Micromorphology of periglacial sediments from the Tayara site,Qikirtaq Island,Nunavik (Canada)

Soil micromorphology provides an excellent resource for investigating Palaeoeskimo site-formation processes in the low arctic periglacial environment. In this study, micromorphology was used to answer questions concerning the composition, structure, origin and depositional agencies of the Tayara site active layer's sediments as well as to distinguish between natural (geogenic, biopedogenic) and cultural (anthropogenic) processes. Five groups of microfeatures were documented. These include 1) biopedological features (soil organic matter accumulation, mesofaunal and fungal activities), 2) transport-inherited features related to depositional processes (solifluction and stream sedimentation), 3) frost-induced microstructures and cryogenic features such as major post-depositional changes (ice-segregation, particle rearrangement, frost shattering, cryoturbation), 4) bone preservation in the active layer at the microscopic level, and 5) anthropogenic features related to Palaeoeskimo activities. The sediments from the three archaeological levels (I, IA and II) appear to have been very little influenced by anthropogenic factors. Cultural processes are micromorphologically observed in level II, with some evidence of feeding (bone presence), burning (wood charcoal, heated bone), and possibly trampling. However, the effects of natural processes on the sediments are more pronounced than anthropogenic ones.     

Channel incision, gravel mining and bedload transport in the Rhône river upstream of Lyon, France (“canal de Miribel”)

The Miribel canal is a former arm of the Rhône embanked between 1848 and 1857 over a length of 18 km to improve navigation at low discharges. The impact of this was a hydraulic tilting of the long profile characterised by 4 m of degradation upstream and 4-6 m of aggradation of bedload downstream. This phenomenon increased downstream flooding. Since 1937 a diversion dam has controlled upstream water input, thus reducing the transit of the pebble bedload. However, excessive harvesting of sands and gravels occurred between 1970 and 1980, resulting in a general lowering of the river bed and the accompanying water table with ecological consequences in the alluvial plain and for water supply. This development made it all the more necessary to obtain knowledge about the bedload discharges passing through the Miribel canal, and more broadly about the hydraulic conditions as functions of the varying discharge. Calculation of shear stresses and grain size measurements on the lateral bars after several floods in 1989-90 show that movement of bed-material is initiated at a discharge of 440 m³ · s⁻¹ (equalled or exceeded 40 days · year⁻¹), and becomes general at 550 m³ · s⁻¹ (equalled or exceeded 30 days · year⁻¹). Transport discharge is thus relatively frequent and involves distal fluvio-glacial deposits composed of fine-grained materials. Potential transport calculated by the Meyer-Peter formula is around 60,000 t · year⁻¹ for the range of discharges between 440 and 850 m³ · s⁻¹. For these discharge values, the canal experiences a loss of materials without replacement from upstream; for higher rates of discharge, the floodgates let through an unknown quantity of materials which partially make up the loss. Gravel harvesting ceased in 1991 but the diversion dam will have to be operated in a different way in order to increase the input of bedload into the canal.     

Communication of the results of the “Primary Production in the Sahel (PPS)” research project

The main conclusions of the Malian-Dutch “Primary Production in the Sahel (PPS)” research project, which was carried out during 1976–1981 (Penning de Vries and Djitèye, 1982), may be summarized as follows: (1) poor soil quality is just as great a barrier to rural development as water shortage; (2) animal production is high per unit area, compared with similar ecological zones in the U.S.A. and Australia; (3) attempts to increase production without due attention to the shortage of soil nutrients are bound to fail; (4) socio-economic conditions determine the feasibility of productive investments in agriculture in the Sahel. This article presents the PPS approach to publicizing these results and promoting a badly needed revision of development policy in the Sahel.     

Note on the genesis and ecology of “White Pulp Soils” in NE- China

“White Pulp Soils” are eutric Planosols, their permeability profile being caused more by stratification than by lessivage and most likely not by ferrolysis. For climatic reasons their water/air regime differs very much from many other surface water soils, dry periods being more typical for the early and wet ones for the late summer. This may influence the diagnostic weight of the profile morphology and the transferability of ecological threshold values from stagnosols of other regions.     

“Take only photographs and leave only footprints”?: An experimental study of the impacts of underwater photographers on coral reef dive sites

Impacts caused by recreational scuba diving on coral reefs vary widely among different dive locations and individual divers. Linear modelling was used to explore a range of individual and situational risk factors associated with divers who damaged corals in the Great Barrier Reef Marine Park. Recreational divers were followed for 10–15 min, and all contacts with, and damage to corals were recorded. Information on the dive site, diving experience, gender, and use of an underwater camera were recorded. Thirty-two out of 214 divers (15%) damaged or broke corals, mostly by fin kicks (95%). Impacts were most likely to be caused by male divers, in the first 10 min of the dive, at sites with a large abundance of branching corals. Specialist underwater photographers caused more damage on average (1.6 breaks per 10 min) than divers without cameras (0.3 breaks per 10 min). To explore the effects of gender and use of a camera further, we issued single-use underwater cameras to 31 randomly chosen divers and compared their behaviour to a control group. Use of a camera had no influence on the rate or amount of damage caused by these naïve photographers, but male divers were more likely to break corals and caused significantly more damage, on average, (1.4 breaks per 15 min) than female divers (0.3 breaks per 15 min). Variability in the amount of damage caused by divers in our sample reflected the very different underwater behaviours exhibited by specialist and non-specialist photographers, and male and female divers. Greater understanding of the causes of harmful behaviours by these groups will allow better targeting of on-site interpretative and cautionary information and may prove to be a more palatable management strategy than regulation of site use.     

The role of “effective microorganisms” in the composting of banana (Musa ssp.) residues

“Effective microorganisms” (EM) are a poorly defined mixture of supposedly beneficial microorganisms that are claimed to enhance microbial turnover in compost and soil. In Costa Rica, EM are used to produce organic compost (bokashi) from banana residues (Musa ssp.). Given the scarcity of scientific data about the effects of EM on the mineralization of plant residues, this study aimed at investigating the effects of EM addition on the decomposition of banana residues during Bokashi production. To this end, the following non‐EM treatments were compared to EM Bokashi: Bokashi produced with water (W), with molasses (M) as an EM additive, and with sterilized EM (EMst). Subsequently, the effects of the resulting Bokashi treatments on the growth of young banana plants were evaluated. Compared with non‐EM controls, the effect of EM on the mineralization of banana material was negligible. Dry‐matter losses of the composts with different EM treatments were similar, with about 78% over 5 weeks. Ergosterol concentration was highest in EM Bokashi (77 µg (g dry soil)^–1) and lowest in EMst Bokashi (29 µg (g dry soil)^–1). Microbial biomass carbon (C_mic) and microbial biomass nitrogen (N_mic) were both lowest in EM (C_mic = 3121 µg g^–1; N_mic = 449 µg g^–1), while C_mic was highest in Bokashi produced with molasses (3892 µg g^–1) and N_mic was highest in EMst (615 µg g^–1). Treatment effects on adenylate concentrations and adenylate energy charge were negligible. Application of all Bokashi variants to young banana plants significantly increased shoot growth under greenhouse conditions compared to plants grown in a control soil without amendments. However, these effects were similar for all Bokashi treatments, even if EM Bokashi increased the K concentrations in banana leaves significantly compared to Bokashi produced with EMst and the control. Bokashi produced with only molasses and EM Bokashi decreased the number of root nematodes under greenhouse conditions compared to the control. Overall, the results confirmed the expected influence of composting on the degradation of organic material and the effect of compost application on plant growth. Hower, under the conditions of this study, EM showed no special effects in this, except for increasing the K concentrations in the leaves of young banana plants.     

Submicroscopic characterisation of phosphatic and sesquioxidic nodules of some soils of the “Chaco deprimido” (Argentina): Preliminary results

In this paper two examples are presented of the investigation by submicroscopic techniques, of particular problems in the characterisation and analysis of various pedological features in soils of the “Chaco Deprimido”.

The first concerns nodules seen in an alluvial soil. The techniques established their phosphatic composition and identified them as small bone fragments which are undergoing alteration.

The second relates to study of sesquioxidic nodules and cutans in solodised soils and planosols, and shows them to have a dominantly manganiferous composition; this result enables one to make certain interpretations concerning the physicochemical conditions essential for the formation of such pedological features.     

Adsorption of “real” dissolved organic matter on the clay and fine silt fractions of a forested Stagnic Gleysol

Dissolved organic matter (DOM) in soils is partially adsorbed when passing through a soil profile. In most adsorption studies, water soluble organic matter extracted by water or dilute salt solutions is used instead of real DOM gained in situ by lysimeters or ceramic suction cups. We investigated the adsorption of DOM gained in situ from three compartments (forest floor leachate and soil solution from 20 cm (Bg horizon) and 60 cm depth (2Bg horizon)) on the corresponding clay and fine silt fractions (< 6.3 μm, separated together from the bulk soil) of the horizons Ah, Bg, and 2Bg of a forested Stagnic Gleysol by batch experiments. An aliquot of each clay and fine silt fraction was treated with H₂O₂ to destroy soil organic matter. Before and after the experiments, the solutions were characterized by ultra‐violet and fluorescence spectroscopy and analyzed for sulfate, chloride, nitrate, and fluoride. The highest affinity for DOM was found for the Ah samples, and the affinity decreased in the sequence Ah > Bg > 2Bg. Dissolved organic matter in the 2Bg horizon can be regarded as slightly reactive, because adsorption was low. Desorption of DOM from the subsoil samples was reflected more realistically with a non‐linear regression approach than with initial mass isotherms. The results show that the extent of DOM adsorption especially in subsoils is controlled by the composition and by the origin of the DOM used as adsorptive rather than by the mineralogical composition of the soil or by contents of soil organic matter. We recommend to use DOM gained in situ when investigating the fate of DOM in subsoils.     

Erratum to “Soybean yield as affected by crop rotations, deep tillage and irrigation layout on a hardsetting Alfisol”: [Soil & Tillage Research 44 (1997) 151–164]

The hardsetting surface of many Alfisols in Australia is a limiting factor in crop production. Better soil management systems are required to improve productivity. This study reports the effects of several untested management systems, involving the combined effects of tillage (deep ripping, deep mouldboard ploughing and disc ploughing), irrigation layout (permanent beds, border ditch) and crop rotation treatments (single cropping, double cropping and pasture), on soil structure and the production of irrigated soybeans [Glycine max (L) Merr.] on a hardsetting Alfisol. It was conducted under a system of controlled traffic near Trangie, NSW, Australia. The double cropping and pasture treatments increased total water entry, soil organic carbon and soybean leaf water potential. Consequently, soybean yield was increased by as much as 58%. The retention of cereal and pasture stubble increased total water entry by slowing the rate of irrigation water advance, reducing the potential for slaking and increasing the number of continuous vertical macropores. The increases in soil water were associated with a reduction in soil strength; a key limiting factor in crop growth on hardsetting Alfisols. Deep tillage or the use of permanent beds did not affect soybean yields under the conditions reported in this paper, although the combination of disc ploughing and furrow irrigation was successful.     

Use of GIS and remote sensing for soil mapping and for locating new sites for permanent cropland — A case study in the “highlands” of northern Thailand

Until a few decades ago, the highlands of northern Thailand were predominantly under forest. Since then, a growing pressure on the land, partly from hill tribes living in the highlands, has led to rapid deforestation and land degradation. To counteract these problems, the Royal Thai Government started a “Highland Development Project” in 1990. Activities of this project include soil inventories and the use of soil and other data to locate new sites for cropland and settlements for hill tribes. In this paper, a case study is described in which the use of a Geographic Information System (GIS) and digital remote sensing methods is compared with the methods currently used in these activities. The GIS is used for the preparation of a terrain mapping unit (TMU) map which integrates data from existing maps and data interpreted from satellite images. The GIS is also used (i) to derive relevant information from the TMU/soil map (e.g. land suitability and estimated erosion rates) and (ii) to integrate this information with land cover/use and accessibility information. This integrated information is used to locate physically suitable, accessible and not yet used areas that could become potential new cropland sites for highland people after resettlement.

A comparison between the currently used methods and the GIS methods shows that apart from considerable time savings, also improvements in data quality are achieved, e.g. by the preparation of a slope map based on a digital terrain model and by up-dating of existing land use information with satellite imagery. The spatial and attribute data base in the GIS makes it possible to use the original, non-aggregated data and, in addition, facilitates the integration of the various data for the analysis of potential sites for resettlement according to various criteria and objectives.     

”The principles of rational agriculture” by Albrecht Daniel Thaer (1752–1828). An approach to the sustainability of cropping systems at the beginning of the 19th century

The identification of quantitative fertility indicators for evaluating the sustainability of cropping and farming systems has become a major issue. This question has been extensively studied by the German agronomist Albrecht Daniel Thaer at the beginning of the 19^h century. In this paper Thaer's work is set in its historical background, from the end of the 16^th century (Palissy, 1580) to the middle of the 19^th century (Liebig, 1840). Then the paper focuses on Thaer's quantitative and complex fertility scale (expressed in “fertility degrees”), which was based on soil properties, on the requirement of nutrients by plants, and on the cropping system (including crop rotation). Thaer expressed soil fertility and economic results as a function of rye production in “scheffel of rye per journal” (ca. 200 kg per hectare). He also proposed a scale to describe the intrinsic fertility of soil. Thaer used this approach to assess the effect of major German cropping systems on soil fertility. He applied it to eight theoretical systems and nine existing systems in a true modeling approach. Thaer completed the fertility evaluation for the nine existing systems with a detailed economical analysis commenting the limits and potentialities of each system. Thaer's approach was used with success during half a century as it combined numerous empirical findings on soils and fertilization with organic substances in a sophisticated model. Unfortunately and despite effective practical applications, the scientific foundations of Thaer's “Humus Theory” proved definitively false as soon as 1840 when Sprengel and Liebig published on mineral nutrition of plants. Thaer's work deserves to be rediscovered since it approaches the modern issue of the sustainability of cropping and farming systems.     

Pedobiochemical indicators for eutrophication and the development of ”︁black spots” in tidal flat soils on the North Sea coast

The increasing eutrophication of tidal flat soils on the North Sea coast and the appearance of ”︁black spots” gave rise to this study. The aim was to find pedobiochemical indicators for the development of ”︁black spots”. Artificially eutrophicated soils were compared with untreated soils in the field and laboratory. The pH values of the artificially eutrophicated and natural soils often differed by nearly one unit. The treated soils mostly showed lower redox potentials (˜ —300 mV) than the untreated samples (˜ —250 mV). The mean sulfate concentrations were 2.2 mM in the eutrophicated laboratory soils and 13.1 mM in the eutrophicated field soils, compared with 12.5 mM and 20.2 mM in the untreated ones. Consequently, the SO₄^2—:Cl^— ratios and SO₄^2— differences were lower in the treated soils. Non‐eutrophicated soils showed methane concentrations of < 5 nmol cm^—3, whereas the eutrophicated soils showed up to 217.0 nmol cm^—3 in the field and 479.1 nmol cm^—3 in the laboratory. Differences between field and laboratory data were mainly due to a continuous sulfate supply and reoxidation process only possible in the field. Although all parameters showed differences between the eutrophicated and untreated soils, only the methane data did not overlap with their interquartile ranges. Those of the untreated soils were 2—7 nmol cm^—3 and those of the treated were 12—360 nmol cm^—3. Thus, threshold values can be defined. Methane concentrations of approximately > 10 nmol cm^—3 refer to the beginning eutrophication process and those in the range of > 100 nmol cm^—3 to advanced processes, phenologically forming ”︁black spots”.