De Enkeerdgrond: de meest kenmerkende bodem van Nederland

De Nederlandse Bodemkundige Vereniging hield dit jaar in het kader van haar 75-jarig jubileum een verkiezing binnen haar ledenbestand voor de meest kenmerkende bodem van Nederland. De enkeerdgrond eindigde daarbij met 25% van de stemmen op de eerste plaats. Tweede en derde werden respectievelijk de koopveengrond en de poldervaaggrond

Aspects of mineral transformation during weathering of volcanic materials : the microscopic and submicroscopic level

Mineral transformation at the earth surface is a complex process. In volcanic ejecta, such transformations tend to be fairly rapid. Many weathering studies on volcanic materials have been carried out at different scales of observations, mostly using bulk samples. However, to get a proper understanding of the mechanisms of weathering of primary minerals and formation secondary minerals it is necessary to obtain data of undisturbed material at the scale of observation that micromorphology and submicroscopy deal with. Weathering studies at the micrometre scale with help of micromorphology showed the heterogenous character of mineral weathering and the co- existence of different secondary minerals.The main objective of papers in this thesis was to characterize and explain alteration of primary minerals and formation of secondary minerals at the particle level in volcanic soils in relation to (micro) environmental conditions.Thin sections of volcanic soils were studied by micromorphology, and relevant features were characterized chemically and mineralogically by submicroscopical methods performed on (un)disturbed samples isolated from thin sections.Mineral transformations were studied both on sites in the temperate humid zone and in the humid tropics.In a chronosequence of Quaternary terraces of the Allier in France, micromorphological and sub microscopical analyses showed:- Alteration of basaltic particles leads to clay formation whereas weathering of granite fragments contributes to the sand fractions.- A relative increase in the contents of Ti, Al, and Fe and a decrease of K, Na, Ca, and Si occur in weathering rinds of basalt pebbles. Differences in weathering intensity are predominantly a function of chemical composition of the basalt rather than a function of time.- A mass balance calculation carried out on an isovolumetric, altered basalt pebble with a fresh core, and on an enclosed, genetically related neoformed clay coating showed that all elements, except Fe were leached from all weathering rinds. Only Si, Al and some Ca were found in the clay coating, and part of the Al was derived from an external source.- Isotropic and anisotropic coatings occur in a Paleosol in an older terrace. Micromorphological observations demonstrated that such coatings are genetically related. The isotropic coating consists of allophanic material with minor amounts of 2:1 phyllosilicates, whereas the anisotropic types consist of 2:1 phyllosilicates only. Both types result from recombination of trachytic weathering products under restricted leaching conditions during coating formation.- Micromorphological observation demonstrated three types of coatings in two Planosols in two older terraces. Isotropic and anisotropic, translucent materials occur locally within one coating, suggesting a genetic similarity. These coatings are due to secondary mineral formation, The third type, anisotropic dusty clay coatings clearly resulted from clay illuviation. Cluster analyses reveal that the coatings of the same type were chemically more alike than different coatings in the same profile. About 83% of the grouped samples were classified correctly as either isotropic and anisotropic weathering coatings or anisotropic illuviation coatings.A technique is described to isolate undisturbed microparts of pedofeatures from thin sections. Such microparts can subsequently be analysed by Transmission Electron Microscopy. This technique allows performance of micromorphological, mineralogical and chemical analyses on one undisturbed micro sample at micrometre to nanometre scales.Isotropic coatings in the C horizon of a young Hapludand in Guadeloupe and in the C and R horizons of an old Hapludand in Costa Rica, both developed on andesitic volcanic materials were allophanic. Isotropic coatings present in the Bw horizons of both soils contain allophane and imogolite. The Al/Si molar ratios in the coatings in the Bw horizons are higher than those in the coatings of the C and R horizons. Anisotropic coatings are wholly gibbsitic and occur only in the Bw horizon of the older Costa Rican Hapludand. The gibbsitic coatings show a gradual transition to isotropic coatings and both types looks alike in plane polarized light suggesting a genetic relationship. The allophane coatings resulted from initial weathering of the parent materials, whereas the gibbsite coatings represent the ultimate stage of secondary mineral formation. The differences in chemical and mineralogical composition of the coatings are thought to be the result of different leaching conditions at the macro and micro scale.2:1 Phyllosilicates in Hapludands on Holocene andesitic beach ridges in Costa Rica occur as clay pseudomorphs after primary minerals. They are inherited from hydrothermally altered parent material from which the beach ridges were derived, and are not due to post depositional soil formation. Weathering and biological activity affect the clay pseudomorphs which leads to clay- sized particles consisting of 2:1 phyllosilicates. They are incorporated in the allophanic groundmass that results from actual soil formation in the Hapludands.Isotropic coatings also found in a West Java (Indonesia) Oxisol on andesitic volcanic parent materials are probably due to weathering of airborne ash additions. The coatings recrystallize to anisotropic coatings suggesting a neoformed genesis. Both types of coatings appear to be common in three andesitic catenas in Indonesia. The amount of coatings and the crystallinity tend to increase as the dry season become more pronounced. The anisotropic coatings can easily be confused with illuviation coatings

Fossil and recent soil formation in Late Pleistocene sand deposits in the eastern part of the Netherlands.

Along the Slinge Brook near Winterswijk, a profile was investigated which is assumed to consist of two aeolian deposits: Old Coversand I at the bottom and Old Coversand II at the top, between which a fluvioglacial deposit occurs, the Beuningen Complex. The profile, which now is well-drained, was poorly drained from the beginning of the Holocene up to some centuries ago. The following soil forming processes were recognized micromorphologically: decarbonation, biological activity, clay illuviation, decomposition of illuviated clay and one or two cycles of gleying. It was concluded that: (1) during the deposition of the Beuningen Complex a hydromorphic cycle may have occurred in this profile; (2) between the beginning of the Bolling interstadial and the rise of the watertable at the beginning of the Holocene, biological activity and clay illuviation occurred and possibly some decarbonation; (3) between the beginning of the Holocene and recent times a hydromorphic cycle (possibly the second) took place; (4) finally in recent times biological activity and decarbonation occur. (Abstract retrieved from CAB Abstracts by CABI’s permission

The morphology and genesis of pseudogley phenomena in a Pleistocene loamy sand in the Netherlands.

[183.64:141.791]In a loamy sand profile with deep watertable, developed in Pleistocene deposits and showing mottling patterns and fine-textured bands and tongues, four soil-forming processes were recognizable: illuviation of fine clay and iron oxides, biological activity, pseudogleying, and breakdown of the clay fraction at the upper side of the illuviation horizon. The genesis of this soil can be explained by assuming that soil formation started where frost wedges occurred in the profile during the late Pleistocene and proceeded further at these points than in other parts of the soil. (Abstract retrieved from CAB Abstracts by CABI’s permission

Fossil and recent soil formation in lateleistocene loess deposits in the southern part of the Netherlands.

In the younger, Weichselian (Wurm, Wisconsin) loess deposits in the south of the Netherlands there is a horizon with fossil pedotubules (filled animal burrows). These pedotubules, 3 mm ( plus or minus 1 mm) in diameter, unbranched, without preferential orientation, are most abundant in the zone extending from about 30 cm above the decalcification boundary (situated 2-3 m below the soil surface) to some decimeters below it. They are rare in the B3t horizon of the overlying Hapludalf. Their lower extension boundary occurs some 2 m below the decalcification boundary. These tubules result from fossil animal activity followed by decalcification, mainly of a Boelling soil surface. A loess layer some 2 m thick was probably deposited in the post-Boelling period; the lower part of this layer has a lamellae spot zone. Micromorphological evidence shows that the lamellae spot zone was originally at the actual soil surface. Consequently a geogenic origin of the lamellae spot zone rather than a pedogenic origin seems likely. Soil formation subsequently intensified the textural differences. It is suggested that the post-Boelling loess was free of calcium carbonate at the beginning of the Holocene and was deposited non-calcareously or was decalcified synsedimentarily. In Western Europe, loess soils formed from Pleistocene deposits probably matured earlier in the Holocene than has been assumed hitherto. (Abstract retrieved from CAB Abstracts by CABI’s permission

The mineralogical composition of calcium and calcium-magnesium carbonate pedofeatures of calcareous soils in the European prairie ecodivision in Hungary

Abstract There is little data on the mineralogy of carbonate pedofeatures in the calcareous soils in Hungary which belong to the European prairie ecodivision. The aim of the present study is to enrich these data. The mineralogical composition of the carbonate pedofeatures from characteristic profiles of the calcareous soils in Hungary was studied by X-ray diffractometry, thermal analysis, SEM combined with microanalysis, and stable isotope determination. Regarding carbonate minerals only aragonite, calcite (+ magnesian calcite) and dolomite (+proto-dolomite) were identified in carbonate grains, skeletons and pedofeatures. The values relating, respectively, to stable isotope compositions (C13, O18) of carbonates in chernozems and in salt-affected soils were in the same range as those for recent soils (latter data reported earlier). There were no considerable differences between the values for the carbonate nodules and tubules from the same horizons, nor were there significant variations between the values of the same pedofeatures from different horizons (BC-C) of the same profile. Thus it can be assumed that there were no considerable changes in conditions of formation. Tendencies were recognized in the changes of (i) carbonate mineral associations, (ii) the MgCO3 content of calcites, (iii) the corrected decomposition temperatures, and (iv) the activation energies of carbonate thermal decompositions among the various substance-regimes of soils. Differences were found in substance-regimes types of soils rather than in soil types

Rauch Axis: degelijkheid en eenvoud

De Axis is het nieuwste model kunstmeststrooier van Rauch. Deze strooiers zijn nu enkele seizoenen in gebruik. Door gebruikers worden de machines ervaren als degelijk en eenvoudig in gebrui

Rauch Axis: degelijkheid en eenvoud

De Axis is het nieuwste model kunstmeststrooier van Rauch. Deze strooiers zijn nu enkele seizoenen in gebruik. Door gebruikers worden de machines ervaren als degelijk en eenvoudig in gebrui