Showing papers in "European Journal of Soil Science in 1958"

A relation between permeability and size distribution of pores

Abstract: Summary An equation has been derived for the relation between permeability and the size distribution of the pores in isotropic material. If the mean radius of the pores in each of n equal fractions of the total pore space is represented in decreasing order of size by r1, r2., and rn cm. respectively, then permeability is given by where is the porosity in cm.3/cm.2 of porous material, and K is in units of cm.2 By this means, permeability can be calculated from she curve relating water content to suction. This has been tested on published data for flow of air through porous stones and flow of water through saturated and unsaturated sands. Calculated values have been found to agree satisfactorily with measured values over a wide range of permeability. The Kozeny equation is discussed as a particular case of this equation

Identification of clay minerals from acid soils

Abstract: Summary A technique is described for the identification of clay minerals, the layers of which are difficult to expand or collapse by the usual treatment with glycerol and KCl. Samples are extracted for 3 to 6 hours in normal sodium citrate at pH 7–3 and 100° C. The citrate is renewed hourly. After the citrate extraction the inter- layer spaces of some minerals can be expanded with glycerol and CaCl2 Basal spacings of minerals previously identified as ‘dioctahedral vermiculite’ expand to 16–18 A. after this treatment; hence, their identity is questioned. The widespread occurrence in the north-eastem United States of clay minerals with 14-A. spacing necessitates this extraction for correct identification.

Soil phosphorus fractions in some representative soils1

Abstract: Summary The distribution of soil inorganic phosphorus in soils was found to measure the degree of chemical weathering, the chemical weathering sequence being calcium phosphate, aluminium phosphate, iron phosphate, and occluded phosphate. The latter category includes reductant soluble iron phosphate and aluminium-iron phosphate occluded in iron oxides. For example, three horizons of one Chernozem profile, a Dark Brown soil, and the calcareous C1 horizon of a Grey-Brown Podzolic soil containqd 68–95 per cent. of their inorganic phosphorus in the form of calcium phosphate, the other forms decreasing exponentially in the sequence. The inorganic phosphorus of two Latosols increased exponentially in the order calcium phosphate (1%), aluminium phosphate (0–3%), iron phosphate (10–13 %), and occluded (reductant soluble) phosphate (66–78%). Three samples of podzolized soils contained intermediate, sigmoidal distributions of the four phosphates. In two Miami silt loam profiles, the 0–002 N H2SO4-extractable-phosphorus test was much higher in the subsoils down to 31/2 ft. than in the surface soil, and was correlated mostly with the calcium-phosphate content, somewhat with aluminium and iron phosphate, and none at all with occluded phosphates which constituted a high percentage of the total phosphorus. The higher content of available phosphorus in the subsoils and release of phosphorus in the surface soil by de- crease of A1 and Fe activity through liming most probably explain the lack of crop response to added phosphate fertilizer even though the surface soil had a low phosphorus test. Application of phosphate fertilizer to Almena silt loam greatly increased the amount of aluminium and iron phosphate at three lime levels: only a slight increase of calcium phosphate occurred; at tge highest lime level. The amount of occluded phosphate remained unchanged by liming or fertilization. The relatively small increase of calcium phosphate through phosphate application is attributable partly to crop removal but is shown to be due mostly to formation of the less soluble iron and aluminium phosphates.

Chemical studies of podzolic illuvial horizons

Abstract: Summary Titration curves of humus suspensions (prepared from some representative podzol B horizons by acetylacetone extraction) in o.1 N KCL are Presented. The shape of each curve (in absence of added metal ions) and the apparent PK value (PKe) derived from it are affected by the amount of Al contained in the suspension. One soil extract (initial PH 3.6) had a C/Al ratio of 4.9 and gave PKe= 6.21, Whereas the amberlite-treated extract (initial PH 2.6) had a C/Al ratio of 152 and PKe= 4.12. Extrapolation of PKe values to zero concentration of Al gave limiting values of 4.o and 3.8 for the humus extracted from a Queensland and a New Zealand podzol respectively. These figures are lower than those normally quoted for humic acid, but they may be characteristic of the translocated humus of podzols. Titration curves of fresh humus extracts with added Al+++, Fe+++ or divalent transition metal ions did not suggest the presence of complex sites although the results for Fe+++ are uncertain owing to the complexity of the equilibria involved Similar titrations with added Al+++ and Cu++ using amberlite-treated extracts did not indicate potential complex sites and, as before, the Fe+++ data were inconclusive. By analogy with Cu++ it is unlikely that Fe complexes ate present in these systems. It is concluded that humus is immobilized in these horizons by elexctrostatic bonding with Al+++ (since free Fe+++ would not exist at the soil PH), and the residual Al contained in the organic micelles in suspension is probably also bound by Coulomb forces. It is pointed out that the approximate methods used in this study for practically metal-free preparations may not reveal the presence of the type of complexes found by other workers for some synthetic Polyelectrolytes.

Major genetic soils of the arctic slope of alaska1

Abstract: Summary The genetic soils of Arctic Alaska can be arranged in a drainage catena. The mature soils on well-drained sites are Arctic Brown and related soils. The Tundra profile is an imperfectly- to poorly-drained catenamember. The Bogs, with permafrost, occupy many of the broad, flat, very wet areas. No evidence of a qualitative soil-forming process unique to the Arctic areas is found. Instead, the Arctic Tundra is primarily a northern extension of the hydromorphic soils of the forested regions, whereas the Arctic Brown arid related soils represent the northern extensions of the podzolic process. The term Tundra, when used in connexion with zonal great soil groups along with Podzols, Chernozems, Laterites and related soils, is an erroneous one and its use, except for a hydromorphic soil, should be discouraged. The podzolic process on the stable, well-drained sites weakens northward, resulting in the successive development of Podzols, Minimal Podzols, Arctic Browns, Arctic Browns shallow phase, and, finally, no soil formation.

The alkaline nitrobenzene oxidation of soil organic matter

Abstract: Summary The yields of syringaldehyde, vanillin, and p-hydroxybenzaldehyde obtained by alkaline-nitrobenzene oxidation of soil organic matter indicate the extent to which lignin-derived material is present. A number of soils, peats, and peat fractions have been oxidized by this method and the phenolic aldehydes formed have been separated and determined by a- micro-technique. The results indicate the presence in soil organic matter of significant amounts of syringyl, guaiacyl, and p-hydroxyphenyl residues which are almost certainly derived from lignin. The yields of aldehydes from mineral soils accounted for about 0.5–1.0 per cent. of the total organic carbon; from peats for about 1.0–4.0 per cent. There was evidence of a correspondence between the relative amounts of the three aldehydes obtained from the soil organic matter and from the parent plant material. The results for a peat profile indicated a tendency for the yield of aldehydes to increase with depth of the horizon; the reverse was found with a pine-forest soil profile. Peat fractions all gave some aldehydes on oxidation, but there were marked differences in the levels; the highest yield, almost 7 per cent., was obtained from a humic-acid fraction soluble in ethanol-benzene. Hydrolysis of the humic-acid fractions with dilute hydrochloric acid markedly depressed the yields of aldehydes obtainable on oxidation.

The nature of the drain channel as a factor in the design of a land‐drainage system

Abstract: Summary Drainage theory is customarily discussed on the assumption that the drainage channel is uniformly permeable. In practice such channels often consist of short lengths of relatively impermeable pipe separated by gaps. It is shown here that the appropriate modification to the theory in order to embrace such channels is to substitute an equivalent permeable channel of smaller radius. Experiments described here enable one to evaluate the equivalent drain radius, and show that this radius is not solely dependent upon the geometry of the gappy channel but is markedly affected by the ratio of intensity of rainfall to soil hydraulic conductivity. In the examples shown a tenfold increase of rainfall rate causes a hundredfold increase of effective drain radius.

Some factors determining water-table heights in drained homogeneous soils

Abstract: Summary The effect of the depth of impermeable floor below the drain level on water table heights in homogeneous soils, drained by a uniform system of ideal drains, for steady state conditions with various rainfall intensities, was investigated by means of hydraulic model and electric analogue experiments. Agreement was obtained between the two series of experiments which indicated that, for a given ratio of rainfall intensity to hydraulic conductivity, the water-table height midway between the drains decreased as the depth of the impermeable floor below the drain was increased from zero, tending towards a constant height when the ratio of the depth of the impermeable floor below the axis of the drain tube to the half spacing of the drains approached 0.3. In addition, in the experiments with a deep impermeable floor, agreement was found with the analytically obtainable solution of the problem with an infinitely deep floor. Water-table heights observed in the non-steady state hydraulic experiments approximated to those of the steady state with uniform distributions of flux cutting the water table for corresponding equal mean distributions, calculated from the drain discharge.

The application of soil micromorphology to fossil soils and other deposits from archaeological sites

Abstract: Summary In 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 with sol-lessive features 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 weetter.

The geochemistry of basaltic materials and australia associated soils of south-eastern south australia

Abstract: Summary Four 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 goethite.

The classification of soils

Abstract: Summary There are two possible ways of ordering natural formations: (1) by simplification in order to save time and to make possible an easy grouping by forgoing detailed specification (ordering by one or by a limited number of definite properties); (2) by forgoing simplification and by giving full weight to detailed specification in the establishment of the systematic units, in order to make possible the application of the system in every branch of general and applied science that deals in some way or other with the natural formation to be defined and ordered (ordering by differential diagnosis with no restriction to number or kind of properties). Both the above systems of ordering are possible with soils. Both are justified, their respective application depending on aims, purposes, and necessities. They could neither fight nor help each other; they are divided from the very beginning by their different principles and goals which lead necessarily to two independent branches of soil systematics.

The gilgaied and bad-structured soils of central iraq

Abstract: Summary The 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 structure.

The effect of nitrogen additions on fertilizer‐phosphorus availability. ii1

Abstract: Summary A field and greenhouse study has been made of the effect of nitrogen on the utilization of fertilizer phosphorus by cereal grains. A marked increase in utilization when nitrogen was mixed with either NH4H2PO4 or Ca(H2PO4)2 was shown to occur only when the nitrogen was in the ammonium form. Nitrate sources of nitrogen were relatively ineffective. Placement of nitrogen was important as increased uptake only occurred when the ammonium ion was intimately associated with the phosphorus fertilizer. This stimulative effect of the ammonium ion on phosphorus uptake occurred at a very early stage of crop growth. Rapid ammonium-ion absorption by young cereal seedlings occurred irrespective of whether the ammonium source of nitrogen was mixed with, or separated from, the phosphorus carrier. Thus the ammonium ion appears to be the dominant factor; it indirectly influences the plant's ability to take up phosphorus, rather than altering in any way the availability of the applied phosphorus fertilizer.

An examination of the method of aggregate analysis by wet sieving in relation to the influence of diverse leys on arable soils

Abstract: Summary Wet 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 centimetres.

STUDIES ON THE BASALTIC SOILS OF NORTHERN IRELAND V. CATION-EXCHANGE CAPACITIES AND MINERALOGY OF THE SILT SEPARATES (2–20μ)

Abstract: Summary X-ray and chemical studies of silt separates (2–20μ) from basaltic soils were made to determine the origin of the rather high cation-exchange capacities (C.E.C.) found for these separates. The silts as isolated by the usual method of mechanical analysis consisted in the main of quartz and feldspars with variable amounts of clay minerals which occurred as aggregates. These aggregates were of two types: (a) Composed of clay-size particles, i.e. <2μ cemented or bound into silt-size aggregates by ‘free’ sesquioxides of which the basaltic soils have a high content. The aggregates were disrupted by reduction and the clay particles subsequently released. (b) ‘Pseudo-aggregates’ which were shown to be individual particles of silt-size dimensions and having a flaky appearance. These particles were either vermiculitic (under good drainage conditions) or montmorillonitic (under poor drainage conditions), and it is suggested that they form intermediate products in the weathering of primary-rock minerals to clay minerals. Whilst the major contributor to the C.E.C. of the silts was undoubtedly the ‘pseudo-aggregates’ and to a lesser extent the true clay aggregates, most of the silt separates had a much higher C.E.C. than implied by their mineralogical composition.

A sequence of beechwood soils on the chiltern hills, england

Abstract: Summary The 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 lessive) 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, are formed.

Some chemical characteristics of ‘termite soils’ in kenya coffee fields

Abstract: Summary Chemical data are presented for a number of related topsoil, subsoil, and termite-soil samples collected in mulched coffee established on a laterized red loam coffee soil. The comparisons of mean values for soil organic carbon, total base-exchange capacity, total exchangeable bases, exchangeable calcium, and exchangeable magnesium show that there is no statistically significant mean difference between the topsoil and termite-soil sample results. The subsoil sample results, however, are significantly lower than either the topsoil or termite-soil samples in all these results. Similar comparisons of the mean values for soil pH and exchangeable calcium plus magnesium, when expressed as a percentage of the total exchangeable bases, show that the soil has been altered by Odontotermes badius(Hav.) in constructing the ‘runs; it is left with a higher pH value and with an increased proportion of the total exchangeable bases present as calcium plus magnesium. It is not possible from these results to say conclusively whether the termite soil samples are derived from the adjacent topsoil or subsoil. It is concluded that the presence of the termite soil which eventually becomes intimately mixed with the topsoil during cultivation and weed-control operations is not a point to be considered against Odontotermes badius(Hav.) when assessing the ‘pros and cons’ of its presence in mulched coffee.

Changes in the soil of a long‐continzied field experiment at saxmundham, suffolk

Abstract: Summary A four-course rotation experiment was carried out on wheat, mangolds, barley, and legumes. Yields of all crops were much increased by phosphate fertilizers, nitrogen fertilizers increased yields of non-legumes, extra yields from potash fertilizers were smaller. Fifty-six years of continuous manuring caused the following changes in the calcareous boulder clay soil: Plots receiving farmyard manure contained half as much again organic carbon as plots receiving fertilizers, plots receiving N and P fertilizers contained slightly more organic matter than plots without these fertilizers. Total soil nitrogen was considerably increased by farmyard manure and was slightly higher on plots receiving sodium nitrate than on plots without nitrogen fertilizer. Total soil phosphorus was built up by farmyard manure and by bone meal, and to a smaller extent by light annual dressings of superphosphate. ‘Soluble phosphorus’ determined by three methods differentiated clearly between plots which had received phosphate fertilirs and those which had received none. An accumulation of bone meal residues was demonstrated by dilute hydrochloric-acid extraction, but not by methods involving extraction with 0.5 M sodium bicarbonate or equilibrium with 0.01 M calcium chloride. Soluble-phosphorus values by all three methods indicated the presence of fertilizer residues more clearly than did values for total soil phosphorus. The soil contained a large quantity of total potassium and the values were not materially affected by manuring. Dilute-HCl-soluble-K and exchangeable-K values differentiated between plots which had received potash fertilizers and those which had received none. They also reflected changes in soluble potassium caused by the different amounts of potassium removed in the crops grown.

Water uptake by pure clays and soil crumbs

Abstract: Summary Wetting experiments on pure clays are described that lead to the conclusions that entrapped air is neither a necessary nor an important factor in slaking of dry soils, and that slaking is always associated with rapid intercrystalline swelling of the clay. If swelling is suppressed, or takes place slowly—as from a vapour phase— slaking does not occur, and it is suggested that slow swelling gives time for readjustment of the internal geometry of the clay, so producing some dislocation but no disruption. In N NaCl, a Na-montmorillonite swells to about twice its dry thickness, and in an atmosphere of 98 per cent. relative humidity it gains about one-third of its weight. Both these figures are in agreement with the usual estimate of surface area of 800 m.2/g. Under the same conditions a Na-illite (from Willalooka) swells by about a third of its dry thickness, and gains about a quarter of its dry weight. Studies on rates of uptake of water vapour indicate that montmorillonite has taken up less than a quarter of its equilibrium water content at 98 per cent. relative humidity within 10 min., whereas illite has taken up one-third of its water in the same time, the clays then being stable against subsequent flooding. In the field it is probable that water vapour diffuses ahead of a liquid wetting front, and the protective effect of the resultant slower pre-swelling of the clay prevents the slaking action of rain from affecting more than a thin surface layer of soil.

Problems of soil history. podzol development at goodland and torr townlands, co. antrim, northern ireland

Abstract: Summary The 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 evidence.

The soils of kerman, south persia

Abstract: Summary No mature soils were observed in the area round Kerman, much of which was occupied by lithosols and regosols. The profiles of immature soils on the fine outwash alluvium occupying some of the broad valleys suggested that the zonal Great Soil Group would be a Reddish Desert Soil. Phosphate and potassium levels of cultivated soils on the fine alluvium are adequate or good; the total nitrogen content is low, though higher on cultivated than on uncultivated soils.

STUDIES ON THE BASALTIC SOILS OF NORTHERN IRELAND IV. MINERALOGICAL STUDY OF THE CLAY SEPARATES (<2μ)

Abstract: Summary The clay separates (<2μ) isolated from the horizons of ten basaltic soil profiles are shown by X-ray analysis to have a mixedmineralogical composition; the type and amount of each mineral present being dependent on the drainage conditions within the profile. Kaolin, the end product of weathering, generally predominates in surface horizons. Vermiculite is formed in well-drained profiles, but where gleying symptoms are evident vermiculite is replaced by montmorillonite, the amount of which increases with increased degree of waterlogging. Illite occurs in only two profiles to any appreciable extent. It is inferred that soil separates other than clay are contributing to the cationexchange capacity of these soils.

Clay mineralogy of some australian red‐brown earths

Abstract: Summary The 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: Al203 ratio) 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 in the clay fraction.

Observations on the pedology and fertility of some krasnozems in northern new south wales

Abstract: Summary Eight krasnozem (red-earth) profiles representing a wide range of environments have been studied. Contrasting features of the soils can be explained by differences in parent material, climate, vegetation, and land use. The main effects corresponding to these variations are seen in the relative contents of total and readily soluble aluminium, organic carbon, nitrogen, organic phosphorus, and of exchangeable metal cations. Land utilization appears to have led to losses in organic carbon, nitrogen, organic phosphorus, exchangeable cations, and ‘available’ manganese. These losses suggest the possibility of a potassium deficiency and are in agreement with observed nitrogen deficiencies. The cation-exchange capacity of the organic matter is much greater than that of the inorganic matter, and in some soils extrapolation suggests that losses of organic matter threaten the capacity of the soils to retain cations.