ALBERT

Notes: The Susunai Complex of southeast Sakhalin represents a subduction-related accretionary complex of pelitic and basic rocks. Two stages of metamorphism are recognized: (1) a local, low-P/T event characterized by Si-poor calcic amphiboles; (2) a regional, high-P/T event characterized by pumpellyite, actinolite, epidote, sodic amphibole, sodic pyroxene, stilpnomelane and aragonite. The major mineral assemblages of the high-P/T Susunai metabasites contain pumpellyite + epidote + actinolite + chlorite, epidote + actinolite + chlorite, epidote + Na-amphibole + Na-pyroxene + chlorite-(-haematite. The Na-amphibole is commonly magnesioriebeckite. The Na-pyroxene is jadeite-poor aegirine to aegirine-augite. Application of empirically and experimentally based thermobarometers suggests peak conditions of T= 250–300C, P= 4.7–6 kbar. Textural relationships in Susunai metabasite samples and a petrogenetic grid calculated for the Fe3+-rich basaltic system suggest that pressure and temperature increased during prograde metamorphism.

Notes: In the Llano Uplift of central Texas (USA), prograde homogenization of garnet growth zoning took place during moderate-to high-pressure dynamothermal metamorphism over a narrow temperature range near the transition from the amphibolite to the granulite facies. This subtle record of early dynamothermal metamorphism survived subsequent static metamorphism at low pressures in the middle-amphibolite facies, despite the destruction of most high-pressure mineral assemblages that originated in the early metamorphic episode. Geographically systematic variations in the degree of homogenization indicate that the uplift as a whole underwent high-pressure metamorphism, in accord with emerging tectonic models for the mid-Proterozoic evolution of the southern margin of the North American continent.

Notes: In north-central Wopmay Orogen, syntectonic low-P(Buchan-type) suites of mineral isograds outline regional metamorphic temperature culminations that are associated, at the higher structural levels, with emplacement of early Proterozoic plutons in the west part of a deformed and eastward transported continental margin prism. The mapped isograds mark the first occurrence of biotite, staurolite, andalusite, sillimanite, sillimanite-K feldspar and K feldspar-plagioclase-quartz ± muscovite (granitic) pods in metapelites, with increasing proximity to the plutons.Microprobe analyses and field observations have resulted in the formulation of reactions for the ‘ideal’pelitic system K2O-Na2O-FeO-MgO-Al2O3-SiO2-H2O-Al2O3-SiO2-H2O, to account for the various mineral assemblages of each metamorphic zone. A P-T petrogenetic grid showing erosion surface P-T curves for the northern Wopmay Orogen pelites, compiled on the basis of the mapped isograds and the inferred reaction(s) for each metamorphic zone, documents a variation in exposed metamorphic pressure ranging between 2 and 4 kbar.The configuration of a new bathograd, based on the invariant model reaction sillimanite + K feldspar + plagioclase + biotite + quartz + vapor ± muscovite + liquid and interpolated across three metamorphic suites, is consistent with a major regional structure culmination and with independently determined pressures obtained from anorthite-grossular-quartz-Al2SiO5 geobarometry. The positive correlation between the configuration of the bathograd and the structural and pressure culmination points to the pressure-dependence of anatectic-granitic-pod mineral associations.

Notes: Variations in assemblage and composition of the constituent minerals in basic and intermediate metavolcanics encountered in the Zarouchla Group of the Phyllite-Quartzite Series are consistent with a progressive sequence, corresponding to temperature conditions estimated at 290-380°C (minimum values) under a total pressure greater than 3°5kbar and possibly as high as 5 kbar. In the absence of more critical evidence, the parageneses recorded in the metavolcanic rocks are interpreted as belonging to a prograde facies series from the lawsonite-albitechlorite facies through the pumpellyite-actinolite facies to the greenschist facies. The present distribution of mineral assemblages does not show a simple increase of metamorphic grade in a given direction but is apparently related to the tectonic evolution of the metamorphic sequence.

Notes: Abstract Mylonites from shear zones cutting Hercynian gneisses in the central Pyrenees have been studied in thin section and using the electron microprobe. The shear zones contain retrogressive greenschist facies assemblages implying introduction of an aqueous fluid during deformation in the zones. Textural evidence suggests that fluid-rock interaction occurred throughout the active life of the shear zones.Whole-rock chemical changes during deformation are documented in a variety of mylonitic lithologies and retrogressed country rocks. The overall effect was to reduce chemical differences between lithologies. Activity diagrams show that this would be expected if a hydrous fluid was circulating between different lithologies during deformation. In most cases fluid/rock ratios were relatively small resulting in gradual chemical changes and repeated recrystallization. ‘Open-system’behaviour with reduction in the number of phases is seen in some granite mylonites, suggesting focusing of fluid movement in parts of the shear zones. Continual fluid-rock interaction may have led to reaction-enhanced ductility in the shear zones over a long period of time. The source of fluid is uncertain, but may be related to underthrusting of material beneath the area investigated.

Notes: Abstract The hornblende-bearing basic gneisses in the Uvete area, central Kenya, were metamorphosed under a narrow range of P and T (6.5 ± 0.5kbar and 530 ± 40°C) of the staurolitekyanite zone in the Mozambique metamorphic belt. They show a wide variety of divariant and trivariant mineral assemblages consisting of hornblende, cumminatonite, gedrite, anthophyllite, chlorite, garnet, epidote, clinopyroxene, plagio-clase and quartz. The bulk and mineral chemistries and the graphical representation of phase relations show that each mineral assemblage approaches chemical equilibrium and defines a unique composition volume in the A′(Al + Fe3+− (13/7)Na)-F(Fe2+)-M′(Mg)-C′(Ca-(3/7)Na) tetrahedron. The composition volumes are distributed quite regularly and do not overlap each other.The phase relations in the Uvete area are in contrast with those in the staurolite-kyanite zone amphibolites in the Mt. Cube quadrangle, Vermont. The amphibolites there contain low-variance mineral assemblages formed under different values of μH2O and μCO2. These assemblages define overlapping composition volumes in the A′-F′-M′-C’tetrahedron.The mineral assemblages in the Uvete area are interpreted as having formed in equilibrium with fluid at a high and nearly constant μH2O value. Such a fluid composition was externally controlled by the supply of H2O-rich fluid expelled from the surrounding pelitic and psammitic rocks. The body size of the basic gneisses in the Uvete area (less than 400m in thickness) was small enough for the fluid to migrate completely.

Notes: Abstract Blueschist-facies rocks on the Seward Peninsula constitute a structurally coherent terrane measuring at least 100 × 150 km. Radiometric age data indicate that high-pressure metamorphism probably occurred in Jurassic rather than in Palaeozoic or Precambrian time, as previously suggested. Protolith sediments (Nome Group) are of intracontinental basin or continental margin type, and of lower Palaeozoic and possibly late Precambrian age, thus predating the high pressure metamorphism by more than 200 m.y.Blueschist-facies mineral assemblages were developed in almost all lithologies of the Nome Group, and are best preserved in FeTi-rich metabasites (glaucophane + almandine + epidote) and pelites (glaucophane + chloritoid + phengite). A lawsonite–crossite subfacies was developed in possible Nome Group rocks on the east flank of the Darby Mountains. Albite–epidote–amphibolite facies assemblages characterize Nome Group rocks in the southwestern part of the Peninsula. Metamorphism in the central zone of the terrane passed from early lawsonitic to subsequent epidote–almandine–glaucophane schist subfacies with the local development (east of the Nome River) of eclogitic assemblages.The high pressure metamorphic minerals were synkinematic with the development of mesoscopic-scale intrafolial isoclinal folds and a flattening foliation of consistent orientation. Initiation of uplift probably corresponded to the growth of barroisite rims on earlier sodic and actinolitic amphiboles, and partial post-kinematic greenschist facies replacements record later stages of decompression. Ophiolites and melange are not associated with the Seward Peninsula blueschists. The high-pressure metamorphism was caused by tectonic loading of a continental plate by an allochthon of indeterminate origin. The PT conditions of high pressure metamorphism were approximately 9–11 kbar, 400–450°C, thus falling between the PT paths of the Shuksan and Franciscan terranes.

Notes: Abstract Two periods of garnet growth (Gt1 and Gt2) have been found in the Finnmarkian nappes of north Norway. In the Kolvik Nappe (the lowest nappe) Gt1 has preserved an S2 syntectonic spiral inclusion fabric; in the Olderfjord Nappe an earlier S1 fabric and an interkinematic inter-D1–D2 fabric have been preserved in Gt1 whilst only the S1 fabric has been found in Gt1 in the Brennsvik Nappe (the highest nappe). In each nappe Gt2 overgrew a penetrative fabric (S2) wrapped around Gt1. In the Kolvik Nappe inclusion fabrics may be continuous from Gt1 into Gt2 but in the higher nappes there is a distinct break. Gt2 may have been partially syntectonic with D3 in the Brennsvik Nappe.Chemically Gt1 in the Kolvik Nappe and in parts of the Olderfjord and Brennsvik Nappes has antithetic Fe-Mn zoning. In all nappes XCa and XMg are weakly zoned in Gt1; XMg increases outwards and is greater in the higher nappes in Gt1 suggesting higher nucleation temperatures. In the Olderfjord and Brennsvik Nappes Gt2 is marked by increasing XCa, probably due to changing garnet-plagioclase equilibria, although the Fe/Mg ratio remains constant. XMg is higher in Gt2 than Gt1.Basement rocks within the nappe pile have an early pre-Finnmarkian growth (Gt1) and a later Finnmarkian growth (GtH) correlated with Gt2 on the basis of chemical zoning patterns.The diachroneity of Gt1 is ascribed to progressively earlier (compared to the structural development) cessation of overstepping of garnet-forming reactions before peak metamorphism in the higher nappes, resulting in earlier structural events being preserved.

Notes: Abstract Fluid inclusion studies of rocks from the late Archaean amphibolite-facies to granulite-facies transition zone of southern India provide support for the hypothesis that CO2,-rich H2O-poor fluids were a major factor in the origin of the high-grade terrain. Charnockites, closely associated leucogranites and quartzo-feldspathic veins contain vast numbers of large CO2-rich inclusions in planar arrays in quartz and feldspar, whereas amphibole-bearing gray gneisses of essentially the same compositions as adjacent charnockites in mixed-facies quarries contain no large fluid inclusions. Inclusions in the northernmost incipient charnockites, as at Kabbal, Karnataka, occasionally contain about 25 mol. % of immiscible H2O lining cavity walls, whereas inclusions from the charnockite massif terrane farther south do not have visibile H2OMicrothermometry of CO2 inclusions shows that miscible CH4 and N2 must be small, probably less than 10mol.%combined. Densities of CO2 increase steadily from north to south across the transitional terrane. Entrapment pressures calculated from the CO2 equation of state range from 5 kbar in the north to 7.5 kbar in the south at the mineralogically inferred average metamorphic temperature of 750°C, in quantitative agreement with mineralogic geobarometry. This agreement leads to the inference that the fluid inclusions were trapped at or near peak metamorphic conditions.Calculations on the stability of the charnockite assemblage biotite-orthopyroxene-K-feldspar-quartz show that an associated fluid phase must have less than 0.35 H2O activity at the inferred P and T conditions, which agrees with the petrographic observations. High TiO2 content of biotite stabilizes it to lower H2O activities, and the steady increase of biotite TiO2 southward in the area suggests progressive decrease of aH2O with increasing grade. Oxygen fugacities calculated from orthopyroxene-magnetite-quartz are considerably higher than the graphite CO2-O2 buffer, which explains the absence of graphite in the charnockites.The present study quantifies the nature of the vapours in the southern India granulite metamorphism. It remains to be determined whether CO2-flushing of the crust can, by itself, create large terranes of largeion lithophile-depleted granulites, or whether removal of H2O-bearing anatectic melts is essential.

Notes: Abstract There are discrete masses of un-deformed metabasite within the blueschist series of the island of Syros. Greece. Around the margins of these masses are zonal sequences through rocks showing intracrystalline deformation but without a geometric fabric, to rocks with discrete and anastomosing shear zones, and finally to penetratively foliated rocks with isolated relics of the original undeformed texture. Textural relics suggest that this spatial sequence is at least qualitatively also a temporal sequence.This progressive shear zone deformation took place concurrently with a glaucophane-epidote to eclogite reaction. The reaction pathways in the rocks that underwent the shear zone deformation can be compared with those in rocks of a similar composition that suffered a longer deformation history and show no relics of an undeformed parent. Although the final assemblages are in both cases the same, the pathways are different. These differences are in part related to reactions promoted by the change from local to bulk equilibrium on the onset of deformation in the rocks. They are also related to the crystallization and later breakdown during the sequence of progressive equilibration of a metastable phase, in this case an impure glaucophane.

Notes: Abstract The Rockley Volcanics from near Oberon, New South Wales occur within the aureole of the Carboniferous Bathurst Batholith and have been contact metamorphosed at P ∼ 100 ± 50MPa (10.5kbar) and a maximum T ∼ 565°C in the presence of a C–O–H fluid. Prior to contact metamorphism the volcanics were regionally metamorphosed and altered with the extensive development of actinolite, chlorite, plagioclase, quartz and calcite. The contact metamorphosed equivalents of these rocks have been subdivided into: Ca-poor (cordierite + gedrite), Mg-rich (amphibole + olivine + spinel), mafic (amphibole + plagioclase) and Ca-rich (amphibole + garnet + diopside; diopside + plagioclase; garnet + diopside + wollastonite) rocks.The chemistry of the minerals in the hornfelses was controlled by the bulk rock chemistry and fluid composition. Pargasites and hastingsites as well as an unusual phlogopite with blue green pleochroism, are found in Ca-rich hornfelses. A comparison of the assemblages with experimentally derived equilibria suggests that the fluid phase associated with the Ca-rich hornfelses was water-rich (Xco2= 0.1 to 0.3) while that associated with the Mg-rich hornfelses was enriched in CO2 (Xco2 〉 0.7). The different hornfels types have reacted to contact metamorphism independently in both their solid and fluid chemistries.

Notes: Abstract A garnet–hornblende Fe–Mg exchange geothermometer has been calibrated against the garnet–clinopyroxene geothermometer of Ellis & Green (1979) using data on coexisting garnet + hornblende + clinopyroxene in amphibolite and granulite facies metamorphic assemblages. Data for the Fe–Mg exchange reaction between garnet and hornblende have been fitted to the equation. In KD=Δ (XCa,g) where KD is the Fe–Mg distribution coefficient, using a robust regression approach, giving a thermometer of the form: with very satisfactory agreement between garnet–hornblende and garnet–clinopyroxene temperatures. The thermometer is applicable below about 850°C to rocks with Mn-poor garnet and common hornblende of widely varying chemistry metamorphosed at low aO2.Application of the garnet–hornblende geothermometer to Dalradian garnet amphibolites gives temperatures in good agreement with those predicted by pelite petrogenetic grids, ranging from 520°C for the lower garnet zone to 565–610°C for the staurolite to kyanite zones. These results suggest that systematic errors introduced by closure temperature problems in the application of the garnet–clinopyroxene geothermometer to the ‘calibration’data set are not serious. Application to ‘eclogitic’garnet amphibolites suggests that garnet and hornblende seldom attain Fe–Mg exchange equilibrium in these rocks.Quartzo-feldspathic and mafic schists of the Pelona Schist on Sierra Pelona, Southern California, were metamorphosed under high pressure greenschist, epidote–amphibolite and (oligoclase) amphibolite facies beneath the Vincent Thrust at pressures deduced to be 10±1 kbar using the phengite geobarometer, and 8–9kbar using the jadeite content of clinopyroxene in equilibrium with oligoclase and quartz. Application of the garnet–hornblende thermometer gives temperatures ranging from about 480°C at the garnet isograd through 570°C at the oligoclase isograd to a maximum of 620–650°C near the thrust. Inverted thermal gradients beneath the Vincent Thrust were in the range 170 to 250°C per km close to the thrust.

Notes: Coexisting Ca-poor and Ca-rich pyroxenes in granulites at Cape Riche, in the Precambrian Albany-Fraser Province, Western Australia, are dominantly chemically homogeneous within individual samples, suggesting a major episode of equilibration. However, occasional grains in a few samples contain exsolved domains interpreted as relics of an earlier, higher-T assemblage. Pyroxene pairs in ten, presumably isothermal, samples from a restricted area are used to (i) assess the suitability of several versions of the two-pyroxene thermometer for application to metamorphic rocks, and (ii) determine the thermal history of the Cape Riche pyroxenes.The various versions of the two-pyroxene thermometer applied to the well-equilibrated homogeneous pyroxene grains show poor to good precision and yield mean temperatures varying widely from 683° to 893°C, in the following order of increasing T: Lindsley (1983; opx version), 683°± 11°C; Kretz (1982; KD version), 705°± 19°C; Ross & Huebner (1975), 709°± 30°C; Kretz (1982; solvus version), 735°± 24°C; Fonarev & Graphchikov (1982; opx version), 〈750°C; Lindsley (1983; cpx version), 784°± 40°C; Fonarev & Graphchikov (1982; cpx version), ~820°± 30°C; Wood & Banno (1973), 849°± 16°C; Powell (1978), 854°± 23°C; Wells (1977), 893°± 10°C. Independent T estimates, based on mafic assemblages and garnet-biotite thermometry, suggest that the major episode of metamorphism occurred at 700-800°C (P ~ 5 kbar). Therefore the Wells, Powell, Wood & Banno and Fonarev & Graphchikov (cpx) temperatures are almost certainly too high. In the absence of a more precise independent T estimate it is difficult to assess the relative merits of the results obtained from the remaining versions of the two-pyroxene thermometer, none of which can be unequivocally demonstrated to be seriously in error, though the Lindsley (opx) T is probably too low. Other significant shortcomings evident in the results include the relatively poor precision obtained from the three methods based on purely graphical representation of the augite limb of the solvus (i.e., the Ross & Huebner, Fonarev & Graphchikov (cpx) and Lindsley (cpx) versions), and the apparent dependence of derived T on Mg/Fe2+ ratio for the Powell, Wood & Banno and Lindsley (cpx) methods.For the bulk compositions of exsolved domains, the different versions of the two-pyroxene thermometer yield mean temperatures 23° to 82°C (overall mean, 65°C) higher than for homogeneous grains in the same samples. These exsolved domains are interpreted as relics of a higher-T (peak?) metamorphic assemblage, rather than an igneous precursor.

Notes: This work presents the results of a fluid inclusion study of an amphibolite-granulite facies transition in West Uusimaa, S.W. Finland. Early fluid-inclusions in the granulite facies area are characteristically carbonic (CO2), in contrast to predominantly aqueous early inclusions in the amphibolite facies area. These early inclusions can be related to peak metamorphic conditions (750-820°C and 3-5 kbar for peak granulite facies metamorphism). Relatively young CO2 inclusions with low densities (〈0.8g/cm3) indicate that the first part of the cooling history of the rocks was characterized by a near isothermal uplift.N2-CH4 inclusions, with compositions ranging between pure CH4 and pure N2 (Raman spectral analysis), were found in the whole area. They are probably syn- or even pre-early inclusions. Only nearly critical homogenizing inclusions have been found (low density). Pressure estimates, based on densities of early fluid inclusions, show that the rapid transition of amphibolite towards granulite facies metamorphism is virtually isobaric. Granulite facies metamorphism in West Uusimaa is a thermal event, probably induced by the influx of hot, CO2-bearing fluids.

Notes: Multisystems of n+k (k 〉 3) phases are very complicated and knowledge of them has suffered as a result. The successful solution of the topological relationships in n+ 3 phase multisystems by Zen (1966, 1967) and Zen & Roseboom (1972) has aroused much interest regarding what will happen in a multisystem of more than n+ 3 phases. Since 1979, some important research results on this topic have been published. These results have expounded the substantial rules governing the appearance of phase relations in phase diagrams of n - k (k 〉 3) phase multisystems. The most significant conclusions include: (1) It is impossible to incorporate all the possible phase relations in an n+k (k 〉 3) phase multisystem in a single closed net. Therefore, it is no longer enough to use only a single closed net to depict the topological relations involved in these types of multisystems. Instead, one or more groups of closed nets, namely the complete system(s) of closed nets are necessary for this purpose. (2) A principle called the Combination Principle has been proposed and proved. It states: Any closed net of one n+k (k 〉 3) phase multisystem must be a combination of two or more distinct n+ 3 order submultisystem closed nets belonging to the given n+k phase multisystem, if it is not one of the n+ 3 order submultisystem closed nets itself. The combination principle provides both a theoretical basis and a practical method for the construction of closed nets and, hence, for the derivation of the real phase diagrams for any n+k (k 〉 3) phase multisystem. (3) A theorem on divariant-assemblage-characteristic-stability-polygons is also important to our understanding of the n+k (k± 3) phase multisystem closed nets. This theorem can be stated as follows: A divariant assemblage of an n+k (k± 3) phase multisystem will be stable in an l-polygon lacking diagonals in an appropriate set of closed-net-diagrams, and this l-polygon may be at least a triangle, and at most a k-polygon. In addition, the closed-net-diagrams of unary and binary n+ 4 phase multisystems derived respectively by Guo (1980b, 1980c, 1981a) and by Roseboom & Zen (1982) have also been summarized. The combination principle is applied to a practical petrological problem in this paper, dealing with 7 phases in the system FeO-Fe2O3-SiO2.

Notes: Abstract The stability of quartz-chloritoid-staurolite-almandine-cordierite and aluminium silicates is used to constrain both metamorphic conditions and pressure-temperature trajectories for two localities within the 2700 Ma Archaean Yilgarn Block in Western Australia. Available experimental data are used to calculate thermodynamic data for a self-consistent set of equilibria between these minerals. A lower amphibolite facies locality from the margin of a lower strain area contains assemblages including quartz-chloritoid-staurolite-garnet-biotite with altered cordierite replacing chloritoid, quartz-staurolite-andalusite, and quartz-cordierite-andalusite-biotite. This locality was heated to 530–560°C in the andalusite field, at 4.2 kbar. A sample from a mid- to upper-amphibolite facies, highly strained locality contains relict staurolite enclosed by andalusite, in turn replaced by cordierite and muscovite with biotite and sillimanite in the matrix. The assemblage was heated isobarically from conditions near the maximum experienced by the lower grade locality of 560°C at 4.2 kbar to temperatures in excess of the andalusite-sillimanite transition but within the quartz plus muscovite stability field (600–650°C). The higher grade locality is close to a granitoid dome and sections based on gravity profiles reveal that this locality is underlain by granitoid at shallow depths. The higher grade metamorphism apparently reflects superposition of the thermal aureole on regional metamorphic conditions similar to those in the lower grade areas.

Notes: Abstract A major system of steep Caledonian shear zones, of regional extent, has been identified in NE Scotland. The shear zones affect a wide range of lithologies, including Argyll and Southern Highland Group Dalradian, ‘Younger Basic’intrusives and their hornfelses, and also the earlier of the more acid intrusions. The observed fabrics and parageneses are consistent with low-pressure amphibolite facies metamorphism. These shear zones represent a phase of movement which occurred in the 490-465 Ma interval when ambient temperatures were still high, and it is concluded that this is the principal control on the metamorphic grade achieved within the shear zones, although local anomalies may exist.

Notes: Abstract An experimental study of the system CaCO3–MgCO3–FeCO3 was undertaken in order to calibrate the iron correction to the calcite–dolomite geothermometer, which is based on the solubility of magnesium in calcite in the assemblage calcite + dolomite. The experiments, at 450°C and lower temperatures, resulted in products with a very small grain size and incomplete equilibration. However, application of a carefully-devised automatic data processing algorithm to analyses of the phases in experimental charges, combined with a thermodynamic analysis, results in geothermometer diagrams which should be preferred to previous theoretical predictions.

Notes: Abstract Biotite, garnet, staurolite and kyanite isograds in pelitic metasedimentary rocks are developed as a result of thermal metamorphism around syntectonic granitoids in Eastern Rouergue (France). Temperature estimates range between 400°C and 650°C at about 6.5 kbar. Geothermobarometry shows a steep isobaric T gradient which is consistent with the interpretation that the metamorphic highs are thermal aureoles. High grade rocks show evidence of two staurolite forming reactions in the presence of plagioclase and the absence of chlorite that have not been described previously in the literature. The reaction that occurs in the middle staurolite zone, alm-rich ga + Ca-rich pla + Na-rich mu gro-rich ga + Na-rich pla + st + Na-poor mu, is considered to be prograde, whereas the reaction that occurs in the kyanite zone, alm-rich ga + Ca-rich pla + w st + Ca-rich ga + Na-rich pla + qz, is retrograde. The topology of these reactions is illustrated in terms of end member compositions for the systems KNaFASH and KCaFASH, respectively.

Notes: Chemical disequilibrium exists between all phases of the Alpe Arami garnet-peridotite body (Ticino, Switzerland) which hampers the evaluation of P-T conditions of origin, yet disequilibrium offers the inherent possibility to derive a P-T-t path for this mantle slice. We tried to tackle this problem by carrying out new mineral analyses and taking diffusion rates and bulk-rock compositional effects into consideration. Peak metamorphic conditions from mineral core compositions were estimated as 112050C/50.2 GPa. These values are significantly higher than previously published results and were determined from a combination of the O'Neill & Wood (1979) Fe/Mg garnet-olivine exchange thermometer and the Al-in-orthopyroxene barometer (Brey & Köhler, 1990), and are supported by the Ca/Cr ratios in garnet, which are in accord with these conditions. Details of the exhumation path were derived from (1) rim compositions of minerals that yield a first retrograde stage of 720 50C/2 0.25 GPa (2) a spinel lherzolite assemblage in narrow shear zones (tectonic phase F0″, after Möckel, 1969) which documents a second retrograde stage at 500–600C/0.8-l.5 GPa. The Ca content in olivine (Köhler & Brey, 1989) can be used to evaluate further P-T conditions along the retrograde path. We measured very low values (30–40 ppm Ca) in the cores of olivine and a remarkable increase towards the rim (120 ppm). The low core values may reflect an equilibrium stage during the main Alpine metamorphism. The increasing values towards the olivine rims probably represent a late-stage heating event. The initial cooling rates for the peridotite body are between 2700 and 5100C Ma-1, depending on which diffusion data are used.

Notes: The occurrence of lawsonite is described from pelitic schists of the lower-grade part of the pumpellyite-bearing subzone of the chlorite zone in the Asemi River area of central Shikoku. The lawsonite-bearing parageneses are consistent with the generally accepted view that the Sanbagawa facies series represents higher pressures than the lawsonite-bearing facies series in New Zealand.

Notes: Abstract Late Archaean orthogneisses and aluminous and iron-rich metasedimentary rocks intruded by anorthosite and a ferrodiorite-granite suite were completely recrystallized during Proterozoic granulite facies metamorphism. Geobarometry and geothermometry indicate P-T conditions of around 7.5kbar. 700°C, with a CO2-rich fluid phase and logfO2 at or below -16. A two-stage high-grade history of near isochemical corona growth is preserved in metasediments with the reaction cycle opx + plag + H2O → hbl+gar+SiO2→ opx+plag+H2O. End product compositions resemble those of the initial phases, and the only mobile components were SiO2 and/or H2O. The coronas reflect shortlived fluctuations in chemical activity at essentially constant P and T, contrary to simple progressive change in equilibrium parameters recorded by most corona-bearing textures.

Notes: In a polymetamorphic, felsic, biotite-bearing gneiss, biotite has reacted to form magnetite and microcline. The resulting structure is a magnetite core surrounded by a mantle of feldspar and quartz normally not exceeding 20mm in diameter. Measurements of oxygen isotope ratios disclose disequilibrium between mantle microcline and mantle quartz and also between mantle and matrix minerals of the same species. A clustering of temperature estimates from the oxygen isotope distribution between magnetite and quartz and between magnetite and microcline in the interval 550 to 600°C suggests an approach to oxygen isotope equilibrium. No signs of a re-equilibriation of the reacting biotite can be found.

Notes: Abstract Clinopyroxenes and garnets from 11 blueschist-facies Fe-rich eclogite samples from the Voltri Group show a wide range of chemical compositions. Detailed analyses of single pyroxene and garnet grains show wide and scattered chemical inhomogeneity, the KD(KD= (Fe2+/Mg)Gt/(Fe2+/Mg)Cpx) ranges from 20 to 87 based on rim analyses only. The data obtained indicate that the mineral pairs never attained equilibrium under uniform P-T conditions and that the compositions of the metamorphic minerals were influenced mainly by the composition of the pre-metamorphic minerals and by topotactical reactions.

Notes: Abstract At Sulitjelma, Norway, there is a major inversion of metamorphic isograds beneath an inverted but undisrupted ophiolite. The flysch-like Furulund schist in which the inverted isograds occur is also inverted and the early folds in it are downward facing. The isograds cut across the axial surfaces of early folds and across the schistosity. These relationships are explained as the consequence of metamorphism during the progressive development of a large overfold. The inverted limb of the overfold is regarded as a major, thick, gently-dipping shear zone, separating the lower-grade, lower part of the Caledonian allochthon below from the higher-grade upper part of the allochthon above. The association between stratigraphical inversion, downward-facing of syn-schistosity folds and metamorphic inversion is explained by the progressive development of the shear zone. It is suggested that the presence of such shear zones is a common feature of orogenic belts formed by continental collision.

Notes: Abstract The Hercynian granitic basement which forms the Tenda Massif in NE Corsica represents part of the leading edge of the European Plate during middle-to-late Cretaceous (Eoalpine) high P metamorphism. The metamorphism of this basement, induced by the overthrusting of a blueschist facies (schistes lustrés) nappe, was confined to a major ductile shear zone (c. 1000m thick) within which deformation increases upwards towards the overlying nappe. Metamorphism within the basement mostly records lower blueschist facies conditions (crossite + epidote) except near the base of the shear zone where the greenschist facies assemblage albite + actinolitic amphibole has developed instead of crossite. Study of the primary mafic phase breakdown reactions within hornblende granodiorite reveals the following metamorphic zonation. Zone 1: biotite to chlorite. Towards zone 2: biotite to phengite. Zone 2: Hornblende to actinolitic Ca-amphibole + albite + sphene, and biotite to actinolitic Ca-amphibole + albite + phengite + Ti-ore + epidote. Zone 3: Hornblende to crossite + low Ti-biotite + phengite + sphene, and biotite to crossite + low Ti-biotite + phengite + Ti-ore + sphene ± epidote. P-T conditions at the base of the shear zone are estimated to have been 390-490°C at 600-900 M Pa (6-9kbar) and the Corsican basement is therefore deduced to have been buried to 20-30 km during metamorphism. This relatively shallow metamorphism contrasts with some other areas in the Western Alps where the Eoalpine event apparently buried the European continental crust to depths of 80 km or more. As there is no evidence for a long history of blueschist facies metamorphism prior to the involvement of the European continent, it is deduced that the Eoalpine blueschists were produced during the collision of the Insubric plate with Europe, rather than during Tethyan intraoceanic subduction. Coherent blueschist terrains such as the schistes lustres probably record buovant feature collision and obduction tectonics rather than any preceding oceanic subduction.

Notes: Abstract Three major blastomylonitic synmetamorphic (epidote amphibolite to mid amphibolite facies) shear zones are seen on the NW coast of the Mullet Peninsula in NW Mayo. These shear zones occur at the contacts of major structural units and in an imbricated slice where rocks of the Erris Complex are deformed and chemically modified. Chemical changes associated with individual shear zones have been deduced by comparing the compositions of various gneisses both within and adjacent to the shear zones. Compositional changes are different in the constituent rock-types within each unit and many elements normally considered immobile have been selectively mobilized within the shear zones. Little evidence of wholesale metasomatic introduction of components into these shear zones was found to accompany the selective mobilization.

Notes: The High Himalayan Crystallines (HHC) of Bhutan were penetratively deformed, intruded by leucogranite and metamorphosed during the collision of the Indian and Asian plates. Metamorphic reaction textures in the HHC show that it experienced decompression while maintaining a laterally heterogeneous, and locally inverted, internal temperature range of c.600–750C. This thermal structure was produced by thrusting hot, migmatitic rocks over lower-grade rocks within the HHC and by the advection of heat from the intrusion of leucogranite dykes and sills during decompression. A variable velocity field within the HHC during exhumation and extrusion between India and Tibet caused the inversion of top to the south sense of shear present throughout most of the HHC to top down to the north shear near its top.

Notes: The Tormes Gneissic Dome (TGD, NW sector of the Iberian Massif, Spain) is a high-grade metamorphic complex affected by a major episode of extensional deformation (D2). The syn-D2 P-T path of the Lower Unit of the TGD was deduced from the analysis of reaction textures related to superimposed fabrics developed during exhumation, analysis of mineral zoning and thermobarometric calculations. It comprises an initial phase of decompression, determined using the tweequ thermobarometric technique, from 6.4–8.1 kbar at 735–750C (upper structural levels) and 7.2 kbar at 770C (lower structural levels) to 3.3–3.9 kbar and 645–680C. This evolution is consistent with the observed sequence of melting reactions and the generation of garnet-and cordierite-bearing anatectic granitoids. The later part of the syn-D2 P-T path consisted of almost isobaric cooling associated with the thermal re-equilibration of the unit in the new structural position. This segment of the P-T path is recorded by assemblages with And + Bt + Ms and Ms + Chi + Ab related to the later mylonitic S2 fabrics, which indicate retrogression to low-amphibolite and greenschist facies conditions.

Notes: Eclogite-grade metamorphism of the Seve Nappe Complex (SNC) in Norrbotten, Sweden, records the attempted subduction of the Baltic continental margin during the early Palaeozoic evolution of the Iapetus Ocean. Metamorphic titanite sampled from several calcsilicate gneisses of the SNC in Norrbotten occurs as part of a prograde, eclogite facies metamorphic mineral assemblage and yields concordant to nearly concordant U/Pb ages of 500–475 Ma. Later structural disruption of these rocks occurred during the Siluro-Devonian Scandian phase of the Caledonide orogeny, but the U/Pb systematics show no evidence of a second generation (metamorphic or recrystallized) of titanite, or of post-Early Ordovician disturbance through Pb loss. Hence the U/Pb ages are believed to record the time of prograde mineral growth during eclogite facies metamorphism of the SNC.These results support earlier Sm/Nd and 40Ar/39Ar studies indicating an Early Ordovician metamorphic age for the eclogitic Norrbotten SNC, and confirm the Early Ordovician destruction of at least this segment of the Palaeozoic passive margin of Baltica. These results indicate that the SNC in the northern Scandinavian Caledonides was subducted and metamorphosed to high grade some 50–70 Myr prior to the high-grade metamorphism of the SNC in the central Scandinavian Caledonides. This result requires significantly different early Palaeozoic tectonic histories for rocks mapped as SNC in the northern Caledonides and those in the central Caledonides, despite a seemingly similar tectonostratigraphic position and broadly similar high-grade metamorphism.

Notes: A suite of garnet-wollastonite-scapolite-bearing calcsilicate granulites from the Eastern Ghats has been investigated to document the controls of mineral reactions during the metamorphic evolution of the deep continental crust. The rocks studied show heterogeneity in modal mineralogy and phase compositions in millimetre-sized domains. Textural relations, and the compositional plots of the phases, established that the clinopyroxene exerts a strong influence on the formation and composition of garnet in the complex natural system. P-T estimates using the vapour-independent equilibria involving garnet define a near isobaric cooling path from c. 850C at c. 5.5–5.2 kbar. The deduced trajectory tallies well with the terminal segment of the overall retrograde P-T path construed from the associated rocks using well-calibrated thermobarometers. The ubiquitous occurrence of wollastonite and scapolite in the main calcsilicate body suggests low aCO2 during peak metamorphic condition. Fluid compositions constrained from mineral-fluid equilibria of the garnet-bearing assemblages show domainal variations as a function of the compositions of the solid phases, e.g. garnet and clinopyroxene. A quantitative log/CO2-log/O2 diagram has been constructed to depict the stability of the different calcsilicate assemblages as functions of the compositions and the behaviour of these fugitive species. The results of the mineral-fluid equilibria and the quantitative fluid/rock ratio calculations, in conjunction with the topological constraints, imply vapour-deficient meta-morphism in the rocks studied. It is argued that fO2 during peak metamorphism was monitored by the ambient fO2. Subsequently, during retrogression, different domains evolved independently, whereas the fluid composition was controlled by the mineral-fluid equilibria.

Notes: The Mallee Bore area in the northern Harts Range of central Australia underwent high-temperature, medium-to high-pressure granulite facies metamorphism. Individual geothermometers and geobarometers and average P-T calculations using the program Thermocalc suggest that peak metamorphic conditions were 705–810C and 8–12 kbar. Partial melting of both metasedimentary and meta-igneous rocks, forming garnet-bearing restites, occurred under peak metamorphic conditions. Comparison with partial melting experiments suggests that vapour-absent melting in metabasic and metapelitic rocks with compositions close to those of rocks in the Mallee Bore area occurs at 800–875C and 〉9–10 kbar. The lower temperatures obtained from geothermometry imply that mineral compositions were reset during cooling. Following the metamorphic peak, the rocks underwent local mylonitization at 680–730C and 5.8–7.7 kbar. After mylonitization ceased, garnet retrogressed locally to biotite, which was probably caused by fluids exsolving from crystallizing melts. These three events are interpreted as different stages of a single, continuous, clockwise P-T path. The metamorphism at Mallee Bore probably occurred during the 1745–1730 Ma Late Strangways Orogeny, and the area escaped significant crustal reworking during the Anmatjira and Alice Springs events that locally reached amphibolite facies conditions elsewhere in the Harts Ranges.

Notes: Abstract. Crops grown on virgin upland Vertisols of Zambia, are reported to perform rather poorly. However, subsoiling followed by repeated cultivation over two years apparently improves crop growth. Highest yields were recorded under long-term cultivation (12 years). To evaluate the reasons for these differences in crop response to Vertisol management, physical and hydrodynamic characteristics of soil profiles were studied in three soil management systems. The management systems were: uncultivated or virgin land; land cultivated for two years; and land cultivated for 12 years. The mean soil aggregate size decreased with increased time of cultivation, mostly due to the decrease of the largest sized aggregates. The surface horizon dried more slowly on the long-term cultivation plot. A comparison of the hydraulic conductivities indicated that water intake in the deeper layers improved with increased period in cultivation. Oxygen diffusion measurements showed good aeration at field capacity, to a depth of 0.32m on the long-term cultivation plots, but only to 0.17 m and 0.25 m for 2 years cultivation and virgin plots respectively. Repeated cultivation was beneficial in improving surface soil tilth and in improving subsurface drainage, thus removing the problem of a perched water table which occurred close to the soil surface under natural conditions.

Notes: Abstract. The chemical extractability of heavy metals introduced into the soil during 7 years application of sewage sludge, composted municipal solid waste and sheep manure, and their availability to citrus plants were studied. The total content of metals in the soil (0-20 cm)was increased by the use of sludges and compost, but only the Ni content in the saturation extracts of soil was significantly increased. Total Cd, Cr, Cu, Ni, Pb, and Zn were sequentially fractionated into water-soluble plus exchangeable, organically bound, carbonate-associated, and residual fractions. Most of the heavy metals were present in carbonate and residual fractions, although substantial amounts of water-soluble plus exchangeable Cd, and organically bound Cu and Ni were found. No significant increases in the metal contents in leaves and orange fruits were observed, with the exception of Pb in leaves. Several statistically significant correlations between metal content in plants, metal content in soil fractions, and chemical characteristics of soil were also found.

Notes: Book reviewed in this article: Human impact on Erosion and Sedimentation By D. E. Walling & J.-L. Probst (editors).

Notes: Book reviewed in this article: Soil erosion by water in Africa: Principles, Prediction and Protection By D. Nill, U. Schwertmann, U. Sabel-Koscella, M. Bernhard & J. Breuer.

Notes: Abstract. To provide a practical aid to improving fertilizer practice a mechanistic model was developed that can be readily calibrated for widely different crops. Most of the inputs are easy to obtain and the others, the amounts of fixed soil-K and the velocity constants for fixation and release of soil-K, can be readily measured by a novel procedure which is described.The model calculates for each day the potential increase in plant weight and the increment in root length, from the current plant mass, its %K and pan evaporation. It calculates the maximum amount of K that could be transported through soil to the root surfaces. It modifies this potential uptake by taking account of the ‘feedback’ of plant K on root absorption to give the actual uptake and a new %K in the plant. It calculates the radii of the depletion zones around each root increment and the interchange between the solution, exchangeable and fixed-K in these zones and also in the undepleted regions of soil. Routines are included for the effects of weather on the various processes. Differences between species are accommodated by selecting one of three algorithms for root growth and by adjusting the values of two crop-K parameters that define the decline in a critical and a maximum possible %K with increase in plant mass per unit area.A simplified version of the model runs interactively on the Internet at:

Notes: Abstract. The effect of rate and timing of autumn/winter straw incorporation on the immobilization of spring-applied N-fertilizer are studied. The immobilization of 15N-labelled fertilizer by straw was determined in pot trials with a sandy loam soil (Wick series) collected from two field experiments. In experiment 1, straw was incorporated at four different rates in the autumn; experiment 2 had a fixed rate of straw (7.5 t/ha) incorporated at monthly intervals from September to March. Immobilization in spring was not enhanced when only stubble was incorporated in autumn. However, autumn incorporation of 7.5 t/ha straw resulted in a significant increase in the immobilization of spring-applied N, equivalent to 10 kg/ha; when 15 t/ha straw was incorporated, immobilization increased to 18 kg/ha. The enhancement of immobilization, immediately following fertilizer application, was dependent on the extent of straw decomposition prior to N application. Thus immobilization was related to cumulative thermal time (day °C above 0°C; Tsum between the date of straw incorporation and fertilizer application). Straw which had been incorporated for Tsum 〉 1200 no longer caused appreciable immobilization of spring fertilizer.

Notes: Book reviewed in this article: Erosion and sediment yield: global and regional perspectives Edited by D. E. Walling and B. W. Webb.

Notes: Abstract. The restorative ability of herbaceous (Psophocarpus palustris, Pueraria phaseoloides) and woody (Leucaena leucocephala, Senna siamea, Acacia leptocarpa, Acacia auriculiformis) legume species and of natural regrowth was studied on an eroded and compacted Oxic Paleustalf in southwestern Nigeria. Compared to the control treatment that was continuously cropped for 15 years, four years of fallowing significantly improved test crop yields. However, fallowing with the above species did not substantially improve soil properties, particularly soil bulk density. A longer fallow period may be needed to amend soil physical conditions of this degraded Alfisol. Soil chemical properties were greatly improved following land clearing and plant biomass burning in 1993. However, the residual effect of burning on soil fertility was insignificant in the second cropping year. Among the fallow species, P. palustris and natural fallow showed the best residual effect on test crop performance. Despite the high biomass and nutrient yields of S. siamea and A. auriculiformis, test crop yields on these plots were low due to the border effects from the uncleared and fallowed subplots.

Notes: Abstract. To study the influence of different vegetation species and plant properties on the generation of surface runoff and soil erosion in south east Spain, a series of rainfall simulation experiments was conducted on small (c. 1.5 m2) plots. These were carried out in October 1993 and May 1994 on two sites close to Murcia. Six vegetation types were studied, with some at different stages of maturity, giving a total of nine vegetation treatments and two bare soil treatments. Four replicates of each treatment were exposed to a rainstorm of 120 mm/h for 15 minutes. The results of the experiments show that there are few significant differences in the ability of the vegetation types studied to control runoff or soil erosion. Of the plant properties considered, only plant canopy cover showed a significant relationship with soil loss and runoff with the greatest reduction in soil loss taking place at canopy covers greater than 30%. The implications of this research are that future efforts should be directed at developing ecological successions and revegetation methods which promote a substantial and sustainable canopy cover.

Notes: Abstract. The effect of superficial liming of acidic forest soils on CO2 and N2O emissions and CH4 uptake was investigated with closed chambers in two deciduous and two spruce forests, by weekly to biweekly measurements over at least one year. The flux rates of untreated areas varied between 1.94 and 4.38 t CO2-C/ha per y, 0.28 and 2.15 kg/N2O-N/ha per y and between 0.15 and 1.06 kg CH4-C/ha per y. Liming had no clear effect on CO2 emissions which may change in the long-term with decreasing root turnover and increasing C-mineralization. Apart from one exception, liming resulted in a reduction of N2O emissions by 9 to 62% and in an increase of CH4 uptake by 26 to 580%. The variability in N2O emissions between the forest sites could not be explained. In contrast, the variability of annual CH4 uptake rates could be explained by N content (r2= 0.82), C content (r2= 0.77), bulk density (r2= 60), pore space (r2= 0.59) and pH (r2= 0.40) of mineral soil at a depth of 0 to 10 cm, and by the quantity of material in the organic layer (r2= 0.66). Experiments with undisturbed columns of the same soils showed that between 1 and 73% of the total N2O emissions came from the organic layer. However, atmospheric CH4 was not oxidized in this layer, which represents a diffusion barrier for atmospheric CH4. When this barrier was removed, CH4 uptake by the mineral soil increased by 25 to 171%. These results suggest that liming of acidic forest soils causes a reduction of the greenhouse gases N2O and CH4 in the atmosphere, due to changes in the chemical, biological, and physical condition of the soils.

Notes: Abstract. Agricultural soils, having been depleted of much of their native carbon stocks, have a significant CO2 sink capacity. Global estimates of this sink capacity are in the order of 20-30 Pg C over the next 50-100 years. Management practices to build up soil C must increase the input of organic matter to soil and/or decrease soil organic matter decomposition rates. The most appropriate management practices to increase soil C vary regionally, dependent on both environmental and socioeconomic factors.In temperate regions, key strategies involve increasing cropping frequency and reducing bare fallow, increasing the use of perennial forages (including N-fixing species) in crop rotations, retaining crop residues and reducing or eliminating tillage (i.e. no-till). In North America and Europe, conversion of marginal arable land to permanent perennial vegetation, to protect fragile soils and landscapes and/or reduce agricultural surpluses, provides additional opportunities for C sequestration.In the tropics, increasing C inputs to soil through improving the fertility and productivity of cropland and pastures is essential. In extensive systems with vegetated fallow periods (e.g. shifting cultivation), planted fallows and cover crops can increase C levels over the cropping cycle. Use of no-till, green manures and agroforestry are other beneficial practices. Overall, improving the productivity and sustainability of existing agricultural lands is crucial to help reduce the rate of new land clearing, from which large amounts of CO2 from biomass and soil are emitted to the atmosphere.Some regional analyses of soil C sequestration and sequestration potential have been performed, mainly for temperate industrialized countries. More are needed, especially for the tropics, to capture region-specific interactions between climate, soil and management resources that are lost in global level assessments.By itself, C sequestration in agricultural soils can make only modest contributions (e.g. 3-6% of total fossil C emissions) to mitigating greenhouse gas emissions. However, effective mitigation policies will not be based on any single ‘magic bullet’ solutions, but rather on many modest reductions which are economically efficient and which confer additional benefits to society. In this context, soil C sequestration is a significant mitigation option. Additional advantages of pursuing strategies to increase soil C are the added benefits of improved soil quality for improving agricultural productivity and sustainability.

Notes: Abstract. Field measurement of landfill methane (CH4) emissions indicates natural variability spanning more than seven orders of magnitude, from less than 0.0004 to more than 4000 g/m2 per day. This wide range reflects net emissions resulting from production (methanogenesis), consumption (methanotrophic oxidation), and gaseous transport processes. The determination of an ‘average’ emission rate for a given field site requires sampling designs and statistical techniques which consider spatial and temporal variability. Moreover, particularly at sites with pumped gas recovery systems, it is possible for methanotrophic microorganisms in aerated cover soils to oxidize all of the CH4 from landfill sources below and, additionally, to oxidize CH4 diffusing into cover soils from atmospheric sources above. In such cases, a reversed soil gas concentration gradient is observed in shallow cover soils, indicating bidirectional diffusional transport to the depth of optimum CH4 oxidation. Rates of landfill CH4 oxidation from field and laboratory incubation studies range up to 166 g/m2 per day, among the highest for any natural setting, providing an effective natural control on net emissions. It has been shown that methanotrophs in landfill soils can adapt rapidly to elevated CH4 concentrations with increased rates of CH4 oxidation related to depth of oxygen penetration, soil moisture, and the nutrient status of the soil.Estimates of worldwide landfill CH4 emissions to the atmosphere have ranged from 9 to 70 Tg/y, differing mainly in assumed CH4 yields from estimated quantities of landfilled refuse. At highly controlled landfill sites in developed countries, landfill CH4 is often collected via vertical wells or horizontal collectors. Recovery of landfill CH4 through engineered systems can provide both environmental and energy benefits by mitigating subsurface migration, reducing surface emissions, and providing an alternative energy resource for industrial boiler use, on-site electrical generation, or upgrading to a substitute natural gas. Manipulation of landfill cover soils to maximize their oxidation potential could provide a complementary strategy for controlling CH4 emissions, particularly at older sites where the CH4 concentration in landfill gas is too low for energy recovery or flaring. For the future, it is necessary to better quantify net emissions relative to rates of CH4 production, oxidation, and transport. Field measurements, manipulative studies, and model development are currently underway at various spatial scales in several countries

Notes: Book Reviewed in this article: Phosphorus loss from soil to water: Edited by H. Tunney, O. T. Carton, P. C.

Notes: Abstract. Variously timed sub-optimal irrigation strategies were applied to sugarbeet grown on a light soil (loamy sand or sandy loam) over four seasons (1991 to 1994) to investigate the effect on crop growth and nitrate leaching risk. Data from the two dry seasons, (1991 and 1994) are reported here. In the driest year (1991) soil mineral N levels after autumn harvest were negatively related to crop water use (P 〈 0.05). In this season, there was little drainage from the soil profile, and full irrigation reduced residual soil N by 31 kg N/ha (0-90 cm) compared with the unirrigated treatment (79 kg N/ha). The potential for N leaching during the ensuing winter was consequently more than halved. In 1991 and 1994 there was a strong positive linear relationship between dry matter yield, N uptake and water use, but a negative relationship between plant N concentration and water use. These relationships were a function of the severity and not the timing of drought. The additional N uptake associated with increased irrigation and crop water use was biased towards a large concentration in the aboveground crop (tops), which are normally returned to the soil. The C:N ratio of sugarbeet tops was affected by crop water supply with droughted crops having lower values. This would also influence N release and subsequent leaching risk. However, the effects of drought on N leaching risk were relatively small when compared with other root crops such as potatoes.

Notes: Abstract. The effects of tree crops on the soil physical properties of former agricultural land were compared with those of ley in a rotation with cereals on adjacent sites. Five sites in southern Sweden were investigated focussing on soil water retention characteristics, dry bulk density, macroporosity and saturated hydraulic conductivity. Three of the sites were on light textured soils and two on clay soils. The tree crops were 30 to 35-year-old hybrid aspen, Populus deltoides, and silver birch, Betula pendula, and the ley crops were one to five years old.The light-textured soils under tree crops showed bimodal pore size distributions in the macropore region, whereas under ley crops they showed unimodal distributions. Dry bulk densities were generally smaller and the macroporosities larger under tree crops compared with leyicereal crops. Saturated hydraulic conductivities tended to be larger under tree crops. Slopes of the linear regression lines between saturated hydraulic conductivity and each of the parameters dry bulk density, porosity and macroporosity were steeper in the soil under agricultural crops than under tree crops.Observed differences in physical properties were considered to be an effect of land use, which had brought about changes in aggregate stability, pore size distribution and pore continuity.

Notes: Abstract. Phosphorus concentrations and outputs have been compared and contrasted in six small agricultural catchments in the west and northeast of Scotland. The loss of P from soils to stream waters was more from catchments with intensive dairy cattle farming in the west than from the less intensively stocked/arable catchments in the northeast, with striking differences being seen between the two regions. In the northeast, intensive animal farming caused less P loss in drainage water than arable management.Larger mean annual concentrations were seen in the west (0.076-0.142 mg PO4-P/l as molybdate-reactive phosphate–MRP) compared with the northeast (0.012-0.025 mg PO4-P/l), a feature caused by the combination of limited P-retention in the western Gleysols and smaller inputs to the largely-podzolic northeastern catchments. Stream concentrations were decreased by dilution during winter storm flows and increased during summer baseflow and at the beginning of soil rewetting in autumn.

Notes: Book Reviewed in this article: Freshwater Contamination By B. Webb (editor).

Notes: Book Reviewed in this article: Biotechnical and soil bioengineering slope stabilization. A practical guide for erosion control By D. H. Gray & R. B. Sotir.

Notes: Abstract. This paper reports results from a four year study to investigate the suitability of porous ceramic cups to measure solute leaching on shallow chalk soils. Measurements were carried out in one field following surface applications of nitrate and bromide tracers and in two fields after only bromide was applied. Soil water samples were collected from porous cups at 30,60 and 90cm depth after every 25 mm of drainage, and soil samples from 0–30, 30–60 and 60–90 cm were collected monthly eachwinter. Soil matric suctions andvolumetric moisture content were measured in one winter. Leaching losses, measured with ceramic cups were compared with those measured by soil analysis. Porous cups installed in chalk at 60 and 90 cm depth were only able to collect samples regularly when soil matric suctions were less than 15 kPa. Water held at such low suctions is likely to move quickly through relatively large fissures in the chalk. The slow rate of equilibration between solute concentrations in water moving in macrofissures and those in water moving through micropores of the chalk matrix, means that porous cups may not provide good estimates of leaching losses if they are installed in chalk rock.

Notes: Abstract. Nitrate leaching after one year of a cut grass/clover ley was measured in two succeeding years to investigate how the postponing of ploughing leys from early to late autumn or spring, in combination with spring or winter cereals affected leaching of nitrate. The experiment was conducted as three field trials, two on a coarse sandy soil and one on a sandy loam soil. For calculation of nitrate leaching, soil water samples were taken using ceramic suction cups. The experiments started in spring in a first year ley and ended in spring three years later. Total nitrate leaching for the three year periods for each trial ranged between 160–254 and 189–254 kg N/ha on the coarse sand and 129–233 kg N/ha on the sandy loam. The results showed that winter wheat (Triticum aestivum L.) did not have the potential for taking up the mineralized N in autumn after early autumn ploughing of grass/clover leys, and that the least leaching was generally found when ploughing was postponed until spring, and when winter rye (Secale cereale L.) was grown as the second crop rather than spring barley (Hordeum vulgare L.). Nevertheless, leaching was generally high in the winter period even when winter rye was grown. On these soil types ploughing out should be postponed, whenever possible, to spring. Crop systems that maximize the utilization of mineralized N and thereby minimize nitrate leaching need to be further developed. Based on N balances, the data were further used to estimate the biological N fixation by the clover.

Notes: Abstract. Ceramic suction cups were used to obtain samples of soil solution from permanently grazed swards receiving 200 kg N/ha/y. The suction cups were installed in 1 ha plots at 10, 30 and 60 an depth in a poorly drained, heavy clay soil in S. W. England. The plots were hydrologically isolated from each other by perimeter drains which channelled surface runoff water into v-notch weirs. In one treatment, artificial drainage by a system of field and mole drains also converged to outfalls through v-notch weirs, which enabled samples to be taken. Nitrate and a range of other ionic constituents were examined over a 12 month period in soil solutions taken from the suction cups and compared with leachate obtained from the field drains and surface channels. Field drain samples frequently exceeded the EC limit of 11.3 mg nitrate-N/1, but concentrations in suction cups obtained during the same period did not, and were up to ten-fold less. Although correlations for ions were found between different sampling depths and drainage samples, no clear patterns emerged. It was concluded that suction cups were inappropriate for the determination of the overall leaching losses in this soil type, but provided useful data on changes in ionic concentrations which occurred in different soil horizons through to drainage outfalls.

Notes: Abstract. The impact of soil erosion on soil productivity was estimated for a Rhodic Ferralsol and a Eutric Cambisol in Santa Catarina, southern Brazil. Over equivalent periods, total soil losses were an order of magnitude different (868 and 68 t/ha respectively on the bare soil control), yet the impact on maize yield per tonne of soil lost was far greater at the Cambisol site with less erosion. Similar interesting contrasts between sites were found for the other measures of impact with decline in pH and phosphorus and increase in free aluminium being the most obvious induced soil differences. The results demonstrate the variable nature of erosion impact according to soil type and they highlight the importance of examining a number of measures of impact before pronouncing on the sustainability of any particular agricultural practice.

Notes: Abstract. Mubangwe Farm, northern Malawi, was brought into cultivation from savanna vegetation with Brachystegia between 1970 and 1983 to produce tobacco, maize and groundnuts. Because of poor yields even with inputs of lime, N, P and K the fields were soon abandoned. The soils were only moderately acidic with little likelihood of Al toxicity. They held only small amounts of exchangeable Ca2+ (down to 0.01 cmolc/kg) particularly at depth. Phosphorus availability was low particularly in the subsoil. A minus-one pot experiment showed that the growth of sorghum in topsoil samples was limited by lack of N, P, S and Ca. The lower availabilities of P and Ca in the subsoil are therefore likely to be major limitations to growth, allowing only limited root penetration. The loamy sand to sandy clay soils generally had small available water capacities (down to 0.07 cm3/cm3) which, with restricted root development, may have lead to drought in dry periods during the growing season. The findings emphasize the need to measure both subsoil and topsoil properties when new areas of land are being developed for crop production.

Notes: Abstract. Nitrogen (N) leaching losses from a shallow limestone soil growing a five course combinable croprotation (oilseed rape, wheat, peas, wheat, barley) were measured from 1990 until 1995 using porous ceramic cups, at 60 cm depth, and drainage estimates. The crops were grown with three husbandry systems and two levels of N fertilizer. The husbandry systems were designed to reflect local practice (Standard), the best possible techniques to reduce N loss (Protective) and an Intermediate system which was a compromise between the two. Nitrogen was applied at full and half recommended rates. Drainage started during September in four years and November in one year, with above average drainage in three years. Losses of N were largest after peas (58 kg/ha) and oilseed rape (42 kg/ha), and least (17 kg/ha) before peas sown in spring after a cover crop. Over five years, the Protective management system, which used early sowing and shallow cultivation wherever possible, lost least N (31 kg/ha/y) and the Standard system, with conventional drilling dates and ploughing as the primary cultivation, lost most (49 kg/ha/y). Halving the N fertilizer decreased N loss by 11 kg/ha/y, averaged over the rotation. None of the treatments gave mean drainage water nitrate concentrations of less than 50 mg/l, averaged over the five years. Changes to arable cropping alone will not eliminate the need for other measures to control nitrate concen-trations in public drinking water supplies.

Notes: Abstract. Soil salinity and alkalinity reduce plant production and alter species composition of meadow grasslands in western Jilin Province, China. This study was designed to compare the survival and growth of three grass species (Aneumlepidium chinense, Puccinellia tenuijlora and Hordeum brevisubulatum) transplanted into saline-alkali soils in the field, and to evaluate the effects of gypsum amendments on soil properties and growth of these species. Gypsum treatments decreased soil pH, electrical conductivity, and chloride and sodium levels; water infiltration and calcium levels were increased. Survival of grass transplants was increased by gypsum treatments. Tiller number and height, and grass yields were all increased by the application of gypsum. Improvements in plant growth and survival with gypsum treatment appeared to be due to reduced chloride levels and increased Ca availability in the soil, and to changes in soil structure leading to improved infiltration rates. Revegetation of salinelalkaline soils in this region would be improved by application of gypsum in the range of 14–19 t/ha.

Notes: Abstract. Methane (CH4) is an important greenhouse gas. Flooded rice fields (paddies) are a significant source of atmospheric CH4; estimates of the annual emission from paddies range from less than 20 to 100 million Tg, with best estimates of 50 × 20 Tg. The emission is the net result of opposing bacterial processes: production in anaerobic microenvironments, and consumption and oxidation in aerobic microenvironments, both of which occur sequentially and concurrently in flooded rice soils. With current technologies, CH4 emission from rice fields will increase as production increases. Over the next 25 years rice production will have to increase by 65% from the present 460 Mt/y to 760 Mt/y in 2020. The current understanding of the processes controlling CH4 fluxes, rice growth and rice production is sufficient to develop mitigation technologies. Promising candidates are changes in water management, rice cultivars, fertilization, and cultural practices. A significant reduction of CH4 emission from rice fields, at the same time that rice production and productivity increase at the farm level, is feasible, although the regions where particular practices can be applied, and the trade-offs that are possible, have still to be identified.

Notes: Abstract. Increases in the emissions of globally important nitrogen (N) oxide gases have coincided with significant changes in land use in the tropics. Clearing of tropical forests and savannas for agriculture currently represents the most extensive alteration of land cover on the planet. Over the last several decades, N fertilizer use has increased globally, and in China and the developing world, use has recently surpassed that in the developed world. The potential contribution of land-use change in the tropics to the increase in N oxides is great, yet only a few studies have measured N oxide emissions after tropical land conversion. Our summary of available research shows some conversions to pastures and a few management practices, especially those using N fertilizers, increase emissions beyond those found in undisturbed ecosystems. However, not all studies show unequivocal increases in emissions. Accordingly, we call for a mechanistic understanding of the processes controlling trace gas fluxes to adequately predict under what conditions increased emissions may occur. More measurements are needed to build and test models that may improve management of N fertilizer use in tropical agricultural systems. Given the expected expansion of agriculture and increased use of N fertilizers in the tropics, increased emissions of N oxides from the tropics are likely.

Notes: Abstract. Grazing animals on managed pastures and rangelands have been identified recently as significant contributors to the global N2O budget. This paper summarizes relevant literature data on N2O emissions from dung, urine and grazed grassland, and provides an estimate of the contribution of grazing animals to the global N2O budget.The effects of grazing animals on N2O emission are brought about by the concentration of herbage N in urine and dung patches, and by the compaction of the soil due to treading and trampling. The limited amount of experimental data indicates that 0.1 to 0.7% of the N in dung and 0.1 to 3.8% of the N in urine is emitted to the atmosphere as N2O. There are no pertinent data about the effects of compaction by treading cattle on N2O emission yet. Integral effects of grazing animals have been obtained by comparing grazed pastures with mown-only grassland. Grazing derived emissions, expressed as per cent of the amount of N excreted by grazing animals in dung and urine, range from 0.2 to 9.9%, with an overall mean of 2%. Using this emission factor and data statistics from FAO for numbers of animals, the global contribution of grazing animals was estimated at 1.55 Tg N2O-N per year. This is slightly more than 10% of the global budget.

Notes: Abstract. Increases in the atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and to ozone depletion in the stratosphere. Nitric oxide (NO) is a cause of acid rain and tropospheric ozone. The use of N fertilizers in agriculture has direct and indirect effects on the emissions of both these gases, which are the result of microbial nitrification and denitrification in the soil, and which are controlled principally by soil water and mineral N contents, temperature and labile organic matter.The global emission of N2O from cultivated land is now estimated at 3.5 TgN annually, of which 1.5 Tg has been directly attributed to synthetic N fertilizers, out of a total quantity applied in 1990 of about 77Tg N. This amount was 150% above the 1970 figure. The total fertilizer-induced emissions of NO are somewhere in the range 0.5-5 Tg N. Mineral N fertilizers can also be indirect as well as direct sources of N2O and NO emissions, via deposition of volatilized NH3 on natural ecosystems and denitrification of leached nitrate in subsoils, waters and sediments.IPCC currently assume an N2O emission factor of 1.25 ± 1.0% of fertilizer N applied. No allowance is made for different fertilizer types, on the basis that soil management and cropping systems, and unpredictable rainfall inputs, are more important variables. However, recent results show substantial reductions in emissions from grassland by matching fertilizer type to environmental conditions, and in arable systems by using controlled release fertilizers and nitrification inhibitors. Also, better timing and placement of N, application of the minimum amount of N to achieve satisfactory yield, and optimization of soil physical conditions, particularly avoidance of excessive wetness and compaction, would be expected to reduce the average emission factor for N2O. Some of these adjustments would also reduce NO emissions. However, increasing global fertilizer use is likely to cause an upward trend in total emissions even if these mitigating practices become widely adopted.

Notes: Abstract. The validity of the model described in Greenwood & Karpinets (1997) was tested against the results of single year, multi level K fertilizer experiments. Measurements of plant mass, %K in the plant and K activity ratio in soil had been made at harvest and at intervals during the growing season on spring wheat, summer cabbage and turnips. Reasonably good agreement was obtained between these measurements and simulated values when the two ‘crop’ parameters (defining the dependence of critical and maximum possible %K on plant mass) were adjusted for each crop. Also good agreement was generally obtained for plant weight and plant %K at harvest in less detailed experiments on 10 other crops. Values of the two ‘crop’ parameters for 12 of the crops were strongly correlated with one another suggesting that a single ‘crop’ parameter may be all that is required to define most inter-species differences in plant-K demand.Simulations with the model indicate that, in central England, no response of 10 crops to K fertilizer would be likely on soils containing more than 170 mg of 1 M ammonium nitrate extractable-K/kg of soil and having clay contents of between 15 and 45%. Shortcomings of the model and opportunities for advance are discussed.A simplified version of the model runs on the Internet at:

Notes: Abstract. As part of a study of recession farming on the ‘fadama’ lands on a segment of the Komadugu-Yobe floodplain, a survey was carried out to investigate the local farmers’ perception of soil types and management practices. The farmers are clearly aware of the differences in soil type on the fadama and they possess unique skills in managing their farm lands. The farmers classify fadama soils for recession farming by assessing soil texture and soil drainage conditions by feel and observation. Integrating such local knowledge into soil surveys will lead to better practical definition of mapping units and give soil names that have more meaning for the farmers.

Notes: Abstract. The large boreal peatland ecosystems sequester carbon and nitrogen from the atmosphere due to a low oxygen pressure in waterlogged peat. Consequently they are sinks for CO2 and strong emitters of CH4. Drainage and cultivation of peatlands allows oxygen to enter the soil, which initiates decomposition of the stored organic material, and in turn CO2 and N2O emissions increase while CH4 emissions decrease. Compared to undrained peat, draining of organic soils for agricultural purposes increases the emissions of greenhouse gases (CO2, CH4, and N2O) by roughly 1t CO2 equivalents/ha per year. Although farmed organic soils in most European countries represent a minor part of the total agricultural area, these soils contribute significantly to national greenhouse gas budgets. Consequently, farmed organic soils are potential targets for policy makers in search of socially acceptable and economically cost-efficient measures to mitigate climate gas emissions from agriculture. Despite a scarcity of knowledge about greenhouse gas emissions from these soils, this paper addresses the emissions and possible control of the three greenhouse gases by different managements of organic soils. More precise information is needed regarding the present trace gas fluxes from these soils, as well as predictions of future emissions under alternative management regimes, before any definite policies can be devised.

Notes: Abstract. The projected increase in sewage sludge used on land within many countries in the European Community will provide a major source of entry for several heavy metals into the soil. Although the application rate of sewage sludge to agricultural land is constrained by maximum annual additions of heavy metals, there is a need to know the sensitivity of those soils to heavy metal inputs which are physically suited for application. A rulebased classification using weighted parameters designed to assess the metal binding capacity of soil and the risk of groundwater pollution has been applied to soils data held within the Macaulay Land Use Research Institute's National Soils Inventory The classification uses soil pH, organic matter content, texture and soil colour as a surrogate for iron oxide concentration. The results indicate that some metals, for example cadmium and zinc are potentially more mobile in soils than others such as lead, but that the majority of soils display a strong or very strong binding capacity for all the metals. However this pattern can only be sustained if the soil pH values are maintained at their present values; a fall of one pH unit marks a dramatic shift towards the weak and moderate binding classes. The approach is largely unvalidated but does provide a useful framework for incorporating our mechanistic understanding of processes into wide area soil quality assessments and in identifying future research opportunities.

Notes: Abstract. Kriging is used to provide detailed quantitative information for a range of soil characteristics across the floodplain of the River Gambia. Application of spatial statistics to a large area with a coarse grid of data points produces spurious patterns unless the area is first partitioned into soil-geomorphic mapping units, each of which has a unique pattern of spatial variation. Even combining classical soil survey method with spatial statistics, the large short-range variability of acid sulphate soils means that single factor maps conceal a large element of uncertainty. A more robust procedure is to map the probability of occurrence of critical values of key characteristics.

Notes: Abstract. Field experiments undertaken at 14 sites, on a range of soil types, in lowland England, during the cropping years 1989–1993, tested the effectiveness of cattle or pig slurry as a source of nitrogen for cereal cropping. Slurry was applied in autumn, winter and spring, to autumn and spring sown cereal crops. Assessments included slurry nitrogen efficiency relative to N in spring applied fertilizer in terms of both grain yield and grain protein production, apparent crop recovery and content of mineral nitrogen in soil profiles. Crop response to nitrogen was poor at seven sites where high residues of soil mineral nitrogen (SMN) were present. On the seven responsive sites, spring slurry applications proved more efficient (mean 40%) as a source of N than autumn (mean 24%) or winter applications (mean 32%). These differences were smaller than reported in a number of other studies, probably as a result of relatively low excess winter rainfall, resulting in less nitrate leaching during the period of the investigation. Rapid incorporation into the topsoil of slurry applied in autumn, increased (28 kgN/ha) the SMN of samples taken early in the winter. However this increase did not lead to a consistent improvement in crop N uptake. Slurry dressings, whenever applied, can be expected to make a significant contribution to the N requirement of the succeeding crop and need to be taken into account when calculating the appropriate spring fertilizer application.

Notes: Abstract. Soils in areas with high livestock density contribute to the eutrophication of aquatic ecosystems through loss of nutrients, especially phosphorus (P). In order to identify the potential for P loss from such soils we determined phosphorus extracted by water (H2O-P), by double lactate (DL-P), and P sorption capacity (PSC) and degree of P saturation (DPS) in soil samples from two counties, one with low (Harle-catchment) and the other with very high livestock density (Vechta). Both catchments are hydrologically connected with the tidal areas of the North Sea.The mean concentrations of H2O-P (0.4mmol/kg) and DL-P (3.9 mmol/kg) were lower in the Harle-catchment than in the Vechta area (1.2 mmol/kg, 6.8mmol/kg). Although oxalate-extractable Al (Alox) and Fe (Feox) and the derived PSCs varied according to soil type and to land use, the livestock density and the resulting high concentrations of oxalate-extractable P (Pox) were shown to be the main reason for the very high DPS of up to 179% in the county of Vechta. These values exceeded DPS reported from other intensive pig feeding areas in western Europe and indicate the potential for significant P loss. Less than 40% of the variation in Pox could be explained by the routinely determined H2O-Por DL-P. Geostatistical analyses indicated that the spatial variability of Pox depended on manurial history of fields and Alox, showed still smaller-scale variability. These were the major constraints for regional assessments of P losses and eutrophication risk from agricultural soils using available soil P-test values, digital maps and geostatistical methods.

Notes: Abstract. Although gypsiferous soils cover approximately 100 million ha in the world, it is only in the past two decades that their pedogenic and agronomic properties have been better understood and their classification improved. There is still no method to assess adequately their production potential.This paper focuses on gypsum accumulation forms as diagnostic criteria for a rapid soil suitability appraisal in the field. Pseudomycelia, gypsum spots, powdery coatings and other localized in situ precipitations usually indicate soils with less than 15% gypsum. Depending on their intensity and depth of occurrence in the root zone, they define a soil environment which is suitable for semi-sensitive and semi-tolerant crops. Continuous gypsum accumulations characterize soils or horizons with high (e.g. more than 25%) gypsum contents, and these can be used only for tolerant crops.The land use potential of gypsiferous soils is primarily determined by: (a) the depth of the impermeable layer, (b)the gypsum content within the root zone, and (c) the crop tolerance level. A method is proposed to assess the land suitability of gypsiferous soils on the basis of these criteria.

Notes: A standardized dataset of derived soil properties for the 106 soil units considered on FAO-UNESCO's 1:5 million scale Soil Map of the World is presented. It was derived from a statistical analysis of the 4353 soil profiles held in the WISE (World Inventory of Soil Emission) database, which was developed at the International Soil Reference and Information Centre (ISRIC) for the geographic quantification of soil factors that control processes of global change. Median values are presented by soil unit for selected soil properties including: pH(H2O); organic carbon content; cation exchange capacity; sum of exchangeable Ca2+, Mg2+ and K+; exchangeable sodium percentage; bulk density; total porosity; available water capacity; soil drainage class; and gravel content class. Medians for these variables are presented both for the topsoil (0–30 cm) and subsoil (30–100 cm), where applicable. The data set can help to refine ratings for soil quality in global environmental models pending the availability of comprehensive georeferenced databases on soil and terrain resources such as SOTER, the World Soil and Terrain Database. In a Geographical Information System (GIS) it can be linked to the units shown on the digital Soil Map of the World through the legend code.

Notes: Abstract. The effect of grazing pressure on infiltration, runoff, and soil loss was studied on a natural pasture during the rainy season of 1995 in the Ethiopian highlands. The study was conducted at two sites with 0–4% and 4–8% slopes at the International Livestock Research Institute (ILRI) Debre Zeit research station, 50 km south of Addis Ababa. The grazing regimes were: light grazing stocked at 0.6 animal-unit-months (AUM)/ha; moderate grazing stocked at 1.8 AUM/ha; heavy grazing stocked at 3.0 AUM/ha; very heavy grazing stocked at 4.2 AUM/ha; very heavy grazing on ploughed soil stocked at 4.2 AUM/ha; and a control with no grazing. Heavy to very heavy grazing pressure significantly reduced biomass amounts, ground vegetative cover, increased surface runoff and soil loss, and reduced infiltrability of the soil. Reduction in infiltration rates was greater on soils which had been ploughed and exposed to very heavy trampling. It was observed that, for the same % vegetative cover, more soil loss occurred from plots on steep than gentle slopes, and that gentle slopes could withstand more grazing pressure without seriously affecting the ground biomass regeneration compared to steeper slopes. Thus, there is a need for developing ‘slope-specific’ grazing management schedules particularly in the highland ecozones rather than making blanket recommendations for all slopes. More research is needed to quantify annual biophysical changes in order to assess cumulative long-term effects of grazing and trampling on vegetation, soil, and hydrology of grazing lands. Modelling such effects is essential for land use planning in this fragile highland environment.

Notes: Abstract. An effective fertilizer recommendation system requires information on seasonal, soil-related and cultural variations in soil mineral nitrogen (N) and nutrient requirements of the crop. This can be provided by dynamic N turnover models, such as listed by Plentinger & Penning De Vries (1996). In this paper, we describe a survey of farmer opinion designed to ascertain what farmers want from such a decision support system. Over 100 farmers were surveyed. Surveyed farmers requested that default values be available for all model inputs. Inputs should be entered both by windows-based menu (for clarity) and tabular format (for speed), have user-selected units, and be fully supported by context-sensitive help. The system should have a hierarchical structure allowing access to fixed parameters, and be compatible with commonly used farm recording packages. Recommendations should be provided both for the field (single and optional application rates), and in tabular format across the whole farm. Simulations should be easily rerun using more recent crop and weather data. Turnover processes underlying recommendations should be illustrated by flow diagrams of flux between pools, pie charts of fertilizer fate, bar charts of movement down the soil profile and graphical plots of changes in N status against time.

Notes: Abstract. Ten chalk topsoils (0-25 cm) were repacked into columns in the laboratory. After leaching similar to one year's throughflow in the field, loss of K was equivalent to between 9 and 74kg K/ha. This represented between 3 and 30% of the initial exchangeable K with which loss was poorly correlated. Loss was dependant on the soil solution concentration and was inversely proportional to potassium buffer power.The loss of magnesium in the same columns was between 10 and 22 kg Mg/ha (6-21% of the initial exchangeable Mg). Magnesium loss was poorly correlated with exchangeable Mg.When KCl fertilizer was incorporated into the soils, the increase in leaching of potassium was 1–35% of the K addition. Application to the top of the column resulted in less leaching than when the K was incorporated. Leaching of magnesium was increased by up to 5 kg Mg/ha.Potassium leaching may be delayed by the underlying A/C horizon but pure chalk, with an extremely low buffer power for K, has little ability to retain K. Extremely calcareous topsoils were the most leaky although in practice it is the organic chalk soils on which it is most difficult to attain adequate K levels. On all chalk soils, maintenance of a high K level with K fertilizer is likely to cause unnecessary long-term leaching losses. Annual, rather than biennial, fertilizer applications are to be preferred.

Notes: Abstract. The effects of straw disposal by burning and incorporation on soil and crop nitrogen (N) supply, were investigated on two light textured soils in central (ADAS Gleadthorpe) and eastern England (Morley Research Centre) over the period 1984 to 1995. Nitrogen balance calculations showed that after 11 years of contrasting straw incorporation versus burn treatments, the cumulative N returns in straw were c. 570kg/ha at Gleadthorpe and c. 330 kg/ha at Morley However, these N returns via straw incorporation were not reflected in increased total soil N levels in autumn 1994. There were no differences (P 〉 0.05) between straw disposal treatments in autumn soil mineral N supply, readily mineralizable N or organic carbon. Similarly, there were no consistent differences between the treatments in terms of crop yield, crop N uptake or optimum fertilizer N rates. Fertilizer N applications of 200 kg N/ha/y increased topsoil organic carbon from 1.18 to 1.28% and total N content from 0.091 to 0.102% on the loamy sand textured soil at ADAS Gleadthorpe, but not at Morley. Previous fertilizer N applications increased the quantity of nitrate-N leached in drainage water by c. 20 kg/ha at Gleadthorpe and c. 60 kg/ha at Morley overwinter 1994/95, and by 10–20 kg/ha at both sites overwinter 1995/96. There was some indication overwinter 1994/95 that straw incorporation reduced nitrate-N leaching by 10–25 kg/ha, but there were no differences between treatments overwinter 1995/96.

Notes: Abstract. Formulation of nitrogen balances on farms requires accurate information on all inputs of the nutrient. N2-fixation by legumes, particularly forage legumes, is an important input which is difficult to measure. Simple regression models have been established from the literature for predicting N2-fixation by grass–white clover (Trifolium repens) mixtures using dry matter yields.Linear relationships were obtained between the N2- fixation (Nfix) and the extra dry matter production of mixed swards (Md) compared with pure grass swards. Nitrogen fixation was given by Nfix= A + 0.067Md where A is the intercept having a value of 6.8 for cut swards and -168.1 for grazed swards. A common slope was adopted because the F statistics showed that slopes fitted separately were not significantly different. The value of the negative intercept represents the supply of N to the grazed sward from soil and excreta-derived N. The regression equation for the cut sward gave reasonable predictions (r2= 0.953) of values of N2-fixed for experimental data not used in establishing the relationship. For grazed grass, the approach over-estimated the N2- fixation by an average of 15%.

Notes: Book reviewed in this article: Agricultural Recycling of Sewage Sludge and the Environment By S. R. Smith.

Notes: Book reviewed in this article: No-tillage seeding: science and practice By C. J. Baker, K. E. Saxton & W. R. Ritchie.

Notes: Abstract. The rates of CO2 production and decomposition of 13C-enriched Lolium perenne leaves and roots in soil from the surface five cm of two upland stagnohumic gley soils were measured in laboratory experiments. One of the soils had been limed (pH 6.8) 13 years earlier. The other was unlimed (pH 3.7). Liming increased the rate of CO2 release from soil to which no L. perenne had been added. About 30% of the 13C in L. perenne leaves remained in both limed and unlimed soil after 224 days. By contrast, less 13C-remained in the limed soil amended with L. perenne roots (44%) than in the limed soils (55%). Although the daily rate of CO2 from the plant material-amended soils was initially greater in the improved than in the unimproved soil, it subsequently declined more rapidly.

Notes: Abstract. The characteristics and variability of soils within a 30 ha experimental site in N. E. Nigeria are analysed in relation to tree establishment. Profile description and analyses for some 480 surface samples of the sandy to clayey surface soils from Lake Chad lacustrine sediments provide baseline properties against which any subsequent modifications resulting from agroforestry practices can be assessed and to which initial tree performance can be related. This has been undertaken using principal component and spatial analyses. Inherited soil properties show spatial variations across the site which can be related to the soil textural parameters. The initial survival of trees planted for agroforestry experimentation shows strong correlations with the inherited characteristics of the soil rather than with acquired soil properties.

Notes: Abstract. Field measurements of cumulative infiltration and of the matric potential prior to infiltration were made with double-ring infiltrometers and tensiometers, respectively, on two sandy loams in north-east Scotland. The time to ponding for constant-rate infiltration was also measured in the same infiltrometers by applying water at a constant rate until ponding commenced. Under the range of initial potentials studied (-2 to - 17 kPa), an exponential relation was adequate to describe the relation between sorptivity and initial matric potential. The time to ponding was also strongly dependent on initial matric potential and increased dramatically as the soil became drier. Measurements of time to ponding were in good agreement with values predicted from the theory of Clothier et al. (1981) using values for sorptivity and the A parameter obtained from the cumulative infiltration experiments. Measurements and predictions clearly showed the importance of the sorptivity versus initial matric potential relation in controlling the time to ponding of such sandy soils. These results have implications for determining the generation of runoff and the establishment of stream flows, as well as determining optimum rates and design of irrigation.

Notes: Abstract. Use of either three or six occasions to spread similar total amounts of slurry was investigated over the late winter/early spring period in two years, on plots with underdrainage. Slurry was spread on four 7 m by 25 m plots which were instrumented to allow collection of drainflow and runoff. The ‘mobile water’ pore space allowed transport of a small proportion of applied slurry through the 0.75 m soil profile. Evidence of a polluted ‘mobile water’ pulse occurred after periods of up to 48 hours following spreading, suggesting subsurface rather than overland flow. Timing of the pulse depended on whether subsequent rainfall accelerated the flow The contaminated flow persisted for 6–12 hours. The worst contamination of 39 mg/l NH4+ -N occurred under ‘bypass flow’ conditions, when 52 mm of rain fell during the 48 hours after a 5.2 mm application. Two contributory factors appeared important. The first was the long duration of the high intensity storm and the second was an extended period of severe frost believed to have created fissures associated with frost heave. Making several applications of slurry in amounts less than 35 m3/ha is preferable to fewer larger applications during spring, for cereals on medium to heavy soils. This recognises the likelihood of there being underdrainage on arable land and the optimal use of well-drained, partially frozen ground to avoid compaction by slurry tankers.

Notes: Abstract. When Albania emerged from its seclusion in 1991, the scientific community had its first opportunity to interact with its international counterparts. Soil resource assessment was made with systems developed in the early 1950s, laboratory facilities to provide supporting data were poor, and it was recognized that a new assessment was urgently needed.The country faces a major challenge in reforestation and soil conservation against a background of overgrazing by sheep and goats and clearing of trees and scrubs for fuelwood. Even orchard and olive trees were used as fuelwood during the winters of 1990 and 1991. Since then, gully and rill erosion has accelerated on many of the sloping lands. In addition to reforestation and conservation measures to reduce the pressures on the sloping land, it is necessary to enhance productivity on the fertile valley bottom soils where most of the agriculture is confined. In the recent past, grain yields have declined due to reduced fertilizer use (low purchasing capacity), and poor management practices. More recently productivity has slowly improved, but land degradation, particularly erosion, has visibly increased.USDA Natural Resources Conservation Service in collaboration with the Land Resources Institute of Albania, initiated work on a new national soil map through collation of existing information and field studies. The land unit for land use planning, evaluation, and general management decisions, is the Major Land Resource Area (MLRA). Each MLRA encompasses geographically associated soils, the majority of which have broadly similar patterns ofclimate, water resources, and land uses. The MLRAs presented here are based on the soil map of Albania at 1 : 200 000 scale. The MLRA information provides an overview of the landscape and natural resources. It can be used to assess land suitability for various crops, opportunities to achieve self sufficiency in food production, selection of areas for both field crops and highvalue crops for export, and identification of appropriate farming system technologies. Each MLRA will have a set of degradation processes which can be flagged, therefore each of them becomes a unit for decision making with respect to investments in research and mitigating technologies. The task is far from complete. Appropriate databases are needed to support the decisions that are being made at national level. To complement the MLRA and related database, decision support systems are needed for the important task of developing policy options.

Notes: The binding of metal to humic substances is problematical. The approaches for studying metal binding to organic matter are briefly reviewed. Ion-selective electrodes (Cu2+ and Pb2+) were used to measure metal complexation by a whole peat and an extracted humic acid (HA) fraction. Scatchard plots and calculation of incremental formation constants were used to obtain values for the binding constants for the metals onto both peat and HA. Both the peat and the humic acid had a larger maximum binding capacity for Pb2+ than for Cu2+ (e.g. at pH = 5 HA gave 0·188 mmol Cu2+ g−1 and 0·564 mmol Pb2+ g−1: peat gave 0·111 mmol Cu2+ g−1 and 0·391 mmol Pb2+ g−1). Overall, the humic acid had a larger metal binding capacity, suggesting that extraction caused conformational or chemical changes. The binding constants (K1) for Cu2+ increased with increasing pH in both peat and humic acid, and were larger in the peat at any given pH (e.g. at pH = 5 HA gave log K1= 2·63, and peat gave log K1= 4·47 for Cu2+). The values for Pb2+ showed little change with pH or between peat and humic acid (e.g. at pH = 5 HA gave log K1= 3·03 and peat gave log K1= 3·00 for Pb2+). In the peat, Cu2+ may be more able to bind in a 2:1 stoichiometric arrangement, resulting in greater stability but smaller binding capacity, whereas Pb2+ binds predominantly in a 1:1 arrangement, with more metal being bound less strongly. Whole peat is considered to be more appropriate than an extracted humic acid fraction for the study of heavy metal binding in organic soils, as this is the material with which metals introduced into an organic soil would interact under natural conditions.

Notes: Excess salts may be removed from soil by leaching, but ponding water on the soil's surface and allowing infiltration requires large quantities of water. During such leaching water flows preferentially through macropores between aggregates, while the flow within aggregates is much less. Consequently, solute within aggregates is removed much more slowly, thus decreasing overall leaching efficiency. For this reason intermittent ponding can be more efficient because it allows time for solute to diffuse to the surfaces of aggregates during the rest period and subsequently be removed in macropore flow. We explored solute transport in aggregated soils under intermittent leaching in three ways: theoretically, by laboratory experiments on columns of porous ceramic spheres as analogues of aggregates, and by simulation. Solute movement during displacement is described by the mobile-immobile convection-dispersion equation. During the rest period flow ceases, and solute redistributes within the aggregates by diffusion, the key variable being the effective diffusion coefficient, De of the solute in the aggregates, and longitudinally by diffusion within macropores (though this was ignored in the simulation). We estimated De for our porous spheres from observations of solute outflow into finite volumes of stirred distilled water. The theory was validated against experiments on saturated columns for different aggregate-size distributions, flow velocities, and displacement and rest periods, with most parameters estimated independently. Experiments and simulations showed that water savings of 25% were possible under our laboratory conditions, increasing as aggregate size, flow velocity and duration of rest period increased. The potential of intermittent leaching in the field is considered.

Notes: Comparisons were made between the phenolic and carbohydrate signatures of soil profiles developed under grass, spruce and ash stands. Samples were collected from a brown earth soil which was originally under the same land use, but over the past 43 years has supported different monocultures. Distinct signatures associated with each litter type were recorded in individual profiles. A relatively undecomposed phenolic fraction from lignin and hydrolysable carbohydrate fraction from plants had accumulated in the soils under spruce and ash. This largely reflected the quantity and quality of the litter inputs from the spruce and ash compared with the grass. The phenolic and hydrolysable carbohydrate fractions accounted for as much as 60% of the total organic carbon concentration in the deep horizons. In the grassland profile both fractions were more decomposed than under ash and spruce suggesting that the forest profiles had rapidly accumulated a carbon pool with a comparatively slow rate of decomposition. This was most apparent from the spruce profile (which contained 398 mg g−1 C carbohydrate hydrolysed using trifluoracetic acid (TFA) in the C horizon compared with 165 and 45 mg g−1 C under ash and grass respectively). We conclude that the decay rate of these fractions is a function of the vegetation type.

Notes: Fractal dimensions were used to quantify the complex geometry of soil cracking patterns. Two fractal dimensions were measured to provide an adequate description of soil cracks: the mass fractal dimension, DM (which provides a measure of crack heterogeneity) and the spectral dimension, d (which provides a measure of crack connectivity). The cracking patterns generated by four soils were compared and related to their textural characteristics. As the clay content of the soil increased (6·1%–24·3%), so did DM (1·29–1·43), and d (1·03–1·33). Correlations indicated that there was a significant (P 〈 0·01) linear relation between the soil's clay content and the DM and d of cracks, the correlation coefficients obtained being equal to 0·965 and 0·840, respectively. Significant correlations (P 〈 0·01) were also observed between structural stability indices of the soil and the fractal dimensions of its cracks, increases in the stability of the soil, particularly of the clay fraction, being associated with cracks with greater fractal dimensions.

Notes: The relation between physical and mechanical responses and the structure of clay has been studied. Deformation in response to mechanical stress was measured on samples of Wyoming mont-morillonite and Saint Austell kaolinite in solutions of NaCl (0·005; 0·05; 0·5 and 5 M). Salt concentration was expressed in terms of osmotic potential of water and loading in terms of envelope pressure potential of water, and deformation was measured precisely under small mechanical stress. During shrinking and swelling, deformation was small and reversible, and consolidation was related to the largest mechanical stress applied previously in its history. The arrangement of the clay at equilibrium depends foremost on the type of clay mineral and physico-chemical properties of the liquid phase. For Na-montmorillonite suspensions, transition between gels with tactoids and rigid media with quasicrystals is abrupt and occurs at a potential of about −2000 J kg−1, whether the stress is osmotic or mechanical. Swelling indexes obtained under osmotic and mechanical stress are of the same order of magnitude. Deformation of smectite results from modifications of interassemblage and intra-assemblage organization.

Notes: We have developed a critical state, stress-strain analysis that predicts the entire sequence of states from start to the end of a constant cell volume triaxial test in p-q-v-ɛz, space, where p is the spherical stress, q is the deviator stress, v is the specific volume and ɛz is the axial strain. The analysis requires five soil properties to be specified, these being the critical state properties (M, λ and κ) and two elastic properties (any two of E, η, G and K—all four can be found from any two).In order to test the analysis, properties taken mostly from one series of constant cell volume triaxial tests are used to simulate the behaviour in a second test series. In both series the two soils (a sand loam and a clay loam) were tested at several different water contents. The first (property estimation) series of tests was performed using large samples, whereas the second (verification) series involved small samples. The behaviour is quite different in the two series. The elastic property E was not determined in the first series of tests but was estimated from the second series. Furthermore, for three very wet samples, λ had to be estimated by fitting the analysis to the data. The verification was not therefore fully independent of the input test data, particularly for the three wet samples. The stress strain analysis simulated the behaviour of both series of tests in all four dimensions of the p-q-v-ɛz space. The match in p-q-v space was good for all samples. On a q-ɛz plane, the value of q was under-estimated for several samples, but for most of the samples the match was good on this plane. The analysis was generally as good as, and sometimes better than, a previous analysis that deals only with the end point of the test in p-q-v space. The previous analysis did not take account of the elastic properties. The stress-strain analysis therefore seems to offer a useful framework for parameter estimation from constant cell volume triaxial tests. This extends the usefulness of the test itself, as the elastic properties may now be accounted for. The success of the analysis also strengthens the record of success of the critical state concept for unsaturated soils.

Notes: Measurements of N uptake by rice plants growing in a puddled flooded soil and the corresponding changes in soil solution NH: concentrations and the soil NH: diffusion coefficient are used to calculate how far root uptake properties and transport to the roots limit acquisition of N by rice. With root uptake parameters assigned values such that influx was maximal within realistic ranges, the minimum root length densities required to explain uptake were similar to measured root length densities in both N-fertilized and unfertilized soil. This suggests that most if not all of the root length was active in uptake and that uptake per unit root length was near maximal. A sensitivity analysis showed that the necessary minimum root length is very sensitive to root uptake properties within appropriate ranges. Transport to the roots was mainly by diffusion. Rates of diffusion will generally not limit uptake in well-puddled soils, but they may greatly limit uptake in puddled soils that have been drained and re-flooded and in unpuddled flooded soils. Uptake of fertilizer N broadcast into rice field floodwater and absorbed by roots in the floodwater or soil near the floodwater is not likely to be limited by root uptake properties or transport.

Notes: The derivation of pore size distributions from the soil water retention characteristic is complicated by the influence of the connectivity of the pore space on drainage. We examine this issue in the context of a random fractal pore network model. A two-dimensional one-parameter model simulates the drainage of water from an initially saturated pore network, explicitly accounting for the complex pore interactions which exist over a range of scales within the network. A parameter range is identified over which pore connections significantly hinder the advance of air into the network. The results demonstrate that connectivity between pores in a random structure can affect the drainage to an extent that in general it is not possible to obtain an accurate measure of the pore size distribution from the water retention data. These results, together with findings based on closely related multiscale network models, show that one should use with caution water retention models derived from fractal structures and based solely on pore size distributions.

Notes: The recent addition of trivalent metals to soil and their subsequent movement within the biosphere are of concern. For this reason, the sorption of chromium (Cr), yttrium (Y). rhodium (Rh), lanthanum (La), praseodymium (Pr) and gadolinium (Gd) in two contrasting acid soils has been determined. Except for Rh, the sorption of the other trivalent metals conformed well to the Langmuir equation with derived sorption parameters similar for all the trivalent species tested. Calculation of the buffer powers indicated that under both small (0·01 mmol kg−1) and large (1 mmol kg−1) trivalent metal soil loadings 〉 99·5% of the metals will be associated with the exchange phase with small quantities present in the bulk soil solution (〈0·5%). It seems that the slight availability of metals within the bulk soil solution will slow the rate of trivalent metal bioremediation of contaminated sites.

Notes: Compositional differences between soil solutions obtained by different methods have frequently been reported; variations in the soi1: solution ratio may explain these results. In this study we compared the amount and composition of phosphorus (P) in soil leachates and soil solutions from a temperate grassland soil in northeast Scotland and determined the influence of soi1:solution ratio on P fractions in soil water extracts. Leachates were collected from intact soil cores over 6 months, the cores were then destructively sampled, and soil solutions obtained by centrifuging. Molybdate reactive P (MRP) represented 71% of the total dissolved P (TDP) in soil leachates but only 54% in soil solutions. The MRP component in soil water extracts increased from 71% to 92% as the soi1:solution ratio increased from 1:15 to 1:15·4, while the dissolved organic P (DOP) component decreased from 26% to 6%. As the soil:solution ratio increased the amount of MRP extracted increased; by contrast the amount of DOP and dissolved condensed P (DCP) extracted remained constant. While the MRP component is regulated by soil sorption processes, the supply and amount of DOP and DCP is probably related to biological activity. Dissolved organic carbon (DOC) extracted at wide soi1:solution ratios contained a smaller proportion of P than that extracted at narrower ratios. The results indicate differences in the behaviour of P fractions in the soil at various soi1:solution ratios and that these are reflected in the P composition of soil solution and leachate.

Notes: In a pre-alpine meadow in the Toggenburg (Switzerland), casts of the earthworm Aporrectodea nocturna, initially detected 20 years ago around a newly planted hedge, now extend 170 m from the hedge. The abundance of A. nocturma decreased between 140 and 170 m from the hedge from 237 (site: An+) to 0 (site: An−) individuals m−2. The worm's activity and the macroporosity it has created have been studied using CAT scanning followed by automated image analysis of pores from 1·5 to 9 mm diameter. Brightness values in images from CAT scanning showed distinct local frequency maxima for stones, soil matrix and macropores. Measured diameters of pores were strongly linearly correlated with diameters of needles used to produce artificial pores. Pores from 1·5 to 3 mm were most abundant. The maximum number of pores from 1·5 to 9 mm (about 1600 m−2) was larger than the maximum number of all earthworms (about 480 m−2). Modelling the cast production of A. nocturna indicated that 23·8 kg m−2 were deposited on the soil's surface within 3 months. The measured macroporosity (1·5–6 mm) was one-quarter to one-sixth of the pore volume corresponding to the removed casts. Thus, net production of pores by earthworms was a result both of the burrowing activity and of the refilling with eroded cast material. Depth distributions of bulk density, total porosity and pores from 1·5 to 9 mm were different at An+ from those at An−. However, diffusion of butane was equal at An+ and An−. Three-dimensional reconstruction suggested that the disposition (continuity, interconnectivity) of pores was more important for gas diffusion than the structure (size distribution, frequency) and bulk soil parameters.