted a broom plantation of about 35 years old. At this site, the soil moisture (udic) and temperature (frigid) regimes favoured the formation of a thick and continuous carpet of gramineae. Yet, these conditions limited the activity of microorganisms and pedofauna, thus inducing a poorer horizon organisation. In this soil, because of the higher mean annual precipitation and root activity, most of the chemical modifications of the parent material occurred at the level of the rhizosphere, which acquired a thickness of 2–3 cm. From a chemical and mineralogical point of view, horizontal variations between rhizosphere and matrix were more evident than those among horizons. The most striking change occurring in the rhizosphere was the accumulation of secondary minerals such as oxalates and easily reducible Fe-oxyhydroxides. We also inferred that, in the environment of Mt. Etna, the excretion of oxalic acid from the roots of the broom could represent a strategy of nutrient uptake, in particular P, Mg and K.

The contrasting effect of broom and pine on pedogenic processes in volcanic soils (Mt. Etna, Italy)

Abstract Effects of Etnean broom ( Genista aetnensis (Biv.) DC.) and Corsican pine ( Pinus nigra Arn. ssp. laricio Maire) on the morphological, mineralogical and chemical properties of volcanic soils from Mt. Etna (Italy) were compared and contrasted. For this purpose, we studied the rhizosphere and the bulk soils under adjacent 30 years old pure plantations of both species. Morphology of the soil under broom differs from that under pine for (i) a higher accumulation of organic matter in the topsoil, (ii) an incipient formation of E material around the base of the stem, and (iii) the presence of yellowish collars around the primary roots. Mineral horizons of the two soils are made of plagioclases, pyroxenes, magnetite and glass. The yellowish colour of the collars is attributed to a root effect that results in a confined alteration of primary volcanic glass and also iron-bearing minerals, leading to the precipitation of amorphous Fe-oxides. Under pine, we observed a more widespread weathering of primary minerals throughout the profile, and a depletion of base cations and a release of Al in the topsoil. On the whole, therefore, Corsican pine—commonly planted in the last decades on the pyroclastic deposits and lava flows of the Etna volcano—seems to play a detrimental role on these soils.

Comparison of two soil organic matter extractants and determination of the “Walkley–Black” correction factors for organic fractions from a volcanic soil

Two extractants (0.1 M NaOH and a mixture 0.1 M NaOH–0.1 M Na4P2O7) were used separately to recover organic matter from a volcanic soil under Corsican pine (Pinus nigra Arn. ssp. laricio Maire). The presence of pyrophosphate did not considerably improve the recovery; on the contrary, in the topsoil, the aqueous NaOH was even slightly more efficient than the mixture. A comparison between dry combustion and dichromate oxidation (Walkley–Black method) to measure the organic carbon (C) in the extracted (fulvic and humic) fractions and in the soil residue was accomplished. Dichromate oxidation did not allow the detection of the entire (dry-burnt) C in the extracted fractions. The correction factor to account for undetected C varied according to horizon, organic fraction, and extractant. An apparent complete oxidation with the Walkley–Black method occurred for the soil residues, but it could be due to magnetite interference.

Randomly interstratified kaolinite-smectite from Galicia (NW Spain); a new procedure for determination

A new protocol was developed to examine an assemblage of kaolinite-smectite in a buried horizon of a paleosol developed on gabbro parent material. The new extraction procedure appears suitable for removing kaolinite and for ascertaining the nature of the smectite interstratified with kaolinite. Smectite was identified by X-ray diffraction (XRD) and infrared (IR) patterns, cation exchange capacity (CEC) and chemical analyses.The results obtained provide for increased understanding of the process of transformation of smectite into kaolinite.

Chemical and mineralogical changes in a polygenetic soil of Galicia, NW Spain

Abstract The soils of Galicia, NW Spain, developed on gabbro often include one or more buried profiles. In the modern overlying soil, gibbsite is common and the Fe oxyhydroxides include maghemite. In the buried soil interstratified kaolinite–smectite is abundant, gibbsite is present in traces and the Fe oxyhydroxides are mostly formed by goethite. Chemical and mineralogical data show that the modern soil has developed under strongly leaching conditions that contrast with those in which the buried soil formed. We suggest that the interstratified kaolinite–smectite is a relict mineral that helps reconstruction of the pedogenetic history of these soils.

Use of Waste Materials to Improve Soil Fertility and Increase Crop Quality and Quantity

1Dipartimento di Scienze Ambientali e delle Produzioni Vegetali, Universita Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy 2 Louisiana State University Agricultural Center, 307 M.B. Sturgis Hall, Baton Rouge, LA 70803, USA 3Departamento de Edafoloxia e Quimica Agŕicola, Escola Politecnica Superior, Universidad de Santiago de Compostela, Campus Universitario, Lugo, Spain 4Oficiul Pentru Studii Pedologice si Agrochimice Cluj, Street Fagului 1, Cluj-Napoca, Judetul Cluj, Romania