bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and evaluation of general or transfer models of relationships between wheat yields and fertilizer rates in southern Australia
Authors: Colwell JD , Morton R
Published: April 2005

General or transfer models have been developed relating soil, weather and management variables to wheat yields and responses to nitrogen and phosphorus fertilizers, for a wide area of southern Australia, covering a diversity of soils and growing conditions. The models are based on sets of regressions relating polynomial fertilizer-yield functions to site variables, including dummy variables for effects of location in geographic region and kind of soil. The contributions of the dummy variables to the regressions provide measures of lack of transferability. The empirical procedures employed to evolve regression equations for the general models may produce serious statistical biases leading to exaggerated impressions of statistical significance and the reliability of predicted yields. Evidence of omission bias is provided by the need for dummy variables, the substantial residues in analyses of variance, and doubts concerning causal effects by some of the predictor variables. Selection bias is expected from the use of the same set of data both to select variables and to estimate parameters, and by the lack of a theoretical basis to define the form of the regression models. Until improvements in these respects have been provided by basic research, some protection from the effects of these biases may be sought in large samples. General models offer advantages in this respect over soil or locality specific models.
Temporal fluctuations in biochemical properties of soil under pasture. II. Nitrogen mineralization and enzyme activities
Authors: Ross DJ , Speir TW , Cowling JC , Whale KN
Published: April 2005

Temporal fluctuations in rates of nitrogen mineralization and the activities of six enzymes were measured in topsoil, predominantly a Typic Haplaquoll, from two plots that contained pastures of different age in the Wairarapa area. Samples were taken at c. 4-weekly intervals for over one year. Organic carbon contents averaged 6.7 and 3.6% in soil from the older and younger pastures respectively. Net mineral-nitrogen production at 25�C was higher in soil at a standardized water potential (-3 and -4 kPa for soil from the older and younger pastures respectively) than at field moisture content. It was initially higher in soil from the younger than from the older pasture. Generally, distinct seasonal patterns were not apparent. All of the enzyme activities showed significant temporal fluctuations. Amylase and cellulase activities fluctuated more than invertase activity, but all three carbohydrase activities were generally high in wet spring samples. When plot effects were removed, only the fluctuations in amylase activity were related positively and significantly to soil moisture content. Fluctuations in cellulase, urease, phosphatase and sulphatase activities were correlated negatively with soil moisture content. The temporal fluctuations in enzyme activities were, when plot effects were removed, mainly independent of the small variations that occurred in soil organic carbon and total nitrogen contents. Interrelationships of these biochemical properties, and relationships with rates of CO2 production and indices of microbial biomass, are discussed.
Decomposition of plant material in Australian soils. II. Residual organic 14C and 15N from legume plant parts decomposing under field and laboratory conditions
Authors: Amato M , Jackson RB , Butler JHA , Ladd JN
Published: April 2005

14C- and 12N-labelled Medicago littoralis and Medicago truncatula plant parts, ground or unground, were added at a rate equivalent to 50 kg nitrogen ha-l to a calcareous soil in the field and allowed to decompose for two years. Both plant types behaved similarly but the various plant parts decomposed to different extents. After 4 weeks' and 2 years' decomposition respectively, the residual organic 14C in soil from leaves of both Medicago species accounted for about 62% and 20% of input, from stems 70% and 24% and from roots 80% and 32%. Average residual organic 15N accounted for 64% and 40% of leaf 15N, 87% and 56% of stem and 81% and 50% of root 15N. Grinding had no effect on the residual 14C and 15N of plant parts. After 2 years' decomposition the proportion of residual and 15N present as labelled biomass was greatest for leaf residues. Results from laboratory studies of 20 weeks' decomposition of ground and unground Medicago littoralis plant parts under continuously moist and intermittently dry and rewetting conditions were consistent with field results. Grinding significantly promoted pod decomposition under most incubation conditions. Drying and rewetting promoted decomposition of the plant parts. Pods were affected more than other parts. The longer the time moist following drying, the greater the decomposition. The more frequent the drying and wetting cycles, the greater the decomposition.
Occurrence and source of quartz in six basaltic soils from Northland, New Zealand
Authors: Stewart RB , Neall VE , Syers JK
Published: April 2005

Quartz abundance, distribution and oxygen isotope composition was determined for six basaltic soils from Northland, New Zealand. Quartz > 125 �m in size occurred in two soils, the Kiripaka and Ruatangata. �18O values of 8.2% for the >250 �m sized quartz in both soils and 8.1-8.4� for that in the 250-125 �m size fraction of the Ruatangata indicate a high temperature origin for this quartz. A probable origin is from air-fall rhyolitic tephra (particularly Kaharoa Ash) erupted from the central North Island. Another potential source is quartzose beach sand from the western (windward) coast of Northland. Quartz from these beach sands has a �18O value of 8.7�, also indicating a high temperature origin. Quartz in the 63-20 �m size fractions of the basaltic soils has a mean 6180 value of 12.0�, consistent with derivation from local sedimentary rocks as loess. Quartz in the 5-2 �m fraction of the soils has a mean �18O value of 13.9�, similar to that of aerosolic dusts previously reported from this latitude. The Kiripaka soil had anomalously high �18O values of 17.3-19.6� for 5-2 �m sized quartz. This quartz can be shown to originate from marine shales in the vicinity of the soil profile sampled and indicates that local sources may contribute to the 'aerosolic' size fraction of soils in addition to tropospheric aerosolic dust.
Identification of dispersive behaviour and the management of red-brown earths
Authors: Rengasamy P , Greene RSB , Ford GW , Mehanni AH
Published: April 2005

A scheme is proposed, together with a procedure suitable for routine laboratory use, for the prediction of dispersive behaviour of surface layers of red-brown earths and their classification into one of six classes. Each class is defined on the basis of predictive relationships established between dispersion (spontaneous and mechanical), sodium adsorption ratio (SAR) and total cation concentration (TCC). These relationships were established experimentally using 138 samples representing both surface and subsurface layers from 69 red-brown earth profiles. Preliminary studies including samples from red clay and black earth profiles indicated that the proposed scheme is not suitable for these soils. Neither can it be used for soils containing free lime. The procedure proposed enables the prediction of the probable dispersive behaviour of the surface layer of red-brown earths, including exposed subsoils. It provides a rational basis for the formulation of appropriate management strategies for the manipulation of the surface structure of individual red-brown earths used for dryland or irrigated agriculture. Application of the proposed scheme to the estimation of the minimum level of residual gypsum required to maintain aggregate stability via the electrolyte effect is discussed, with special reference to low-sodic soils (i.e. with a SAR below 3, e.g. Classes 2a and 3c).
Effects of waterlogging and subsequent drainage of a pasture soil on phosphate sorption, extractable phosphate and oxalate-extractable iron
Authors: Bradley J , Vimpany I , Nicholls PJ
Published: April 2005

Undisturbed cores of a pasture soil from the central tablelands of New South Wales were waterlogged for periods varying from 4 to 42 days and then drained to simulate seasonal waterlogging. Phosphate sorption, Bray 1 extractable phosphate and oxalate-extractable iron levels were measured before watering, at the end of waterlogging and up to 90 days after draining. Increasing the duration of waterlogging increased the logarithms of phosphate sorption and Bray 1 extractable phosphate linearly, but the response equation of log oxalate iron was significantly quadratic. When drained, all three levels fell, but the positive sorption response to waterlogging remained 90 days after draining. These results are consistent with those from previous studies that found phosphate solubility to be associated with the reduction of iron during waterlogging and its subsequent oxidation on drying. The agronomic implication of the findings for superphosphate topdressing of seasonally waterlogged soils is discussed.
Medium and short range variability in textural layering in an ochrept developed on an alluvial floodplain
Authors: Karageorgis D , Tonkin PJ , Adams JA
Published: April 2005

The nature and extent of textural layering was investigated in 367 profiles described during a 30 by 30 m grid survey of an area of Ochrepts developed on a Holocene floodplain in the South Island of New Zealand. The typical profile texture form (to 1 m) consists of a uniform textured layer of varying thickness (but less than 60 cm), underlain by a texturally layered portion in the B horizon and below. Textures in the layered portion ranged from heavy silt loams to sands. The number of layers ranged from one to thirteen with six to eight being the most usual. The pattern of textural layering is random and hence unpredictable, and is the result of sedimentary depositional processes forming the parent material of these alluvial soils. Continuous (short range) lateral variability in textural layering was similar to that identified during the 30 by 30 m grid survey.
The effect of chemical extractant on the estimation of rock phosphate fertilizer dissolution
Authors: Hughes JC , Gilkes RJ
Published: April 2005

Rock phosphates have been widely used in the acid soils of the tropics as direct application fertilizers. To estimate their rate and extent of dissolution various chemical extractants have been used. However, the acidic or inadequately buffered nature of these extractants promote extensive dissolution of the apatite and may result in a gross overestimate of the amount of rock phosphate dissolved. To overcome this problem, it is proposed that the soil is shaken for 1 h in 2 M barium chloride buffered at pH 8.1 with triethanolamine (solid : solution ratio of 1:10) and calcium determined in the filtered supernatant. The difference in extractable calcium between fertilized and unfertilized soil is a measure of the dissolution of the rock phosphate.
Longitudinal profile of trends in salinity in the river Murray
Authors: Morton R , Cunningham RB
Published: April 2005

Statistical analyses have been performed on series of electrical conductivity (EC) measurements taken over the past 16 years from 8 stations on the River Murray to assess changes in salinity along the river and trends over time. Below Euston, N.S.W., salinity has generally increased over time, although the log-linear trends were statistically significant at only three stations: Red Cliffs, Morgan and Mannum. The increase in EC of over 1% p.a. at Red Cliffs was partly removed when it passed to Merbein, and we attribute this to the Lake Hawthorn salinity interception scheme. Both Morgan and Mannum showed increases of over 2% p.a., confirming the results of our earlier analysis of chloride data from Morgan, and current levels there are close to the desirable limit of 800 �S/cm. Thus major adverse effects can be anticipated if the rate of increase over the last 16 years is allowed to continue.
Measuring air-filled porosity changes in an irrigated swelling clay soil
Authors: Jayawardane NS , Meyer WS
Published: April 2005

An in-situ method for measuring air filled porosity (�a) of soils using a neutron meter was developed and evaluated for a layered, swelling clay soil. Bulk density-volumetric moisture content relationships of soil layers were used to calculate the regressions of volumetric moisture content on �a. These regressions were combined with calibration equations of the neutron meter to obtain relationships between �a and neutron counts. The �a values predicted from measured neutron count ratios show good agreement with �a values calculated from the measured bulk densities and moisture contents in a transitional red-brown earth. The method provides a rapid and non-destructive measurement of �a. Soil aeration in a transitional red-brown earth under two irrigation treatments was assessed using neutron counts to monitor the changes in �a profiles. Large soil cores which were flooded had lower profile �a values than did cores which were not flooded. However, differences were small, owing apparently to the very low rates of infiltration and redistribution. The potential use of this method to continuously monitor changes in �a profiles allows frequent calculation of aeration stress indices, which may be used to predict crop responses and yield losses due to poor aeration.
Distribution, salinity, kinetic and thermodynamic characteristics of urease activity in a vertisol profile
Authors: Dalal RC
Published: April 2005

The distribution, and the effects of temperature, moisture and organic C substrate on urease activity of a vertisol up to 120 cm depths were studied. The kinetic and thermodynamic characteristics of urease activity in the soil were also studied. Urease activity (measured at the natural soil pH) was found to be higher in soil at 20-60 cm than in the top soil (0-10 cm). It remained relatively constant for up to 900 days, when the soil was kept either field moist at 4�C or air-dried at 25�C. However, partial drying of the soil or rewetting of air-dried soil, especially at elevated temperatures (40�C), and glucose addition, affected substantially but differentially the urease activity of soil obtained from different depths. The distribution in soil urease activity assayed at an optimum pH (using tris-HCl buffer, pH 9.0) became relatively uniform at all depths. From the effect of different buffer pH's on soil urease and from kinetic and thermodynamic characteristics, it is suggested that lower urease activity in the top soil was primarily a consequence of suboptimal pH, resulting in greater configurational or steric hindrance in formation and/or breakdown of urea-urease complex in the soil. Differences in seasonal variation in temperature, moisture, organic substrate and microbial activity may also affect distribution and stability of urease at different depths.
An assessment of pedoturbation by two species of mound-building ants, Camponotus intrepidus (Kirby) and Iridomyrmex purpureus (F. Smith)
Authors: Cowan JA , Humphreys GS , Mitchell PB , Murphy CL
Published: April 2005

Details of the size, structure and occurrence of Carnponotus intrepidus nests and the size, composition and source of the mound cover on Iridomyrmex purpureus nests are reported from several areas of eastern New South Wales. Both species are common, and construct large mounds of mixed topsoil and subsoil with surface covers, which appear to protect the mound from rainsplash erosion. Camponotus thatches the mound with charcoal, leaves and twigs; Iridomyrmex covers the mound in granules of inorganic or organic material that are sufficiently large to absorb most raindrop impact energy. This material is collected from the surface and carried 10-15 m to the nest. Rainsplash erosion protection is probably a factor contributing to nest longevity, which may be as much as 100 years for Iridomyrmex. It is concluded that, despite the impressive size of the nests and the selective use of materials, neither species is very significant in terms of soil mixing when compared with the smaller, more common ant Aphaenogaster longiceps.
Influence of different organic wastes upon water retention, transmission and contact characteristics of a sandy soil
Authors: Kumar S , Malik RS , Dahiya IS
Published: April 2005

Small cylinders were filled to a depth of 20 cm with Ludas sand to which different organic wastes, viz. sewage sludge, press mud, green manure and farmyard manure had been added up to a maximal rate equivalent to 827, 1043, 1370 and 542 t/ha. The cylinders were set in the ground and kept moist. At the end of 308 days' equilibration period, the samples were used for measuring soil water retention, saturated hydraulic conductivity as well as the horizontal infiltration with 0.01 M CaCl2 and alcohol. An apparent advancing contact angle was calculated from the last two measurements. The incorporation of all the organic wastes caused an appreciable increase in the amount of water retained at a given pressure potential. Increase in available water was caused by the application of sewage sludge and press mud only. Hydraulic conductivity, penetration coefficient and cumulative horizontal infiltration decreased markedly with additions of these materials. The maximum decrease in hydraulic conductivity was in case of press mud (93%), whereas the maximum decrease in penetration coefficient was in case of farmyard manure (81%). The contact angle, which plays an important role in penetration of water into porous materials, increased more in conventional organic manures (green manure and farmyard manure) than in municipal and industrial wastes (sewage sludge and press mud).
Corrigenda - The chemical composition and ionic strength of soil solutions from New Zealand topsoils
Authors: Edmeades DC , Wheeler DM , Clinton OE
Published: April 2005

In preliminary experiments a centrifuge method for extracting soil solutions was examined. Neither the time nor speed of centrifuging had any effect on the concentrations of cations in soil solution. The concentration of cations increased with decreasing soil moisture content, and NO3, Ca, Mg, and Na concentrations increased with increasing time of storage of freshly collected moist soils. It was concluded that to obtain soil solutions, which accurately reflect the soil solution composition and ionic strength (I) in situ, requires that soil samples are extracted immediately (<24 h) following sampling from the field. Prior equilibration of soil samples, to adjust soil moisture contents, is therefore not valid. The effect of time of sampling and soil type, and the effects of fertilizer and lime applications, on soil solution composition and ionic strength, were measured on freshly collected field moist topsoils. Concentrations of Ca, Mg, K, Na, NH, and NO, were lowest in the winter and highest in the summer. Consequently, there was a marked seasonal variation in ionic strength which ranged from 0.003 to 0.016 mol L-1 (mean, 0.005 s.d. 0.003) over time and soil type. Withholding fertilizer (P, K, S, Ca) for two years had only a minor effect on ionic composition and strength, and liming increased solution Ca, Mg and HCO3, but decreased Al, resulting in a twofold increase in ionic strength. These results suggest that the ionic strength of temperate grassland topsoils in New Zealand lie within the range 0.003-0.016 and are typically 0.005.
Active and exchangeable cations in soils
Authors: Tucker BM
Published: April 2005

The amounts of cations, Ca, Mg, K and Na, that could be extracted from soils by salt solutions varied with the cations, anions, acidity or alkalinity, and solvent of the extracting reagent. The variations were largest for soils that contained organic matter as the main source of those cations, and smallest in clay soils with little organic content. Calcium was the cation most affected and sodium the least affected. It appeared that the extractants removed all diffuse double-layer exchangeable cations, and variable portions of the other active cations including inner-sphere cations, specifically adsorbed cations, and those chelated by organic materials. A moderate, non-specific extractant containing a quaternary ammonium salt, choline chloride, is recommended for the displacement of exchangeable cations with a minimum contribution from other active cations. For an estimate of all forms of active cations, e.g. for soil nutrient assessment, a solution of ammonium sulfate is suggested.
The effect of soil pH on the formation of VA mycorrhizas by two species of Glomus
Authors: Abbott LK , Robson AD
Published: April 2005

Two species of vesicular-arbuscular (VA) mycorrhizal fungi differed in their ability to infect subterranean clover roots when soil pH was changed by liming. In a glasshouse experiment, Glomus fasciculatum infected extensively at each of four levels of soil pH (range 5.3-7.5). Glomus sp. (WUM 16) only infected extensively at the highest pH level. Liming the soil depressed plant growth, but this effect was almost entirely overcome by inoculation with G. fasciculatum. In the second experiment, Glomus sp. (WUM 16) failed to spread from existing infection within roots of subterranean clover when soil pH was 5.3 or lower. The lack of spread of infection was associated with an inability of hyphae of this fungus to grow in the soil used unless it was limed to give a pH at least greater than 5.3.
Earthworm activity in irrigated red-brown earths used for annual crops in Victoria
Authors: Tisdall JM
Published: April 2005

Few earthworms were found in January (15 m-2) or September (21 m-2) 1983 in surveys of irrigated soils used commercially for pastures in the Goulburn Valley, Vic.; only the introduced lumbricids were found. No earthworms were found in January 1983 in a survey of irrigated annual crops on similar soils; the soils had each supported irrigated pasture the previous year. However, in carefully managed experimental soils, i.e. with at least 10 t ha-' of cow manure added per crop with mild or no cultivation, used for double-cropping or lucerne, relatively high numbers (up to 86 m-2) of earthworms were present; these included lumbricids, the genera which are usually the most useful in terms of soil structure, and the native megascolecids. No mature lumbricids were found in January in plots without cow manure. Ample food is needed to enable relatively high numbers of lumbricids to develop in row-crops in the Goulburn Valley, and for very high numbers, the surface soil should be kept moist throughout summer. Macroporosity (20-80 mm depth), infiltration and number of biopores (50 mm depth) were each higher in the non-cultivated systems with cow manure than in the cultivated control (no cow manure added). Numbers of biopores in January 1984 were directly related to total numbers of earthworms in January 1984.
Shallow groundwaters in weathered volcanic, granitic and sedimentary rocks in relation to dryland salinity in southern New South Wales
Authors: Gunn RH
Published: April 2005

Soils affected by secondary salinization were studied in six areas on the Southern Tablelands of New South Wales. All the salt-affected areas are underlain by, or occur in close proximity to, deeply weathered volcanic, granitic and sedimentary rocks which commonly contain stores of soluble salts, dominantly sodium chloride. The chemical composition of shallow groundwaters in the areas was monitored by piezometers for periods of up to two years. Water levels in the piezometers responded rapidly to rainfall, but the ionic composition of the waters generally remained fairly uniform. All waters are dominated by sodium chloride; those with the highest contents occurred in volcanic and granitic rocks, followed by Ordovician sediments and the lowest contents were in Silurian sediments. The chlorine contents in samples of weathered rocks follow a similar sequence. Electron microprobe analyses indicate that the chlorine-bearing minerals in the unaltered rocks are principally biotite, hornblende and potassium, sodium and calcium feldspars. No salt-affected soils were found in areas underlain by unweathered rocks.
Hydrograph recession characteristics of some small agricultural catchments
Authors: Boughton WC , Freebairn DM
Published: April 2005

Five-min recession constants were calculated for surface runoff and interflow using hydrographs of runoff from five 1-ha catchments at Greenmount near Toowoomba in south-east Queensland. The recession constants were converted to half-flow periods, i.e. the time required for flow rate to halve during an exponential recession. The half-flow periods of surface runoff and interflow on the 1 ha catchment are compared with published data from catchments of much larger size in New South Wales, and it is shown that the ratio of interflow half-flow period to surface runoff half-flow period does not vary much over six orders of magnitude of catchment size. Calculations of maximum rates of interflow and volumes of interflow storage show that both rates and volumes are possible in the plough depth of surface soil. The results support the evidence of interflow obtained earlier in unit hydrograph studies of runoff on these same catchments.
A portable, microcomputer-controlled drip infilrometer. I. Design and operation
Authors: Ross PJ , Bridge BJ
Published: April 2005

This paper describes a lightweight, portable drip infiltrometer that uses a dripper unit swung from a collapsible aluminium frame. The dripper unit, constructed of plastic tubing and hollow polythene needles, gives a uniform application rate over 1 m2, and no water is wasted outside that area. A microcomputer controls the rate, which can be varied between 1 mm h-1 and 150 mm h-1, and allows a series of rates and times to be preprogrammed to simulate differing types of rainfall. The infiltrometer can be assembled and operating within 15 min and moved to an adjacent plot in 5 min. Laboratory tests showed that the coefficient of variation over the 1 m2 was 2-4% for a wide range of application rates. A field test demonstrated the usefulness of the infiltrometer in following the ponded infiltration rate with time. Calculated sorptivities were lower than those obtained from ponded ring infiltrometer measurements.
A portable microcomputer-controlled drip infiltrometer. II. Field measurement of sorptivity, hydraulic conductivity and time to ponding
Authors: Bridge BJ , Ross PJ
Published: April 2005

The lightweight portable drip infiltrometer described in Part I was used to determine the infiltration characteristics of a sandy loam soil. Sorptivity was determined by varying the application rate to maintain surface ponding and by measuring the time to ponding at a constant application rate. Saturated hydraulic conductivity was equated to the long-time steady-state application rate needed to maintain surface ponding. This rate could be determined to a precision of 0.5 �m s-1 (2 mm h-1) and agreed well with core data from 0.5 to 1.0 m depth in the profile. The results obtained were compared with ponded ring infiltrometer measurements. Sorptivities calculated from the ring infiltrometers were greater than those from the variable rate drip infiltrometer which in turn were greater than those from the constant rate drip infiltrometer. This was attributed to the effect of the macropores under the ponded rings and to confining the depth over which sorptivity was measured under constant application rate to the wetter surface soil. In dry soil, the drip infiltrometer measured low initial infiltration rates caused by poor wetting of the soil, but these were not measured by the ponded ring infiltrometers, which had a 50 mm head. In moist soil, poor wettability did not occur. Five equations for calculating sorptivity from measurements of time to ponding under a constant application rate of 8.3 �m s-1 (30 mm h-1) were used and four of these equations agreed within 20%. This was less than the range of sorptivities arising from uncertainties in determining the time to ponding, and the differences between the equations were attributed to the assumptions used in their derivation. It was concluded that any measurement of sorptivity on this soil was difficult to interpret because of non-uniformity in the upper soil profile.
The partitioning of exchangeable magnesium, calcium and sodium in relation to their effects on the dispersion of Australian clay subsoils
Authors: Tucker BM
Published: April 2005

Clay subsoils were analysed by a procedure that uses a choline chloride reagent to distinguish double-layer exchangeable cations from other more strongly adsorbed forms extractable by an ammonium sulfate reagent. In those clay subsoils that contained little organic matter, the exchangeable cations made up nearly all of the cations that reacted with salt solutions. This means that it makes no practical difference to values of Ca/Mg ratios, or of ESP, whether the analytical methods discriminate between those exchangeable cations and other adsorbed cations, or do not, provided the soil samples contain little organic matter. The adoption of the new choline chloride method will not make necessary any revision of the criteria already in use in Australia for sodium- or magnesium-affected subsoils. Some possible mechanisms for the deleterious effect that large amounts of exchangeable magnesium have on the properties of subsoil clays containing illite are discussed. It is shown that the single-charged cations MgCl+ or MgOH+ are not involved. The clays hold exchangeable magnesium slightly less strongly than they hold calcium, and this weaker binding remains the best explanation for the magnesium effect.
Effects of phosphate buffer capacity on yield response curvature and fertilizer requirements of wheat in relation to soil phosphate tests
Authors: Holford ICR , Cullis BR
Published: April 2005

Data from 39 fertilizer field experiments in north-western New South Wales were used to examine the effects of phosphate buffer capacity on yield response curvature and fertilizer requirements of wheat in relation to six soil phosphate tests (Bray1, Bray2, BSES, Truog, lactate, and bicarbonate). The soil tests were also evaluated for their accuracy in predicting yield responsiveness in a total of 48 experiments. There was a highly significant negative correlation between buffer capacity and response curvature, accounting for nearly 50% of the variance in curvature. The accuracy of the relationship was highest for moderately and strongly buffered soils. When used to predict curvature and hence fertilizer requirements, buffer capacity increased the variance accounted for by the most effective soil test (lactate) from 32% to 75%, compared with 93% using actual response curvatures. Whether used to predict responsiveness or fertilizer requirement, the lactate test was superior and the bicarbonate test was inferior to other soil tests. The bicarbonate test accounted for only half as much variance in responsiveness as the lactate test, and it accounted for none of the variance in fertilizer requirement. The results confirmed earlier studies showing that the bicarbonate test has several intrinsic properties which make it inferior to other soil tests on moderately acid to alkaline soils.
Soil temperature and the energy balance of vegetative mulch in the semi-arid tropics. II. Dynamic analysis of the total energy balance
Authors: Ross PJ , Williams J , Mccown RL
Published: April 2005

Soil temperatures and water losses under killed vegetative mulch canopies are examined in the context of no-tillage crop production, using a numerical dynamic model of the soil, canopy and lower atmosphere. Both liquid and vapour movement in the soil are included, as are free and forced convection in the canopy. The predictions of the model for a clay loam soil are as follows. Medium and heavy mulches reduce the water loss over six days by 1.4 and 2.7 mm respectively, the reduction occurring while the soil surface is wet. This small effect is important in giving seedlings an extra 2 or 3 days for establishment. Water loss from bare soil and under a medium mulch is limited by soil resistance even on the first day of evaporation from initially wet soil. Mulch canopies that intercept 80 and 50% of incoming radiation can keep surface soil temperatures within 10 and 20�C respectively of ambient, whereas bare soil temperatures may rise 30�C above ambient. A moderate wind reduces soil temperatures under a mulch only a few degrees, but cools the canopy much more. A rough soil surface helps cool the soil. Water losses and soil temperatures are little affected by a 50% change in soil water diffusivity or thermal conductivity. An extensive mulched area results in temperatures well above those observed on small plots surrounded by transpiring vegetation, which maintains cool air above the mulch. A simplified form of the model, which incorporates only a single mulch layer and which ignores effects of wind, yields soil temperatures which are not greatly different from those generated by the more complex model for wind speeds below 1 ms-1 at canopy height.
Occurrence and properties of lepidocrocite in some soils of New Zealand, South Africa and Australia
Authors: Fitzpatrick RW , Taylor RM , Schwertmann U , Childs CW
Published: April 2005

Fifty-one samples, collected from 26 sites in New Zealand, South Africa and Australia, were tested for the presence of lepidocrocite (�-FeOOH) and goethite (�-FeOOH). The samples were predominantly orange-coloured mottles, bands, crusts and pipestems from hydromorphic soils, but also included a placic horizon, iron-rich precipitates from water courses, altered pyrite cubes, and geode-like features in weathered saprolites. The iron oxides were identified and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Lepidocrocite was identified in 49 of the samples, and in 44 was present in concentrations exceeding I%, with the highest being approximately 70%. Crystallinities of the lepidocrocite were assessed from the widths and positions of XRD peaks, and, in some cases, from TEM. Goethite was also present in most samples, and predominated over lepidocrocite in some. In all three countries, the most common occurrence of lepidocrocite was associated with the gleyed soil materials commonly found in wet, poorly drained pseudogley soils (mostly 'humic slope gley') of humid temperate climate. Under these climatic conditions the high degree of water supply, relatively lower soil temperatures, lower evaporation and slower water movement caused reductomorphic conditions. At these sites soil iron oxides are reduced and, on reoxidation, lepidocrocite and goethite are generally formed. The colour generally associated with lepidocrocite in iron-rich segregations in hydromorphic soils is 7.5YR6-7/4-8 Lepidocrocite was also identified in all of the other samples mentioned above. A study of the relative proportions of lepidocrocite and goethite, and the crystallinity of these associated minerals in the various morphological concentrations (profile trends), suggests that their formation is strongly governed by soil microenvironmental factors (pH, Eh, and ionic environment). However, climatic and pedogenic factors such as podzolization and high organic matter contents may modify these mineral phases or induce further transformation. These findings indicate that lepidocrocite occurs in a remarkably wide range of materials and weathering environments. Moreover, the morphology, crystallinity, differential XRD line broadening and line shift of the lepidocrocite, and the commonly associated goethite also vary markedly in the respective materials. This suggests that other factors associated with particular weathering environments, such as those involved in pseudomorphous alteration of pyrite and the influence of chloride ions, may be more important in the formation of lepidocrocite than the conditons associated with hydromorphy. The morphology and characteristics of lepidocrocite and goethite, together with field associations, appear to be useful indicators of soil genesis.
Origin and assessment of water repellency of a sandy South Australian soil
Authors: Ma'shum M , Farmer VC
Published: April 2005

The water repellency of a sandy lucerne pasture soil is critically dependent on aqueous extraction and subsequent drying procedures. Freeze-drying converts a very severely water-repellent soil into a readily wettable soil, but subsequent rewetting and oven-drying regenerates water repellency. These changes are ascribed to changes in the molecular conformation of the organic matter. Prolonged shaking detaches organic matter coatings from sand particles and so reduces repellency. Allowing for these effects, it is shown that a sequence of alcohol-benzene extraction, acid leaching, and NaOH extraction removes the major part of the water-repellent substances present.
Urease and dehydrogenase activity of alkali and reclaimed soils
Authors: Rao DLN , Ghai SK
Published: April 2005

Alkali soils have low amounts of organic carbon and nitrogen and low levels of urease and dehyrogenase activity. There is a marked improvement in these properties after reclamation by chemical or biological methods. After 12 years, greatest accumulation of organic matter and enzymes was found in soils with a tree cover, followed by those with a grass cover, and it was least in soils reclaimed by application of a chemical amendment (gypsum) followed by cropping. The enzymatic activities were correlated positively with organic carbon and Kjeldahl nitrogen and negatively with pH and CaCO2. Organic carbon accounted for most of the variation in enzymatic activities.
Neutron moisture meter : the dependence of their response on soil parameters
Authors: Wilson DJ , Ritchie AIM
Published: April 2005

A multigroup diffusion theory calculation based on a nuclear reactor neutronics code is used to determine the response of a neutron moisture meter to changes in soil parameters such as dry soil density, soil water content, thermal neutron absorption cross-section and neutron scattering crosssection. Empirical equations which fit the results can be used to estimate the response at values of the soil parameters other than those used in the calculations. These equations can also be used to estimate the accuracy with which the parameters must be known to achieve a required accuracy in the derived soil water content.
Soil temperatures during and following low-intensity prescribed burning in a Eucalyptus pauciflora forest
Authors: Raison RJ , Woods PV , Jakobsen BF , Bary GAV
Published: April 2005

Temperatures at the soil surface and at several soil depths were measured during, and at intervals, for 33 months after a low-intensity prescribed burn in a subalpine Eucalyptus pauciflora forest. The high organic matter content, low bulk density, and low moisture content of the surface soil caused steep soil temperature gradients to be generated during the fire. Mean maximum temperatures during the fire were 600 � 50, 450 � 52, 54 � 5 and 42 � 5�C in the litter and at 0, 2 and 5 cm soil depths respectively. The highest temperatures recorded at 0, 2 and 5 cm depths were 703, 94 and 44�C. Temperatures exceeding 200�C, which result in volatilization of N from soil organic matter, were estimated to have occurred in the upper 3 mm of the soil. Byram fire intensity tended to be negatively correlated with the maximum temperature measured at the soil surface, but was not correlated with the amount of heat absorbed by black cans (thermal integrators) or the increase in the heat content of the soil. After the burn, the mean daily maximum temperatures in the soil were markedly higher on burnt than on unburnt sites. For example, soon after burning increases were 6, 10, 4 and 4�C at 0, 2, 5 and 10 cm depths, respectively, during a 5-day summer period. Mean daily minimum temperatures on recently burnt plots were similar to or slightly lower than those on unburnt areas. Average day-time temperature in recently burnt forest in summer was elevated by up to 8 and 4�C at 0 and 10 cm soil depths.
Effects of fumigation on soil nitrogen, plant nitrogen and root disease incidence in wheat at Wongan Hills, Western Australia
Authors: MacNish GC
Published: April 2005

Fumigation of three Western Australian wheat field soils with a mixture of chloropicrin and methyl bromide (2:l) caused changes in soil nutrients and microflora which resulted in increased vegetative growth at all sites, leading to increased grain yields on the two light soils (33 and 49% respectively) but not on the heavy soil, probably because of dry conditions during the grain filling period. Soil fumigation increased concentrations of mineral nitrogen in soil early in the season. Ammonium nitrogen in fumigated soil 49 days after treatment ranged from 18.2 to 26.5 ppm, compared with 1.4-2.2 ppm in untreated soil, while nitrate nitrogen ranged from 0.3 to 2.1 ppm and 1.5 to 7.9 ppm respectively. Much of the growth increases appear to be due to this nitrogen and to a lesser extent the reduction of Gaeumannomyces graminis var. tritici. The possibility that minor pathogens like Fasarium avenaceum, Microdochium bolleyi and weakly pathogenic forms of Rhizoctonia spp. contributed to yield reduction is considered to be unlikely.
Characteristics of soil and productivity of Pinus radiata (D Don) in New South Wales .I. Relative importance of soil physical and chemical parameters
Authors: Turvey ND , Rudra AB , Turner J
Published: April 2005

The objectives of the study were to determine whether selected soil physical and chemical parameters could be used as predictors of site and the productivity of Pinus radiata (D. Don). The study was carried out in the Lithgow district of New South Wales. Sixty plots were located in first-rotation unthinned stands of P. radiata of age 11 years. None of the stands had received fertilizer. The stands were selected to cover a wide range of merchantable volume production (0-175 m3 ha-1), and were located on a range of geological types including siltstone, medium-grained quartz sandstone, conglomerate, and rhyolitic tuff and lava. Soil depth was positively correlated, and per cent sand negatively correlated with all stand production variables. No other soil physical-or chemical variables were correlated consistently with stand variables. Discriminant analysis was used to test for the ability of a selected subset of soil physical and chemical variables to discriminate (a) between three volume production classes, and (b) between three geological groups. Soil depth, per cent sand, and total nitrogen contributed to two functions which discriminated between volume production groups. Cation exchange capacity, Bray phosphorus, per cent sand, exchangeable sodium, and total nitrogen contributed to two functions which discriminated between geological groups. Thus soil physical parameters were predominant in discriminating between volume production groups, and soil chemical parameters were predominant in discriminating between geological groups.
Podzolized soils on hilly and steep land near Tennyson Inlet, Marlborough Sounds, New Zealand - Classification and relation to Landform, Slope and Altitude
Authors: Laffan MD , Daly BK , Whitton JS
Published: April 2005

Eight soil profiles ranging in altitude from 30 m to 820 m at Tennyson Inlet in the Marlborough Sounds, New Zealand, are described, classified and discussed in terms of morphology, chemistry and clay mineralogy. The soils are formed from greywacke on forested hilly and steep land under a superhumid climate. Profiles show eluvial and/or illuvial features typical of podzols and podzolized soils. Within the study morphological, chemical and mineralogical properties show patterns in weathering, leaching and podzolization. Differences in weathering are related mainly to geomorphic history and topography. The most strongly weathered soils occur at altitudes below about 200 m where parent materials were probably inherited from Late Pleistocene interglacial or interstadial weathering. Less weathered soils occur at higher altitudes where parent materials were derived from widespread periglacial erosion during the last glaciation, and from periodic erosion during the Holocene. Weathering and also leaching is least on soils on very steep slopes (>38�) at altitudes above 200 m, where rejuvenation by slope movement has been more active than on less steep slopes. Patterns in weathering are clearly shown by clay mineralogy, with strongly weathered soils dominated by kaolinite, and less weathered soils dominated by vermiculite. Differences in podzolization are attributed mainly to greater effective rainfall, leaching and accumulation of amorphous minerals and mineral-organic complexes with increasing altitude. The combination of field and laboratory data shows that at altitudes below about 200-300 m profiles are relatively weakly podzolized, while podzolized soils and podzols occur at higher altitudes. Podzolization patterns are clearly shown by subsoil values of acid-oxalate and pyrophosphate Fe and Al, NaF, pH and P retention. The profile at highest altitude is dominated by smectite clays and the greyish-coloured solum is interpreted mainly as a relatively thick (80 cm) eluvial horizon resting directly on bedrock. Neither the New Zealand Genetic Classification nor Soil Taxonomy satisfactorily classifies all the soils.
The effect of soil properties and level of fertilizer application on the dissolution of sechura rock phosphate in some soils from Brazil, Colombia, Australia and Nigeria
Authors: Hughes JC , Gilkes RJ
Published: April 2005

The extent and rate of dissolution of Sechura rock phosphate in 30 soils from Brazil, Colombia, Australia and Nigeria were measured. There was an initial rapid dissolution within 1 day, and this was followed by slower dissolution up to 124 days. For all soils an increase in the level of rock phosphate resulted in a smaller proportion dissolving. After 31 days, the percentage dissolved differed widely between soils and for rock phosphate application levels of 0.34 and 34 mg g-1 soil ranged over 0-100%, and 0-21% respectively. Pyrophosphate and oxalate-extractable iron and aluminium were important soil properties for predicting the amount of rock phosphate dissolution; pH, organic carbon, silt content and exchangeable calcium were subsidiary predictive properties for some soils.
Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. II. Total organic carbon and its rate of loss from the soil profile
Authors: Dalal RC , Mayer RJ
Published: April 2005

The kinetics of organic C loss were studied in six southern Queensland soils subjected to different periods (0-70 years) of cultivation and cereal cropping. The equation: Ct = Ce + (C0 - Ce)exp(- kt), where C0, Ce and C, are organic C contents initially, at equilibrium and at time k respectively, and k is the rate of loss of organic C from soil, was employed in the study. The parameter k was calculated both for %C (kc) and for weight of organic C/volume of soil (k,), determined by correcting for differences in sampling depth due to changes in bulk density upon cultivation. Mean annual rainfall largely determined both C, and Ce, presumably by influencing the amount of dry matter produced. Values of kc and kw varied greatly among the soils studied. For the 0-0.1 m depth, kw was 0.065, 0.080, 0.180, 0.259, 0.069 and 1.224 year-1 respectively for Waco (black earth - initially grassland), Langland-Logie (grey brown and red clays - brigalow), Cecilvale (grey, brown and red clays - poplar box), Billa Billa (grey, brown and red clays - belah), Thallon (grey, brown and red clays - coolibah) and Riverview (red earths - silver-leaved ironbark). The k values were significantly correlated with organic Chrease activity ratio (r = 0.99***) and reciprocal of clay content (r = 0.97**) of the virgin soils. In stepwise multiple regression analysis, aggregation index (for kc values) or exchangeable sodium percentage (for kw) and organic C/urease activity ratio of soils were significantly associated with the overall rate of loss of organic C. It was inferred, therefore, that the relative inaccessibility and protection of organic matter against microbial and enzymic attack resulted in reduced organic C loss. Losses of organic C from the deeper layers (0-0.2 m, 0-0.3 m) were observed in Waco, Langlands-Logie, Cecilvale and Riverview soils, although generally rate of loss decreased with depth.