bluuebunny/crossref_metadata_2025 huggingface dataset:
Degradation and restoration of soil structure in a cracking grey clay used for cotton production
Authors: Daniells IG
Published: April 2005

A field experiment involving irrigated cotton investigated the effect of tillage on a self-mulching cracking grey clay at three different soil water contents: dry (close to permanent wilting point to over 1 m depth), moist (subsoil close to the lower plastic limit) and wet (just trafficable). These treatments had been repeated over three years prior to the plant and soil measurements reported in this paper. Compared with tillage of dry soil, tillage of moist or wet soil depressed lint yield by 35% (P<0.001). Shrinkage curves of resin-coated, intact soil clods showed lower clod bulk density at a standard water content in the dry treatment than in the wet treatment (P<0.001). This difference was most marked in the 0.2-0.3 m depth, where clods from the wet treatment had a bulk density approaching that of clods made from hand-remoulded soil. Subsequent restoration treatments showed that, although wheat improved soil physical condition, the yield of a following cotton crop was reduced due to lower nitrogen uptake (P<0.001). Deep tillage alone increased clod bulk density but deep tillage after wheat decreased density (interaction P<0.001 for the 0.2-0.3 m depth, P<0.05 for the 0.3-0.4 m depth). These effects of deep tillage were not reflected in yield of cotton. Effects of the previous dry, moist and wet tillage treatments persisted but there was some improvement, even in the absence of restoration treatments. To preserve the structure and productivity of cracking clay soils, they should be tilled only when dry to permanent wilting point through the full depth of tillage.
Aspects of soil particle size analysis in Australia
Authors: Mctainsh GH , Duhaylungsod NC
Published: April 2005

Analysis of the particle-size characteristics of a soil can provide valuable information on the processes and products of soil formation. Studies of loess soils world-wide have used particle size as a major criterion, however, in Australia the particle-size characteristics of parna (a t y e of loess with a high clay content) have not been measured in detail. A modified method of particle-size analysis is proposed which gives more accurate results and which may contribute to a better understanding of soil formation in general, and loess formation in particular, in Australia.
Effect of cultivation on the relationship between root length density and unsaturated hydraulic conductivity in a moderately swelling clay soil
Authors: Prathapar SA , Meyer WS , Cook FJ
Published: April 2005

Few studies have examined the effect of cultivation on the relationship between the presence of roots and unsaturated hydraulic conductivity in the soil matrix. Roots change soil pore characteristics by modifying pore diameter and pore continuity. Thus, the presence of roots may be expected to affect the hydraulic conductivity in saturated and unsaturated phases. In situ measurements of unsaturated hydraulic conductivity (Ku) at 0.04 m suction and root length density (Lv) of a moderately swelling soil were made in a wheat field and in a natural pasture field at 0, 0.25 and 0.4 m depths to determine their inter-relations. The Ku value decreased significantly with depth and the surface layer of the wheat field had the highest value (0.28 m day-1). The pasture field had high Lv at the surface layer (7.3 cm cm-3), but values decreased to less than those in the wheat field at 0.4 m depth. There was a distinct positive correlation between Lv and Ku, with the slope of the linear regression line being greater in the wheat field than in the pasture field. The cause of the relation is probably due to the common pore characteristics which influence Ku and Lv.
Reducing phosphorus leaching from sandy soils with red mud bauxite processing residues
Authors: Vlahos S , Summers KJ , Bell DT , Gilkes RJ
Published: April 2005

This study used field lysimeters to investigate the reduction in the leaching of phosphorus (P) applied as superphosphate fertilizer from a very sandy Swan Coastal Plain soil treated with bauxite processing residue (red mud) neutralized with either waste gypsum from the phosphate industry or ferrous sulfate (copperas) from the titanium dioxide industry. Addition of 500 t ha-' red mud/gypsum or 200 t hap1 red mud/copperas were found to reduce the leaching of P to below 3 kg ha-l for application rates of 270 and 80 kgP ha-1, respectively. Water retention from these excessively well drained soils was increased by 14 and 50% by the addition of 200 and 2000 t ha-l red mud, respectively. The pH of the leachate for all rates of red mud/copperas application increased from approximately 4 to range between 7 and 7-5. The concentrations of Na and SO4 were about 8 and 17 g1-l, respectively, in the initial leachates collected from the 2000 t ha-' red mud treatment but declined to approximately 0.4 and 2.0g l-1 after 3 years of leaching. The Ca leaching appeared to be initially controlled by the solubility of the excess CaSO4 remaining after red mud neutralization, with concentrations ranging between 0.3 and 0.5 g l-1 before declining to approximately the levels for untreated soils of 0.01-0.06g l-1. The Na, So4 and Ca concentrations in the leachates from the 500 t ha-l red mud/copperas treated soil decreased to acceptable levels after 2 years. High total soluble salt (TSS) levels associated with high levels of residue application may affect pasture production in the years immediately following soil amendment
The effect of stubble management and N-fertilization practices on the nitrogen economy under intensive rice cropping
Authors: Bacon PE , Lewin LG , McGarity JW , Hoult EH , Alter D
Published: April 2005

The fate of 15N-labelled fertilizer applied to rice (Oryza sativa L) was studied in microplots established within two field experiments comprising a range of stubble levels, stubble management techniques, N application rates and times. The first experiment investigated uptake of soil and fertilizer N in plots where application of 0 or 100 kg N ha-1 to the previous rice crop had produced 11.5 and 16.1 t ha-1 of stubble respectively. The stubble was then treated in one of four ways-burn (no till); burn then cultivated; incorporated in autumn or incorporated at sawing. Microplots within these large plots received 60 kg ha-1 of 5% 15N enriched urea at sowing, just prior to permanent flood (PF), or just after panicle initiation (PI) of the second crop. The second experiment was undertaken within a field in which half of the plots had stubble from the previous three rice crops burned, while the other plots had all stubble incorporated. In the fourth successive rice crop, the two stubble management systems were factorially combined with three N rates (0, 70 or 140 kg N ha-1) and three application times (PF, PI or a 50 : 50 split between PF and PI). Nitrogen uptake and retention in the soil were studied within 15N-labelled microplots established within each of these large plots. Only 4% of the 15N applied at sowing in the first experiment was recovered in the rice crop, while delaying N application to PF or PI increased this to an average of 20% and 44% respectively over the two experiments. The doubling of N application rate doubled fertilizer N uptake and also increased uptake of soil N at maturity by 12 kgN ha-1. Three years of stubble incorporation increased average uptake of fertilizer and soil N in the second experiment by 5 and 12 kg N ha-1 respectively. In both experiments, the soil was the major source of N, contributing 66-96% of total N uptake. On average, in the fourth crop, 20% of fertilizer N was in the grain, 12% in the straw and 3% in the roots, while 23% was located in the top 300 mm of soil. A further 3% was in the soil below 300 mm. The remaining 39% was lost, presumably by denitrification.
The effect of pH, liming, moisture and temperature on the activity of nitrifiers in a soil under pasture
Authors: Bramley RGV , White RE
Published: April 2005

A short-term nitrification assay (SNA) was used to measure the activity of soil nitrifiers in the field in relation to soil pH and seasonal changes in soil temperature and moisture content. At roughly two-monthly intervals over two successive years, samples of the Tokomaru Silt Loam which had been limed in 1982 and/or 1987 were analysed in addition to an unlimed control. The SNA analysis was carried out for a range of pH values between 4.5 and 7.5, obtained by amending the incubation medium with small amounts of HCl or KOH. A quadratic curve was fitted to a plot of SNA value v, incubation pH. The fitted equations were used to calculate the pH optimum for nitrification (pHopt), the SNA value at pHopt (SNAopt) and the SNA value at the soil pH at sampling (SNApH). Values of pHopt and the mean soil pH over the year were higher in soil limed in 1982 than control soil; neither variable showed marked change in either soil over the first 320 days of observation. The addition of lime in 1987 raised the mean soil pH and pHopt in unlimed soil, but had negligible effect on either variable in soil limed five years previously. A covariance-type analysis demonstrated that the same quadratic equation could be fitted to each plot of SNA v. incubation pH for each soil treatment by changing the intercept parameter (C), i.e. the relationship between nitrifier activity and pH in the four soils remained constant over the year. No significant relationships could be found for the four soils between soil pH, pHopt, SNA, soil moisture content, soil temperature and C. However, the slight fluctuation in pHopt tended to follow the variation in soil pH. Values of SNAopt and SNApH showed a more obvious seasonal trend and showed a 1 : 1 relationship over a range of values from 0.015 to 0.110 �mol g-1 h-l; i.e. the nitrifier activity in the soil, irrespective of variations that were random (unknown influences) or associated with seasonal variables (temperature and moisture), was near the optimum with respect to pH. Nitrification activity is dynamic and changes quickly in response to changes in the soil environment. The implications of this with respect to nitrate leaching models include the likelihood that it may not be possible to produce a definitive model which works for all soil types.
The use of dispersible clays to reduce water repellency of sandy soils
Authors: Ma'shum M , Oades JM , Tate ME
Published: April 2005

Water-repellency in sandy soils is determined by the amount of hydrophobic organic matter coating the sand particles and the specific surface area of the sands. The hydrophobic state can be simulated by coating hydrophilic sand with cetyl alcohol. Admixture of finely particulate materials with either naturally occurring water-repellent sands or the model cetyl alcohol-coated sand markedly reduced the water-repellency. Dispersible sodic clays were more effective than calcium saturated clays in reducing water-repellency, suggesting that the addition of dispersible, fine-grained illites and kaolinites couid play an important role in the rapid control of water-repellent soils in field situations.
Limitations of EGME retention to estimate the surface area of soils
Authors: Tiller KG , Smith LH
Published: April 2005

The suitability of two procedures for the measurement of total surface area, based on 'the retention of ethylene glycol monoethyl ether (EGME), was investigated for a wide range of clay fractions and Australian soils. Experimental conditions for optimum precision and convenience of measurement were established. The procedures which utilized a higher vapour pressure of EGME achieved a higher retention of EGME by soils, reached the final condition of measurement more rapidly, and were less dependent on exchangeable cation status of the samples in confirmation of published work with pure smectite. The critical weakness of published procedures for soils is the assumption that the surface area occupied by an EGME molecule on a smectite reference sample can be applied to all soil surfaces. EGME retained per unit area by a range of soil and pure smectites, calculated from total surface area derived from crystal dimensions, and by a range of non-swelling minerals, related to measured BET-N2 areas, varied about fourfold between different mineral groups, and nearly twofold for different smectites. This variation could seriously over- or under-estimate estimates of total surface area, depending on the reference mineral chosen in relation to the mineral species being characterized. Alternatively, for soils free of clay minerals with internal surfaces, an empirical approach based on measured BET-N2 areas of representative soils may be feasible. A consideration of EGME retained in relation to BET-N2 areas may usefully complement X-ray diffraction procedures for characterizing randomly interstratified material in soil clay fractions.
Variability in characteristics of some acidic pasture soils in South Australia and implications for lime application
Authors: Merry RH , Tiller KG , Richards AF
Published: April 2005

The variability of soil pH (0.01 M CaCI2), aluminium and manganese (extractable in 0.01 M CaCl2), total carbon and some soil morphological factors have been investigated in the surface and subsoil at seven pasture sites in the southern Mount Lofty Ranges and Kangaroo Island, South Australia. The coefficients of variation of the factors measured were found to be of a similar order, except for soil pH which, being a logarithmic transformation, is much lower. Relationships between pH and soil aluminium, manganese and carbon are used to predict the effects of further acidification, especially with respect to the development of increased extractable aluminium, and to assess the likelihood of problems in selecting appropriate rates of lime application.
Effect of surface application of urea, ammonium-sulfate and lime on exchangeable cation distribution in an inceptisol in humid tropical Queensland
Authors: Gillman GP , Bristow KL
Published: April 2005

The effect of two sources of N (urea and ammonium sulfate) on the leaching of exchangeable cations in an Inceptisol was examined in the field over a 6 week period. During this time, artificial rainfall (60, 80 and 90 mm) was applied on three occasions to enhance the rate of leaching of exchangeable cations. This was assessed by taking soil samples prior to, and 2 days after, each irrigation. By the end of the experiment, about 50% of the applied N had been lost from the top 20 cm of the profile. Ammonium sulfate caused exchangeable cations to move from the 0-5 cm layer, but urea had no effect on cation distribution. The effects of lime application were confined to the upper 10 cm of the soil profile.
Occurrence of palygorskite in soils of Ecija (Spain)
Authors: Perez-Rodriguez JL , Maqueda C , Morillo E
Published: April 2005

Palygorskite has been characterized in soils classified as typic argixerolls, located in an extensive Quaternary zone in the north of Seville (Spain), where the geological and climatic conditions suggest its genesis. The soils contain a Ck horizon which has different textural characteristics to the other horizons in the profiles. The presence of large white calcareous nodules and cristobalite is the principal difference between them. The formation of palygorsltite at textural discontinuities is in agreement with the characteristics of these soils. Under the present conditions of the soils (pH, magnesium and silicon concentration and soluble salts), the alteration of palygorsltite to smectite is suggested. The sporadic nucleation of large fibres of palygorsltite on silica crystal suggests that this latter mineral could provide the necessary silicon for palygorsltite formation.
Laboratory simulation of the surface morphology of self-mulching and non-self-mulching vertisols .2. Quantification of visual features
Authors: Pillai-McGarry UPP , Collis-George N
Published: April 2005

Descriptions of the surface morphology of Vertisols presently use subjectively classed, descriptive attributes. A system to quantify the appearance of the soil structural components is required to allow the comparison of soils, and to determine effects of variation in climate and of chemical/physical ameliorants. A non-destructive method of quantifying surface structural features is presented. Ponded and puddled samples of the 0-20 mm surface layer of a self-mulching Vertisol and two non self-mulching Vertisols were subjected to either a continuous drying regime or a sequence of wetting/drying cycles. Structural development with time was assessed by quantifying structural features using photographs of the soil surface. With repeated wetting and drying the self-mulching soil developed crumb material, the smallest shrinkage blocks, and the widest cracks. The non self-mulching soils developed no crumbs and the cracks generally became narrower. The range of structural development in terms of 'good' to 'bad' self-mulching in the laboratory agreed with the soils' behaviour in the field. Within the range of experiments performed, puddled soils did not produce as 'good' a self-mulching surface as non-puddled soils, no matter how many drying/wetting cycles were carried out.
In situ neutron moisture meter calibration in lateritic soils
Authors: Ruprecht JK , Schofield NJ
Published: April 2005

An in situ calibration procedure for complex lateritic soils of the jarrah forest of Western Australia is described. The calibration is based on non-destructive sampling of each access tube and on a regression of change in water content on change in neutron count ratio at 'wet' and 'dry' times of the year. Calibration equations with adequate precision were produced. ever, there were high residual errors in the calibration equations which were due to a number of factors including soil water variability, the presence of a duricrust layer, soil sampling of gravelly soils and the variability of the cement slurry annulus surrounding each access tube. The calibration equations derived did not compare well with those from other studies in south-west Western Australia, but there was reasonable agreement with the general equations obtained by the Institute of Hydrology, U.K.
Solid-state CP/MAS 13C NMR analysis of particle size and density fractions of a soil incubated with uniformly labeled 13C-glucose
Authors: Baldock JA , Oades JM , Vassallo AM , Wilson MA
Published: April 2005

A soil incubated for 34 days in the absence (control) and presence (treated) of uniformly labelled 13C-glucose was dispersed using an ultrasonic probe and fractionated by sedimentation in water and a polytungstate solution of density 2.0 Mg m3 . The residual substrate carbon was concentrated in the clay and light fractions. Solid state CP/MAS 13C n.m.r. (cross polarization/magic angle spinning 13c nuclear magnetic resonance) spectroscopy was used to characterize the chemical structure of the native soil organic carbon and the residual substrate carbon in the fractions of the control and treated soils. To obtain quantitative results it was essential to determine the spin lattice relaxation times in the rotating frame, T1pH, of the individual carbon types in the spectra as the relaxation behaviour of the native organic materials in the clay fraction was substantially different from that of the residual substrate carbon. After correcting for T1pH effects, a significant linear relationship existed between the signal intensity and 13C content of the samples. This enabled the content, expressed in �mol 13C g-1 fraction, of each type of carbon in the fractions to be calculated. The residual substrate carbon was found to accumulate in predominantly alkyl and O-alkyl structures in both fractions. However, significant amounts of acetal and carboxyl carbon were also observed in the clay fraction. Little if any aromatic or phenolic carbon was synthesized by the soil microorganisms utilizing substrate carbon. Dipolar dephasing CP/MAS 13C n.m.r. experiments were also performed and allowed the proportion of each type of carbon which was protonated and nonprotonated to be estimated. Essentially all of the O-alkyl and acetal carbon, 25-40% of the aromatic carbon and 66-80% of the alkyl carbon was protonated in the fractions isolated from the treated soil
Solid-state CP/MAS 13C NMR analysis of bacterial and fungal cultures isolated from a soil incubated fith glucose
Authors: Baldock JA , Oades JM , Vassallo AM , Wilson MA
Published: April 2005

Bacteria and fungi were isolated from a sample of the Meadows fine sandy loam, an Alfisol, and selectively cultured in nutrient solutions at 20�C for 5 days. The bacteria and fungi were collected, washed with deionized water, freeze dried and analysed using conventional and dipolar dephased solid state CP/MAS 13C n.m.r. spectroscopy. To obtain a quantitative estimate of the chemical composition of the bacterial and fungal carbon, a recycle delay of 3.0 s was required to allow complete relaxation between pulses, and the acquired signal intensities had to be corrected for the amount of signal relaxation which occurred during the contact time (i.e. T1pH effects). The bacterial materials contained more alkyl and carboxyl carbon but less O-alkyl and acetal carbon than the fungal materials. Comparison of the composition of the bacterial and fungal carbon with that of the native and residual substrate carbon contained in the clay and light fraction of a sample of Meadows fine sandy loam incubated with 13C-glucose indicated that the soil microbial population was dominated by fungi.
Adsorption-desorption behavior of selected pesticides in some Western Australian soils
Authors: Singh R , Gerritse RG , Aylmore LAG
Published: April 2005

The adsorption-desorption behaviour of four pesticides, in four Western Australian soils differing in their physico-chemical properties, has been studied using a batch technique. Sorption data for Fenamiphos, Linuron and Simazine could be fitted to a Freundlich-type equation, while that for Diquat more closely fitted the Langmuir equation. The value of the exponent in the fitted Freundlich isotherms varied from 0.70 to 1.00 for the various pesticide and soil combinations. Adsorption was found to be better correlated with organic matter than other soil properties, and decreased with increasing pH for all pesticides except Diquat. This study supports the observation of B. T. Bowman that the Freundlich equation in mole fraction form is more useful for comparing relative adsorption. Comparison of the present adsorption data with previous studies showed that the organic matter in these soils behaved differently in terms of pesticide adsorption. In particular, the octanol-water partition approach, for predicting the adsorption of non-ionic organic compounds, gave unsatisfactory predictions of Linuron and Fenamiphos adsorption in these soils. Desorption by a consecutive method showed hysteresis with all pesticide-soil combinations examined. The magnitude of the hysteresis was unaffected by changes in the soil : solution ratio. Using a dilution method, experimental procedures such as centrifugation and shaking have been shown to only slightly affect desorption hysteresis. The suggestion that hysteresis results from organic matter effectively 'locking in' the adsorbed pesticides is supported. The presence of methanol in the desorption solution results in swelling of organic polymers and facilitates the release of the adsorbed pesticides. Consequently, hysteresis was found to be essentially absent from the Linuron isotherm on removal of organic matter from the soil.
Turnover of soil organic matter under pasture as determined by 13C natural abundance
Authors: Skjemstad JO , Lefeuvre RP , Prebble RE
Published: April 2005

The change in vegetation cover from rainforest with a C3 photosynthetic pathway to grasses with C4 pathways was used to follow input rates and turnover of organic matter in a krasnozem over an 83 year period. The measurement of 613c values on soils from three depths (0.0-7.5, 7.5-15.0, 60.0-80.0 cm) indicated that charcoal was a serious contaminant in the light fractions (<1.6 Mg mW3) of all samples and should be removed. Of the two grasses studied (Paspalum dilatatum and Pennisetum clandestinum), the latter gave more input of organic matter into the 7.5-15.0 cm horizon. In the other horizons, both grasses performed equally. Organic matter within microaggregates (<0.2 mm) proved to contain up to 32% more old carbon than the remaining soil after 83 years. Turnover times for organic matter in the >1.6 Mg m-3 fraction from the three depths were calculated as 60, 75 and 276 years respectively, compared with 75, 108 and 348 years for the organic matter within microaggregates from the same horizons. It is concluded that the presence of microaggregates is an important factor in stabilizing organic matter in this soil type. Some difficulties with the technique are also discussed.
Allophane in New Zealand - a review
Authors: Parfitt RL
Published: April 2005

Studies of allophanes from New Zealand are reviewed, and a definition of the allophane group of minerals is suggested. Three types of allophane are identified, and their structures are discussed under headings Al-rich soil allophanes, Si-rich soil allophanes and stream deposit allophanes. Examples from New Zealand soils and tephras are discussed in relation to properties, identification and weathering processes.
Predicting yield responsiveness and phosphorus fertilizer requirements of soybeans from soil tests
Authors: Moody PW , Dickson T , Dwyer JC , Compton BL
Published: April 2005

Field experiments with rain-fed Bragg soybeans (Glycine max) were carried out at 30 sites in central south-eastern Queensland over six years. The sites covered a wide range of soil types and P buffer capacities. Several rates of P fertilizer were band-applied in 0.9 m rows at planting. Relative grain yield at each site was correlated with 0.5 M NaHC03 extractable (PB) and 0.01 M CaCl2 extractable (PC) phosphorus. Mitscherlich equations of best fit indicated that PC was better correlated (r2 = 0.85) with relative grain yield than PB (r2 = 0.59). At 90% maximum grain yield, the 'critical' PC value was 43 �g P kg-1. The Mitscherlich curvature coefficient, c, was correlated (r2 = 0.49, P < 0.001) with the amount of P fertilizer required for 90% maximum grain yield, but not with soil P buffer capacity, as measured by a single point sorption index (r2 = 0.06). Factors other than the P sorbing ability of the soil were affecting the curvature coefficient, but could not be identified in this work. PC was sufficiently well correlated (r2 = 0.66, P < 0.001) with P fertilizer requirements to have use as a predictor of these requirements. The findings are compared with those obtained for other crops and P fertilizer application methods.
Use of the EM-34 instrument in groundwater exploration in the Shepparton region
Authors: Potts IW
Published: April 2005

Since the late 1970's, the Rural Water Commission of Victoria (RWC) has been offering a groundwater exploratory drilling service to landholders in the irrigation areas of the Shepparton Region. The aim of this service has been to encourage exploration for shallow aquifers in the Shepparton Formation and in turn to encourage groundwater pumping for water-table control. The selection of drilling sites in early exploration programs was based on geomorphological expressions of prior stream activity. Later, the dipole-dipole resistivity survey method was used. While giving good resolution of targets in the sedimentary profile, this method was found to be too restrictive in covering large areas of a property. In 1986, the RWC acquired a Geonics EM-34 unit to become the main geophysical tool in groundwater exploration. Since this time, the unit has been used on over 60 individual properties, as well as being used for broader scale exploration surveys on the Riverine Plains. The EM-34 unit has proved to be a useful tool in defining areas where shallow sand aquifers occur in the Upper Shepparton Formation. The RWC uses the horizontal dipole technique with a constant coil separation of 20 m. This technique has allowed good line coverage of up to 7500 m in a day, while allowing fair resolution of the target within the top 15-20 m of the Shepparton Formation. Experience has shown that a number of non-rigorous categories can be applied to the various ranges of conductivity readings. Such categories aid in the interpretation and selection of drilling targets.
Estimating solution extract salinity from soil paste electrical conductivity - an evaluation of procedures
Authors: Slavich PG , Petterson GH
Published: April 2005

The electrical conductivity (EC) of a saturated soil paste extract (ECe) is the standard soil salinity measurement used to assess plant salt tolerance. Recently, a less time consuming method for the laboratory measurement of ECe was proposed that estimates ECe from EC measurements made directly in the saturated soil paste (ECp). The method uses a soil EC model and two empirical relationships developed with American soils. The empirical relationships are used to estimate the surface charge component of EC (ECs) and the water content of the continuous liquid current flow pathway (Bwc) from the saturation percentage (SP). This paper demonstrates that the same method may be successfully applied to Riverine Plain soils of S.E. Australia. The empirical relationships determined with Riverine Plain soils differed slightly from those published for American soils and gave a small improvement in accuracy. The method reduces the labour requirement of ECe measurements by approximately half.
Seasonal storage and release of phosphorus and potassium by organic matter and the microbial biomass in a high producing pastoral soil
Authors: Perrott KW , Sarathchandra SU , Waller JE
Published: April 2005

Seasonal and fertilizer effects on forms of soil phosphorus and potassium, partially decomposed organic debris and enzyme activities were studied over 2 years on a highly fertile yellow-brown loam (Typic Vitrandept) under grazed pasture. Fertilizer topdressing (potassic superphosphate) increased total inorganic phosphorus, NaHCO3-extractable inorganic phosphorus and NaHCO3- extractable potassium, but did not affect organic forms of phosphorus, microbial biomass potassium and phosphorus, or organic debris. Labile organic phosphorus (extracted by NaHCO3), microbial phosphorus and potassium, and organic debris accumulated over winter and declined in spring. Inter-year differences in climatic factors appeared to influence this basic pattern. Amounts of phosphorus released from labile organic and microbial phosphorus during spring were large (totalling 29 kg P ha-1 in one year) and could contribute substantially to plant P requirements. Mechanisms are proposed to explain the observed seasonal patterns in these soil characteristics. These include changes in the relative amounts of the fungal and bacterial components of the soil biomass during winter, mineralization of labile PI in spring due to increased bacterial growth and activity promoted by plant growth, and the subsequent release of P and K from the microbial biomass as a result of bacterial 'grazing' by protozoa.
Soil erosion processes and nutrient loss. 1. The interpretation of enrichment ratio and nitrogen loss in runoff sediment
Authors: Palis RG , Okwach G , Rose CW , Saffigna PG
Published: April 2005

The ratio of nutrient concentration in eroded sediment to that in the original soil (the enrichment ratio, ER) commonly varies with the accumulated soil loss. The objective of this study was to investigate possible factors contributing to this change in ER when erosion was accompanied by a significant depth of water. The enrichment ratio was directly measured on sediment from a sandy clay loam soil. ER was followed as a function of time for eight erosion experiments in which the mix of erosion processes and the fractional surface cover was varied. By using a simulated rainfall tilting flume facility, experiments covered low slope (0.1%), when rainfall detachment was the only erosion process, and 3% soil surface slope, where the processes of rainfall detachment and entrainment occurred. The type and extent of fractional surface cover was varied for the experiments with the 3% slope. In all cases, the rainfall rate was 100 mm h-1and the drop size was 2.2 mm. A new analytical framework is described, showing that ER can be interpreted from the product of two component distributions. The first component distribution is the concentration of sediment as a function of sediment size (a distribution found to vary with time and mix of erosion processes). The second distribution is nitrogen concentration (largely organic) as a function of size (found to be much less time-variable than sediment size). The conclusions reached, after analysis of these experimental data by using this framework, were: (i) time variation in ER was largely due to time variation in the first component distribution; (ii) values of ER different from unity require some variation with sediment size (or settling velocity) in the concentration of the nutrient sorbed to the soil or closely associated with the soil organic matter; (iii) the more that rainfall detachment dominates runoff erosion as the major erosion process, the more likely it is that ER is greater than unity.
A quick and simple method for determining the titration curve and estimating the lime requirement of soil
Authors: Barrow NJ , Cox VC
Published: April 2005

We investigated the effects of time and temperature of incubation on the pH of soil to which acid or alkali had been added. Most of the change in pH occurred quickly, but a slow reaction continued for a long period. The rate of this slow reaction was increased by increasing the temperature. The magnitude of the effect suggested that the continuing reaction was due to diffusion of protons into, or out of, the soil particles. Because of the increased rate of reaction at high temperature, it is possible to produce in a few days at 60�C effects similar to several months' incubation at 25�C. This provides a simple means of determining the titration curve and of estimating the lime requirement.
Lime requirement of acidic Queensland soils. I. Relationships between soil properties and pH buffer capacity
Authors: Aitken RL , Moody PW , Mckinley PG
Published: April 2005

The pH buffer capacity of 40 acidic surface soils (pHw <6.5) was determined from soil-CaCO3- moist incubations. Buffer capacity values ranged from 02 to 5.4 g CaCO3 kg-1 soil unit-1 pH increase. Organic carbon, clay content, ECEC, 1M KCl extractable acidity and Al, and the change in CEC with pH (�CEC) were measured and correlated with pH buffer capacity. Step-up multiple linear regression indicated that the effect of �CEC on buffer capacity was highly significant (r2 = 0.77, P <0.001), whereas that of exchangeable Al or exchange acidity was not. This suggests that deprotonation reactions, compared with exchangeable Al or exchange acidity, are considerably more important in determining buffer capacity. The major soil property affecting �CEC in our soils was the organic carbon content and, when step-up multiple linear regression was used, �CEC could be best estimated by organic carbon plus clay content plus ECEC (R2 = 0.77, P < 0.001). To ascertain whether exchangeable Al (or exchange acidity) would contribute to buffer capacity in soils with less variable charge, soils of relatively low organic carbon (<2.5%) were considered. For the 33 soils with <2.5% organic carbon, �CEC was still the major determinant of buffer capacity (r2 = 0.76, P <0.001), although inclusion of exchange acidity in a multiple regression with �CEC significantly increased the variance accounted for (R2 = 0.80, P < 0.001). Of the soil properties that could be routinely measured, a multiple regression equation combining organic carbon, clay content and exchange acidity accounted for 85% of the variance in buffer capacity, with organic carbon being the most important.
Lime requirement of acidic Queensland soils.II. Comparison of laboratory methods for predicting lime requirement
Authors: Aitken RL , Moody PW , Mckinley PG
Published: April 2005

A number of laboratory procedures for predicting lime requirement were evaluated by using 40 acidic surface soils from eastern Queensland. The methods were compared on the basis of their ability to predict the lime requirement to pHw values of 5.5 and 6.5 obtained from soil-CaCO3-moist incubations. The laboratory methods evaluated included 1M KC1 extractable Al, equilibration of soil : water suspensions with varying amounts of added Ca(OH)2, the Shoemaker, McLean and Pratt (SMP) single-buffer method, the SMP double-buffer method, the Yuan double-buffer method and the Mehlich single-buffer method. Aluminium extracted ,with 1M KCl was a poor predictor of lime requirement to pH, 5.5. In most of the soils tested, the actual amounts of lime required to reduce Al to a predetermined level far exceeded those calculated on the basis of 1 M KCl extractable Al values of untreated soils. Batch equilibration of soil : water suspensions containing Ca(OH)2 proved a reliable but relatively time-consuming method of determining lime requirement. All of the buffer methods were reasonably well correlated with lime requirement (0.61 < r2 < 0.82). Buffer methods which had a high initial buffer pH and a relatively high buffer strength were less well correlated with lime requirement than weaker buffers of lower initial pH. The Mehlich single-buffer method (initial pH 6.6) fitted both these latter criteria and gave good correlations with lime requirements to pHw 5.5 (r2 =0.78) and pHw 6.5 (r2 = 0.80). Compared with the single-buffer methods, neither of the double-buffer methods (which require two pH measurements) was better correlated with lime requirements.
Soil respiration in the seasonally dry tropics near Townsville, North-Queensland
Authors: Holt JA , Hodgen MJ , Lamb D
Published: April 2005

The contribution of root respiration to total soil respiration has been examined in an Australian tropical semi-arid woodland. Respiration rates were estimated by measuring CO2 released from untreated soil and from soil where roots had been severed and were extensively decomposed. The amount of C released as CO2 by soil respiration was estimated to be 3800 kg ha-1 year-1, and by root respiration to be 1500 kg C ha-l year-1. Soil moisture was found to have a major effect on soil respiration, with temperature being less significant. Consequently, most respiratory activity in the soil was confined to the relatively short wet season, with respiration rates being much lower during the dry season.
The effects of fire on the soil in a degraded semiarid woodland .I. Cryptogam cover and physical and micromorphological properties
Authors: Greene RSB , Chartres CJ , Hodgkinson KC
Published: April 2005

The effects of fire on the cryptogam cover and physical and micromorphological properties of a massive red earth soil were studied in a semi-arid eucalypt woodland, heavily invaded by shrubs, near Coolabah, N.S.W. Fire reduced the cryptogam cover and concomitantly increased the depositional material produced by erosion and the area of bare surface. Annual fires for 7 years completely destroyed the cryptogamic crusts, but they recovered slowly in the absence of fire to reach the same cover as unburnt areas after about 4 years. A single fire also caused a major decline in aggregate stability of the 0-1 cm horizon, possibly because of alteration of organic cementing materials which consist of gels secreted by algae. Micromorphological observations of surface crusts showed that, as the frequency of fire increased, there was more depositional material produced by erosion coupled with the presence of thin laminated deposits. There was also less surface irregularity, fewer algal gels and less evidence of soil mixing by soil fauna. There was a significant negative relationship between the saturated infiltration rate and the number of fires (r2 = 0.63, P = 0.05). However, there was no effect of fire treatment on the unsaturated infiltration rate measured at a supply pressure of -40 mm, at which pores >0.75 mm diameter are excluded from water flow. In our burned plots, the rate of recolonization by cryptogams was relatively fast and, with approximately 4 years recovery, cryptogam cover reached the level of unburned controls. This cryptogam cover is critical in maintaining the physical properties of the soil. It is concluded, therefore, that irregular fires in this land system will not result in a permanent decline in the physical properties of the soil.
Correction
Authors: Moody PW
Published: April 2005

Corrigendum
A soil technical classification system for Pinus radiata (D. Don) plantations. I. Development
Authors: Turner J , Thompson CH , Turvey ND , Hopmans P , Ryan PJ
Published: April 2005

A technical classification system for soils of Pinus radiata plantations is presented. The soil attributes used were mainly from published data and classes were established on an a priori basis from information and experience of plantation forestry with this species. The system is designed for field use and does not require laboratory analyses; it uses factors that are not affected by the presence of the forest species; the classes are coded so as to produce data suitable for computerized information systems. The attributes used are parent rock, texture profile, depth to and nature of any impeding layer, texture and condition of the uppermost 10 cm of soil, character of surficial horizons according to paler subsurface or exposed subsoil, and the condition and colour of the subsoil. A parent rock classification has been devised according to soil-forming potential; this reduces rock identification to 12 main classes so as to facilitate field recognition. The classification is aimed at assisting soil-based silvicultural management of P. radiata forests, providing a basis for transferring technology between forests, and at accumulating specific resource information for inclusion in forest management information systems.
A soil technical classification system for Pinus radiata (D. Don) plantations. II. A basis for estimation of crop yield
Authors: Turvey ND , Booth TH , Ryan PJ
Published: April 2005

The Technical Classification is a system for encoding soil attributes according to parent rock; texture profile; depth to and type of impeding layer; texture, condition, and weathering of surface horizons; and nature and colour of the subsoil. The encoded data may then be used as a basis for soil-based silvicultural management decisions, such as prediction of wood yield, fertilizer prescription, thinning schedules, trafficking for off-road equipment, and placement of roads. The objective of this paper is to examine the suitability of the classification as a basis from which to estimate the yield of wood from Pinus radiata plantations. Data were collected from trees and soil profiles on 181 sites in New South Wales, South Australia, Victoria and Tasmania. All but one of the attributes (texture profile) of the Technical Classification were significantly related to wood volume as single factors at the 5% level of significance. The combined effect of soil attributes in explaining the variation in wood volume across the sites was analysed by backward stepwise elimination of variables from a multiple analysis of variance model. When summed, the parameter estimates for each soil attribute gave an estimate of wood volume produced at age 11 years. The model included the attributes: parent rock, soil depth, impeding layer, texture of surface soil, surface condition, and an interaction between texture profile and weathering of surface soil horizons. The attributes subsoil texture and subsoil colour were not significant in explaining the variation in wood volume in the data set under test. The model accounted for 75% of the variation in wood volume. The addition of rainfall did not improve the variation accounted for by the model. By comparison, the Great Soil Group classification accounted for 32% of variation in wood volume. The Factual Key classification at the level of principal profile form accounted for 53% of the variation in wood volume. We conclude that the Technical Classification is suitable as a basis from which to estimate the yield of wood from Pinus radiata plantations.
Influence of environmental conditions and some soil chemical properties on the carbon and nitrogen contents of some tropical Australian rainforest soils
Authors: Spain AV
Published: April 2005

Concentrations of carbon, total nitrogen, total phosphorus, soil pH, the sum of the exchangeable basic cations, clay and dithionite-extractable iron were examined in the surface soils of 72 rainforest sites from north-eastern tropical Queensland. Soils derived from basalt had higher levels of most of the above properties than those formed on other parent materials. Differences between the carbon status of soils formed from basalt and those formed from other parent materials may be related to the higher free iron levels and phosphorus status of the former group. Excluding the soils of basalt origin, both carbon and nitrogen are positively related to clay content. In contrast, within the soils of basaltic origin, carbon concentrations are negatively related to clay contents through interactions with free iron oxides. Separate univariate regression relationships were established between carbon and nitrogen concentrations and site temperature and precipitation for soils derived from basaltic and combined granitic and acid volcanic parent materials. Coefficients relating both nitrogen and carbon to temperature differed between these groupings. The importance of topography in controlling carbon levels is demonstrated in soils that are poorly drained or formed on ridges, while the importance of soil age is demonstrated by a juvenile soil formed on weakly weathered basalt.
The effect of preferential flow of dairy cow urine and simulated rainfall on movement of potassium through undisturbed topsoil cores
Authors: Williams PH , Hedley MJ , Gregg PEH
Published: April 2005

Cores of undisturbed topsoil (15 cm in depth and diameter) were taken from a range of soil types to a controlled climate chamber. Urine from dairy cows was spiked with tritiated water (3H2O) and then applied to these cores which had moisture contents near field capacity. Liquid draining from these cores, as a direct consequence of urine application, contained up to 72% of the tritiated water, 74% of the potassium (K), 62% of the nitrogen (N) and 80% of the chloride (Cl) applied in the urine, indicating that urine could flow preferentially beyond the 15 cm depth in these soils. The activity of tritium and the concentrations of K, N and Cl in the effluent indicated that this preferential movement of urine occurred too quickly for sorption reactions to occur between the soil surface and the majority of solutes in the urine. After preferential flow had ceased, the amounts of K leached by subsequent simulated rain events were much smaller than losses immediately following the urine application. Leaching losses were particularly small (accounting for 3-15% of the applied urine K) when the majority of the rain water moved preferentially through the soil cores, thus bypassing the urine K which was in soil micropores or which had been sorbed by the soil. Overall, these results suggest that substantial movement of K (and N) through the topsoil of grazed pastures may occur following a urination event due to preferential flow of dairy cow urine through the soil profile, at least when soils are near field capacity at the time of urine deposition. The extent of this movement through topsoil will be more dependent upon soil structural characteristics rather than soil chemical characteristics.
Corrigenda - Soil compaction and cotton growth on a vertisol
Authors: Mcgarry D
Published: April 2005

Differences in growth, yield and root systems of two adjoining cotton crops on a Vertisol near Dalby, Queensland, were explained in terms of soil profile morphology and soil shrinkage indices. The soil beneath the strongly inferior crop had platy structure in the 0.05-0.28 m layer and significantly less air-filled specific pore volume in the 0.2-0.4 m layer. This soil structure degradation was caused by seedbed preparation of wet soil, prior to sowing the cotton crop.