摘要:

SummaryThe variable soils of the recent alluvium of parts of Iraq contain horizons falling into two groups, viz. bad‐structured horizons which are hard and dense with marked vertical cracking, and well‐structured horizons characterized by a friable consistency and higher porosity. Gilgai occurs as the extreme bad‐structured phase. The only constant difference in laboratory data between these groups is the low laboratory permeability in the bad‐structured horizons. These features cannot be explained using the causes so far put forward for gilgaied soils in Australia, but they suggest an explanation of the process of formation of bad structure (in the agricultural sense) in terms of compaction by weathering agents. It is suggested as being a process which is habitually taking part in the development of solonetz soils, since the latter always seem to be characterized by this bad st

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01909.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryThe formation of podzols with well‐marked iron pans on boulder clay soils overlying chalk is described. A sub‐peat soil at Goodland is to be regarded as a fossil soil with two podzol profiles superimposed. The upper podzol formed in a relatively short time prior to the growth of the overlying blanket bog following tillage which helped to accelerate the rate at which podzolization occurred. A well‐marked iron pan in a podzol at Torr has developed during the past hundred years. The formation of an impermeable humuslayer within the top few inches of such soils leads to waterlogged conditions suitable for the development of blanket bog over them. This humus layer effectively seals the underlying podzol from waterlogged or gleying conditions.Accepting the hypothesis that the podzol at Goodland is a fossil soil, a chronology for soil development is proposed using archaeological material as dating evi

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01910.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryIn archaeological sites of Pleistocene and Postglacial age fossil soil horizons may be buried or form part of a composite soil profile when they may be either degraded or relic in nature. Since the A horizons of soils may be identified by their humus forms and the B horizon by their fabrics, both immature and mature fossil soil horizons may be identified and distinguished from man‐made deposits such as occupation layers and ditch fillings. Thus, micromorphology can be used as a geochronological technique for supplementing the existing knowledge of the mild and cold phases of the Pleistocene and to a lesser extent of the Postglacial.In mature fossil soils, since the fabrics of many B horizons are characteristic of certain soil types and are not altered by colluvial activity, it is possible to deduce something of the physiographic environment under which such fossil soil horizons were formed and, in particular, of the climate at the time of their formation. Thus, from composite soil profiles in archeological sections, relic fabrics have been observed and the primary origin of such colluvially derived soil material deduced. From buried profiles in loess sections of Europe the occurrence of braunerde fabrics withsol‐lessivéfeatures confirms the other lines of evidence which suggest that the mild phases of the Pleistocene had similar climatic conditions and that these differ from those of today in the same area only in that the summers are today somewhat cooler and wee

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01911.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryThe chalk and associated superficial deposits of the Chiltern Hills give rise under beechwoods to a sequence of soils ranging from rendzina through brown earth (sol lessivé) to podzol, closely paralleled in developmental sequences established elsewhere on uniform calcareous materials. The salient features of the genetic soil types represented are described and their evolution discussed in relation to vegetation and site characteristics. On base‐deficient soils, mor formation under beech is conditioned by local climatic factors and management practices as well as by inherent fertility variations and is only associated with advanced podzolization on appreciably sandy materials. On silty plateau soils with imperfect drainage, ‘micro‐podzols’, which may be transitory, ar

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01912.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryFour profiles in the Mt. Burr forest area of south‐eastern South Australia have been examined in detail. Two profiles were podzolized deep aeolian sands overlying buried soils which had developed on basaltic tuff, a third profile was developed on olivine basalt while the fourth was a composite profile developed on basaltic tuff and containing a buried profile formed on an earlier ash shower.The main factors operative in influencing the geochemical distribution of the elements in these profiles were the translocation of elements by plant growth and their relative mobility on weathering, association with the clay fraction, and restricted drainage. In the aeolian sands Ca, Mn, and V with lesser amounts of K, P, Mo, Cu, Mg, Zr, and Al, were the elements which generally accumulated in the surface horizon as the result of plant action. In the surface soils of volcanic origin Ca, Mn, P, and Mg with lesser amounts of Cu and K accumulated. The highest concentrations in the clay fraction were, in general, for the aeolian sands Al, Fe, Ga, V, and Ni, and in the basaltic soils Na, Al, Ga with, to a lesser extent, K, V, P, and Ni. In the soils developed on basaltic material the elements most readily lost from the weathering zones during soil formation were in decreasing order of magnitude, Ca, P>Na, Mg, Co, Zn>Cu, Mn>Ni. K, V, Ga, Mo, Fe, Al, Ti, and Zr were in general much less mobile and tended t remain incorporated in the weathering products and concentrated in the upper weathering zones. P, Zn, and Cu and to a lesser extent Mn, Fe, Ni, Co, and Ca were found to be more readily lost on weathering under conditions of restricted drainage.The elements most concentrated in the hardpan of a ground‐water podzol were, in decreasing order of magnitude, Fe>Al ≫ V, Zn, Ni>P, K, Mo>Na, Mn, Cu, and Ti. When the more strongly cemented nodules were separated for analysis it was found that relative to the matrix Fe>Al, V, and P, in that order, were most concentrated. Zn alone was lower in the nodules than the sandy matrix. Mn and Mo were most concentrated in the upper part of the hardpan, and Zn, V, Ni, Cu, Ti, and P in the lower part.Some of the mineralogical changes which have taken place during the weathering of the basaltic material have been studied by examination of sand and clay fractions of the soil and thin rock sections. In the olivine basalt, the plagioclase and, to a lesser extent, olivine have weathered most readily. The main weathering products of the soil developed on the olivine basalt were kaolin and haematite. In the tuff the first important weathering product was montmorillonite, formed by the breakdown of the volcanic glass. This montmorillonite was found to break down in the upper weathering zones of the soils formed on tuff to give kaolin and goe

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01913.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryThe clay mineralogy of Australian red‐brown earths has been investigated by X‐ray diffraction techniques supported by chemical analyses.A brief description of the morphology of this group of soils is given, and their geographical distribution indicated. Profiles have been studied from each of the major areas in which red‐brown earths are found.A large number of samples were examined by X‐ray diffraction. The results showed relatively little variation in clay mineralogy from one profile to another, or from one horizon to another within a profile. The dominant clay minerals in typical red‐brown earths in southern Australia are illite and kaolin, but in Queensland kaolin predominates.Chemical data (cation‐exchange capacity, SiO2: Al203ratio) are consistent with the X‐ray results. There is evidence, however, that the illites in these soils are deficient in structural potassium, having K contents between 2.5 and 4.1 percent. K approximately. There is a consequent increase in the exchange capacity of these‘degraded’ illites.The variations in the clay mineralogy of these soils appear to depend mainly on the parent materials from which the soils are derived. Those red‐brown earths developed on alluvial and similar materials contain more illite than kaolin; those soils developed on materials such as granite, granodiorite, and basalt contain mainly kaolin i

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01914.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryWet sieving as a measure of the effect of leys on crumb stability is discussed, briefly nothing the significant details of sampling and analysis.The increase in water‐stable aggregation following several ryegrass/white clover leys of four years duration was of the same magnitude for both clay and sandy loam soils. The lighter soil, having the lower initial stability, showed the greater proportionate increase. Perennial rycgrass/white clover swards were consistent in giving higher values for water‐stable aggregation than other commonly sown grasses. It would seem that a large proportion of clover in a sward would not impair the stabilizing effect of a ley. There was no evidence of any significant variation resulting from different methods of grassland utilization. Data from Hurley soil suggest that intensive grazing did not reduce the effect of the grass ley on soil stability as long as a plant cover was maintained. Cocksfoot sown in drills for seed production had less effect on the soil than did swards of this grass sown with white clover. The application of nitro‐chalk to grass leys over a three year period at annual rates up to 16 cwt. per acre had no significant effect on either of the soils examined. Profiles to 1 ft. depth showed that, whereas the high stability found under permanent pasture extended throughout this profile, the increase in water‐stable aggregation under a three‐year ley was largely confined to the top few ce

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01915.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummarySeasonal fluctuations in organic nitrogen and nitrate nitrogen in the soil of the Sudan Gezira are described under conditions of extended fallowing in cotton rotations. Statistically, results show that soil organic nitrogen is independent of rotational phase. Cotton yields are not limited by the content of organic nitrogen in the soil, but by soil physical conditions which improve by extended fallowing. Evidence is presented to show that soil organic nitrogen and nitrate nitrogen in this soil do not function in close interdependence. This conclusion was drawn in other work previously published.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01916.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryThe seasonal variation in the organic‐carbon content of Gezira soil under irrigated rotational cropping has been studied over three successive years. Emphasis has been placed on the cotton phases of the rotations. Significant differences in organic carbon occuring between rotations did not produce differences in degrees of nitrogen fixtion. It is suggested that fixation and mineralization of nitrogen occur so rapidly in this soil that it is not possible by chemical analysis to determine the amount of nitrogen fixed.Seasonal changes in organic‐carbon content display a phase of slow fluctuation when the soil is wet and carries a crop, and a phase of rapid fluctuation when the soil is bare, dried by insolation, and cracked. Attention is drawn to this phase and to the need for better understanding of the associated phenomena which contribute to the maintenance of high fertility in these arid so

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01917.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SummaryThe seasonal fluctuations and rotational differences in carbon‐nitrogen ratios are reported under irrigated rotational cropping in the Sudan Gezira. Statistical analysis shows that there are no rotational differences in carbon‐nitrogen ratios.Seasonal fluctuations in the ratio reflect the cropping period in the rotation and also display marked activity during the period of the year when it is very hot and

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1958.tb01918.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY