Extraction de l'adenosine triphosphate dans les sols: Une nouvelle methode de calcul des pertes en ATP

Adenosine triphosphate (ATP) was extracted from 6 soils and 3 ATP supplemented clays with a sulfuric acid reagent previously shown to minimize ATP losses. Results indicated that ATP losses were due to adsorption phenomena. The amount of adsorbed ATP was related to soil composition, soil weight and to the actual ATP content of the analysed soil sample. A mathematical formula was developed to determine the adsorption coefficient of ATP and consequently the ATP content of soils, using, for each soil, two experimentally determined soil ATP contents based on analysis using two different soil weights.The adsorption coefficient was constant in each soil, independent of soil ATP content and soil moisture content. Freeze-drying reduced the adsorption coefficient on 4 of the 6 soils but did not affect soil ATP content. In practice this method permits accurate correction for ATP losses, it simplifies the experimental procedure and reduces the number of analyses if multiple ATP measurements are required for a given soil under different conditions.     

Relations entre la fertilisation et la concentration des nitrates et du potassium dans les feuilles et le rendement et la qualite du mais de table

Abstract

Twenty sweet corn tissue samplings were made from ten field trials during 1974–76. Fertilization had little effect on yields, but a good relationship was found between yields and leaf tissue nitrate and potassium concentrations, in the leaves 40–50 percent developed at the F‐9, F‐13 and F‐14 vegetative stages. The lower and upper tissue nitrate and potassium concentration limits (deficiency and excess) were found to range between 2000 and 3000 ppm nitrate, and 1.5 and 4.2 percent, or 2.0 and 3.25 percent potassium, according to their vegetative development. Excessive nitrogen and phosphorus application decreased kernel tenderness and total solids (sugar) content, but potassium fertilization enhanced total sugar accumulation.     

Influence du niveau d'alimentation hydrique sur les variations du diametre des tiges,du potentiel hydrique,de la resistance stomatique,de la transpiration et de la photosynthese de l'aubergine (Solanum melangena L.)

The aim of this preliminary work was to test some biological criteria used for irrigation control. Microvariations of stem diameter, photosynthesis and plant growth were compared with previously recommended parameters such as leaf water potential and stomatal resistance, transpiration ...?Measurements were made on eggplants, grown in pots under a plastic greenhouse. Some of the pots were watered daily to compensate for transpiration losses. From Day J, watering was stopped for the “dry treatment” pots.As early as Day J + 2 stomatal resistances of both sides of the leaves were a little higher for the dry treatment than for the watered one. Net photosynthesis was only slightly reduced at the end of the afternoon.From Day J + 3, differences between the treatments increased for all the criteria: basic water potential, stomatal resistance, net photosynthesis. The stem diameter of the unwatered plants decreased and became smaller than for Day J + 2. All these results are coherent and indicate the interest of the stem diameter variation measurement as an irrigation control criterion. Compared with other criteria, it has the advantage of not needing any measurement on control plants, as water is the only acting factor.Moreover, for the watered plants, it has been pointed out that the stem diameter increase was linearly related to the cumulated net photosynthesis of the previous days. Such a relation would be an interesting criterion for greenhouse climate control.     

Caracterisation micromorphologique et hydrodynamique des niveaux structures par le gel Quaternaire dans les formations superficielles du bassin-versant de la Fecht (Vosges, France)

Detritic superficial formations, covering most of the slope in Fecht basin (Vosges, France), are deposited in the course of Quaternary cold periods. A detailed study on these deposits give evidence of structures directly or indirectly associated with the action of deep freezing and thawing: laminated structure, compact laminated structure with silt caps, stratified displaced granitic regolith, gelifluction deposits, etc. The cryogenic structures are generally well conserved, unless they are submitted to actual pedogenesis. Their influence on the hydrodynamic properties of the slope deposits is noteworthy: according to discriminant analysis, hydric comportment in this porous medium is largely influenced by the herited cryogenic structures. These structures, conserved under the actual soil, present high bulk density, weak water retention and low saturated hydraulic conductivity which are clearly contrasted to the values obtained in the upper part of the profile submitted to the destruction by pedogenesis. Particularly displaced granit regoliths, because of the included few permeable bands of fine material, react as a zone that hinders hydric transfers and induces lateral flows in slope deposits. This fact plays an important role in stationnal hydric budget.     

Etude integree de sols a pseudo-gley sous vegetation naturelle du plateau des Hautes Fagnes (Belgique): Partie III mesures du flux d''oxygene a l''aide de la microelectrode de platine dans les quatre stations

The author briefly reviews the principles of oxygen flux measurements and then describes the laboratory technique uses, the materials (soils) considered and the choice of effective tension. Current intensity is shown to vary with soil moisture. The author measures current fluctuations as a function of temperature, thus enabling calculation of activation energies. The author shows that the reduction current obtained could hardly be controlled by activation polarisation.     

Reduction de l'oxyde nitreux dans les sols de rizieres du senegal: Mesure de l'activite denitrifiante

A new method to estimate the rate of denitrification in soil was developed, and two different activities were measured: (1) the initial (or true) denitrifying activity of the soil under prevailing conditions; (2) the potential denitrifying activity induced by the addition of N₂O. Less than 50 g of soil, saturated with water, were incubated anaerobically at 37°C, with a known amount of N₂O, and the disappearance of N₂O was followed by gas chromatography. In 25 paddy soils of Senegal, a highly positive rank correlation was found to exist between the denitrifying activity measured by chromatographic and respirometric methods, under the same conditions of incubation with either N₂O or NO₃^? as the hydrogen acceptor. By the N₂O reduction method, it was found that there was no initial denitrifying activity in the rhizosphere of 3-week-old rice.     

Action des ions ferreux sur la reduction de l'acide nitreux dans les sols hydromorphes

It was postulated that chemical denitrification per se can take place in soils especially in the presence of certain metallic cations. Denitrification was measured by gas evolution from soil and changes in the proportion of different gases (N₂, N₂O and NO). Such measurements showed that in hydromorphous soils reduction of nitrite occurs in the presence of ferrous-iron. The influence of different extractant solutions and stirring of the soil during such experiments was investigated. In field soils N₂O and N₂ appear to be the only products of the reduction of NO₂^?-N by Fe²⁺.     

Transformations des carbonates dans une sequence de sols developpees sur marnes dans Le Bassin Aquitain,France

Soils of a toposequence formed chiefly in Tertiary marls in the south-eastern part of the “Bassin Aquitain” have been studied by field and micromorphological methods. Profiles were examined in detail in the field and oriented samples taken of horizons for observations of micromorphology. From the upper to the lower part of the toposequence, the four profiles also form a chronosequence, viz., a recent calcareous brown soil (sol brun calcaire), an old calcic brown soil (sol brun calcique), a still older leached brown soil (sol brun lessivé) and a hydromorphic leached soil (sol lessivé hydromorphe).The profile distribution and forms of calcite can be related to the morphology, ages and parent materials of the soils. Calcite is found as relics in the upper horizons of the calcareous brown soil and in the form of accumulations in the Bca and Cca horizons of the calcareous brown soil, the calcic brown soil and the leached brown soil. Where accumulations are limited, calcite forms pseudomycelia associated with roots, first as calcitans in tabular pores or craze planes and second as coalescing pseudomycelia. Finally, the calcite invades the S-matrix by epigenesis and results in crumbly masses. These masses have the shapes of the structural voids originally present in the parent materials. The common voids in the marl are vertical craze planes, the widths of which differ with the moisture regime of a soil. In the sandstones, the craze planes are horizontal and very small. The distribution of the calcitans and the presence of the crumbly masses indicate that the processes of accumulation of calcite are in part biodependent, i.e., related to root distribution, and in part lithodependent, i.e., related to structure of the parent rock.Finally, the presence in the calcareous brown soil of calcite as relics in the upper horizons and as successions of cutans from outsides to insides of pores (calcitan, argillan, calcitan) in the Bca horizon shows that the profile has a polycyclic origin.     

Influence de la roche-mère et du climat sur les propriétés andiques des sols en région montagnarde tempérée (Vosges, France)

La diversité des conditions d’environnement (roche-mère, climat, végétation) prévalant dans un massif de moyenne montagne (Vosges, France) nous a permis d’établir leur rôle dans la manifestation à des degrés divers des propriétés andiques dans le sol. Nous avons examiné un lot de 13 profils sélectionnés à partir de critères lithologiques, climatiques et morphologiques présumés favorables à l’expression de ces propriétés andiques: roches-mères basiques d’origine volcanique ou non, climat montagnard très humide, abondance de matière organique sur une grande profondeur. Ces profils se subdivisent en deux populations. Quatre d’entre eux peuvent être classés comme des Andisols (Alic Fulvudands) alors que les autres ont des propriétés andiques trop faiblement exprimées pour appartenir à cet ordre et doivent être classés comme des Andic Haplumbrepts. Tous ces sols sont dépourvus d’allophanes. Dans cet environnement de moyenne montagne, les facteurs favorables à la manifestation de propriétés andiques sont d’une part, les altitudes et les expositions qui induisent de faibles températures et de fortes précipitations et d’autre part, l’altérabilité des roches-mères déterminée par leur composition chimique et minéralogique. Comme les vieux matériaux volcaniques sur lesquels se développent la plupart des sols étudiés sont pauvres en verres, voire complètement dévitrifiés, les Andisols vosgiens présentent beaucoup d’analogies avec les Andisols non-allophaniques non-volcaniques identifiés dans d’autres environnements. Leurs propriétés andiques sont faiblement exprimées et elles sont dues à la présence de complexes organo-métalliques associée à des teneurs élevées en carbone organique. The diverse environmental conditions (parent material, climate, vegetation) in the Vosges Mountains (France) allow us to investigate their role in the development of soils with varying degrees of andic properties. We studied 13 profiles selected on the basis of lithological, ecological and morphological criteria assumed to favour the formation of andic properties, i.e. basic parent materials of volcanic and other origins, wet montane climates and accumulation of thick layers of organic matter. The profiles belong to two classes: four are Andisols, more precisely Alic Fulvudands, and the others are Andic Haplumbrepts with only weakly expressed andic properties. In this montane environment the factors favouring the andic properties seem to be on the one hand height and exposure inducing cold and humid microclimates, and on the other the chemical and mineralogical composition controlling the weatherability of the soil’s parent materials. For example, the old volcanic rocks on which most of the soils occur are poor in glassy material or are even completely devitrified. Accordingly, Andisols in the Vosges are like those of non-volcanic, non-allophanic Andisols elsewhere in the world: their andic properties are weakly expressed and are caused by organo-metallic complexes associated with their upper organic-rich horizons rather than by allophanes.     

Etude integree de sols a pseudo-gley sous vegetation naturelle du plateau des Hautes Fagnes (Belgique): Partie I le milieu de pedogenese, la morphologie et le fonctionnement actuel des profils

This work is an attempt to establish the morphogenesis of four hydromorphic profiles (Plateau des Fagnes, Eastern part of the Belgian Ardennes). Various scientifical approaches were used, namely geomorphology, mineralogy and palynology.The aim was to show that very sharp discordances may appear between “inherited” profile morphology and the present state of hydromorphy characterized by vegetation, humus forms, and physico-chemical measurements, such as redox potential and oxygen diffusion flux intensity (see partie II)