bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of drainage on characteristics of some soils of the Orkney Islands
Authors: Naidu R , Mitchell BD , MacKenzie RC
Published: April 2005

Three soil profiles with different degrees of drainage impedance developed on glacial till derived from Middle Old Red Sandstone sediments in the Orkney Islands were characterized texturally, chemically and mineralogically. Particular features of these soils were the high organic matter contents (9-50%) of the surface horizon soils resulting from high rainfall and cool temperatures. The high exchangeable Na+ and K+ contents in surface horizons of two of the pedons are a result of salt spray. The clay mineralogy and the nature and amount of aluminosilicate gel were affected by drainage class. In general, chlorite dominates the clay fraction of the imperfectly drained soil. However, with increasing impedence it was gradually displaced by mica which ultimately predominates in the very poorly drained saline gley. Vermiculitization occurred in the better drained soils. The poorly drained soils were distinguished by the absence of chlorite. Goethite was present in all soils but lepidocrocite occurred only when drainage was strongly impeded. Hematite was never present in these soils.
The bioturbation activity of ants in agricultural and naturally vegetated habitats in semiarid environments
Authors: Debruyn LAL , Conacher AJ
Published: April 2005

The effect of ant activity on bioturbation rates was assessed in the central wheatbelt of Western Australia in naturally vegetated and farmland sites, by bimonthly measurements of soil fauna activity and periodic measurements of ant nest dimensions. The percentage soil surface affected by soil fauna (%SSASF) was on average 0.5%, with the lowest activity in cropped areas and the highest %SSASF recorded in pasture sites (>2%). Overall %SSASF was greater on yellow sand in comparison with grey sandy loam. The estimated bioturbation rates of ant communities in naturally vegetated and farmland habitats on both soils ranged from 10 to 37 g m-2 yr-1. On average, the amount of soil excavated by ants to build a nest was 20 to 25 g. Aphaenogaster sp. D49 was identified as a significant contributor to soil turnover based on the frequency of excavation, nest density and mass of soil removed to build the nest (134 g). Aphaenogaster sp. D49 brought to the soil surface 465 g m-2 yr-1 on grey sandy loam and 223 g m-2 yr-1 on yellow sand. The activity period for the majority of ant nests was around 3 months, but some species such as Rhytidoponera spp. and Meranoplus spp. had nests active for up to 2 years. While other ant species such as Iridomyrmex sp. D13 have a high turnover of nests (<3 months). There was no clear seasonal trend in the number of active nest openings, although they appeared to be greatest in May, and lowest in January. Ant nest density was higher in yellow sand than in grey sandy loam, regardless of land use. Particle size distribution of ant spoils (soil brought to the surface during nest construction) and ant-affected soil at 26 cm was compared to the control soil at comparable depths, and found to be similar. Three instances where the ant spoil had a higher proportion of clay-sized particles in comparison with the control soil, and this was attributed to ants excavating into the clay subsoil or being size-selective in the material they excavated. The control soil had a texture-contrast between 2 and 26 cm, while all the ant nests examined had similiar texture between these two depths. This supports the hypothesis that ant activity homogenizes the soil texture profile.
Structural amelioration of a South Australian red-brown earth using calcium and organic amendments
Authors: Baldock JA , Aoyama M , Oades JM , Susant o , Grant CD
Published: April 2005

The ability of wheat straw, gypsum and agricultural lime to ameliorate the unstable structural condition of a degraded red-brown earth located at the Waite Agricultural Research Institute, South Australia, was investigated in a field experiment lasting 5 years. Wheat straw was added at rates of 0, 5 and 10 t ha-1 y-1, and gypsum and agricultural lime were added at rates of 3.4 and 2.0 t ha-1 y-1 respectively. Most of the measurements were taken on samples collected after three and four consecutive years of treatment applications, but some were taken one year after the fifth and final application of the treatments. The amount of water-stable macroaggregation in the top 10 cm increased with increasing rate of wheat straw application. Addition of agricultural lime incorporated with straw temporarily increased macroaggregate stability to a greater extent than was observed with either amendment alone. The proportion of the soil surface occupied by macropores was also increased significantly by addition of agricultural lime, and this was attributed to a stimulation of biological activity in the soil due to the increased soil pH. Density fractionation of the soil suggested the turnover of the added wheat straw in the lime-treated soil was greater than in the gypsum-treated and control soils. Addition of gypsum decreased the content of mechanically dispersible clay by modifying the electrolyte concentration and composition, but was unable to completely resist the dispersive tendencies created by the decomposing organic residues. The high rates of wheat straw incorporated in the top 10 cm caused significant dispersion in the top 20 cm, which was thought to have mobilized clay particles causing them to move downward, resulting in pore blockage and the consequent lowering of hydraulic conductivity in the zone immediately below.
Effect of water salinity on inter-rill erosion and infiltration - Laboratory study
Authors: Agassi M , Shainberg I , Vandermerwe D
Published: April 2005

The effect of water salinity on inter-rill erosion and infiltration rate was studied using six soils from South Africa. The soils were subjected to simulated rainstorms (22.3 J mm-1 m-2) using three water salinities (electrical conductivity) of 0.01, 0.7 and 2.5 dS m-1, respectively. The soils were divided into stable and unstable soils, depending on their susceptibility to erosion processes and seal formation. In general, infiltration rate increased and runoff and erosion decreased with increasing water salinity, for the unstable soils, while with the stable soils, water salinity had no effect, or even deleterious effects, on infiltration rate and erosion. A very high correlation was found between final infiltration rate and erosion for all the soils and water salinities.
Field-evaluation of DRAINMOD for predicting waterlogging intensity and drain performance in South-Western Australia
Authors: Cox JW , Mcfarlane DJ , Skaggs RW
Published: April 2005

Waterlogging is common on sloping duplex soils in south-western Australia and causes damage to non-irrigated cereal crops and pastures. The factors which affect the performance of surface seepage interceptor drains installed to reduce this waterlogging are complex because the soils are very variable and have preferred pathways for groundwater flow. We compared DRAINMOD's predictions with field measured waterlogging intensity and drain flow over 3 years near Mt Barker and Narrogin in Western Australia. DRAINMOD failed to accurately predict waterlogging intensities and drain flows because water can move through macropores which bypass the soil matrix. At Mt Barker, DRAINMOD overpredicted waterlogging intensity by between 120% in a wet year and 650% in a very dry year. Drain flows were underpredicted by 148% in the driest year. At Narrogin, DRAINMOD underpredicted waterlogging intensity each year (rainfall was below average each year) and drain flow in the driest two years. However, by increasing Ks of the topsoil and adjusting Ks of the subsoil clay, DRAINMOD predictions agreed with measured responses. DRAINMOD can be used to predict waterlogging intensities and drain flows in duplex soils in the >450 mm annual rainfall areas of south-western Australia provided adjustments are made to the field point-measured Ks. Reliability increases with increasing rainfall during the growing season.
A method for measuring aggregate water stability of dryland soils with relevance to surface seal development
Authors: Loch RJ
Published: April 2005

This paper examines the potential for a test of aggregate stability-or more correctly, of the water-stable size distributions resulting from wetting-to be correlated with surface seal development and infiltration of rainfall under field conditions. Aspects of measurement of water stable aggregation considered include wetting method, sample depth, area, antecedent water content, and the use of whole soil rather than restricted dry aggregate size ranges, and the water stable size fractions likely to restrict water entry and form surface seals. From consideration of pore sizes likely to prevent direct entry of raindrops into the soil, it is concluded that surface seal development is likely to be related to the proportion of particles <100 �m. For the northern cereal growing areas of eastern Australia, essential features of a method for studying aggregate stability of dryland soils are: (a) wetting of air-dry soil by simulated rain with kinetic energy close to 29 J m2 mm-1 and intensities of 85-100 mm h-1 for at least 20 min; (b) the wetting applied to field or laboratory plots of 'whole soil' rather than selected dry aggregate sizes, with plots at least 0.36 m2 in area, and laboratory plots being approximately 100 mm deep; (c) samples of the compacted surface layer under high energy rain (to a depth of 3-5 mm) taken with a spatula; (d) size distribution measured by sieving in tap water using a modified Yoder wet sieving apparatus, a nest of sieves with minimum aperture of 0.125 mm, and material passing through the finest sieve collected and weighed; no distinction being made between aggregates and primary particles. Subsequent papers will deal with validation of the proposed test and its use to consider effects of tillage management on water stability.
Measurement of aggregate breakdown under rain - Comparison with tests of water stability and relationships with field measurements of infiltration
Authors: Loch RJ , Foley JL
Published: April 2005

This paper reports comparisons between aggregate breakdown on wetting by rainfall with breakdown measured by a range of alternative methods. It also reports correlations between measured breakdown and steady infiltration rates of simulated rain of high and low energy, and hydraulic conductivities of surface seal layers formed under high energy rain. A wide range of soils in eastern Australia were studied. Highly significant correlations were found between measurements of aggregate breakdown to < 125 �m caused by rainfall wetting and both steady infiltration rates and hydraulic conductivities. Significant, but poorer correlations were found between steady infiltration rates and breakdown resulting from immersion wetting. Deletion of swelling soils from the data set greatly improved correlations between steady infiltration rates of high energy rain and breakdown measured by both immersion and tension wetting, showing that these methods of wetting ace particularly inappropriate for swelling soils. No correlation was found between infiltration rates and measured clay dispersion. Different relationships between the proportion of particles (%) < 125 �m at the soil surface (P125) and steady infiltration rates of low and high energy rain indicated that compaction of the soil surface layer, rather than increased aggregate breakdown, is a major cause of surface sealing by raindrop impacts. Measurements of fall cone penetration confirmed that drop impacts had compacted the surface layer. Suctions across the surface seal were related to P125 in that layer, and the relationship obtained was used in calculating hydraulic conductivities. The results confirm that measurement of aggregate breakdown under rainfall wetting produces results of much greater relevance to soil behaviour under field conditions than do tests based on immersion and tension wetting.
Amelioration of subsurface acidity in sandy soils in low rainfall regions .1. Responses of wheat and lupins to surface-applied gypsum and lime
Authors: Mclay CDA , Ritchie GSP , Porter WM
Published: April 2005

Amelioration of subsoil acidity using gypsum (CaSO4.2H2O) or lime (CaCO3) was studied on sandy textured soils with low water holding capacity in a low rainfall environment. Field trials were established in 1989 at two sites on yellow sandplain soils to investigate whether different rates, sources and combinations of gypsum and lime application could be used to increase wheat and lupin yields. Gypsum increased wheat yields by up to 45% in the first two growing seasons whereas lime increased wheat yields by up to only 15% in the second season. The highest yields were generally recorded when gypsum and lime were applied together. The response of wheat to the various treatments varied both regionally and temporally and it is suggested that the inherent soil solution composition affected the magnitude and rapidity of wheat responses to gypsum. The rate of gypsum application affected the longevity of the wheat responses, with a low application rate (1 t ha-1) increasing yields for only one season. No differences in wheat yields were recorded between different sources of gypsum or application rates higher than 3 t ha-1. In contrast to wheat, lupin yields were substantially lower on gypsum-treated plots. The yield decline did not appear to be related to any simple nutritional factor and the gypsum effect was generally minimized when lime was added with the gypsum. The results indicated that lower rates of gypsum than used in previous subsoil amelioration studies were suitable for increasing wheat yields on sandy soils in low rainfall environments, and that gypsum should not be used if lupins are to be grown within at least 2 years of its application to the soil surface.
Amelioration of subsurface acidity in sandy soils in low rainfall regions .2. Changes to soil solution composition following the surface application of gypsum and lime
Authors: Mclay CDA , Ritchie GSP , Porter WM , Cruse A
Published: April 2005

Two field trials were sampled to investigate the changes to soil solution chemical properties of a yellow sandplain soil with an acidic subsoil following the application of gypsum and lime to the soil surface in 1989. The soils were sandy textured and located in a region of low annual rainfall (300-350 mm). Soil was sampled annually to a depth of 1 m and changes in soil solution composition were estimated by extraction of the soil with 0.005 M KCl. Gypsum leaching caused calcium (Ca), sulfate (SO4) and the ionic strength to increase substantially in both topsoil and subsoil by the end of the first year. Continued leaching in the second year caused these properties to decrease by approximately one-half in the topsoil. Gypsum appeared to have minimal effect on pH or total Al (Al-T), although the amount of Al present as toxic monomeric Al decreased and the amount present as non-toxic AlSO+4 ion pairs increased. Magnesium (Mg) was displaced from the topsoil by gypsum and leached to a lower depth in the subsoil. In contrast, lime caused pH to increase and Al to decrease substantially in the topsoil, but relatively little change to any soil solution properties was observed in the subsoil. There was an indication that more lime may have leached in the presence of gypsum in the first year after application at one site. Wheat yields were best related to the soil acidity index Al-T/EC (where EC is electrical conductivity of a 1:5 soil:water extract), although the depth at which the relationship was strongest in the subsoil varied between sites. The ratio Al-T/EC was strongly correlated with the activity of monomeric Al species (i.e. the sum of the activities of Al3+, AlOH2+ and Al(OH)+2 in the soil solution. An increase in the concentration of sulfate in the subsoil solution (which increased the ionic strength, thereby decreasing the activity of Al3+, and also increased the amount of Al present as the AlSO+4 ion pair) was probably the most important factor decreasing Al toxicity to wheat. The results indicated that gypsum could be used to increase wheat growth in aluminium toxic subsoils in sandy soils of low rainfall regions and that a simple soil test could be used to predict responses.
Colour plates - Interpretation of soil features produced by ancient and modern processes in degraded landscapes .1. A new method for constructing conceptual soil-water-landscape models
Authors: Fritsch E , Fitzpatrick RW
Published: April 2005

A pedo-hydrological method which involves interpreting features in soils that result from both ancient and modern processes along toposequences in a subcatchment of the Mt Lofty Ranges, South Australia, is used to construct conceptual soil-water-landscape models. This method links soil-landscape features to soil-water processes with strong emphasis on: (i) soil water-flow systems and (ii) soil-forming and soil-change processes. The conceptual model illustrates the interactions between soil processes acting in soil water-flow systems. This model is able to predict future modes of soil-landscape evolution under changing environmental conditions. As well, it may be used by land and water supply managers to develop more efficient management strategies under conditions of increasing land degradation (e.g. erosion and water pollution). A typical Palexeralf-Natraqualf hydro-toposequence of soils (i.e. catena consisting of red-yellow-grey duplex soils) is used as an example to illustrate this new approach. The landscape selected is undergoing severe soil degradation (i.e. waterlogging, dryland salinity, erosion and water pollution). The constructed conceptual soil-water-landscape model is the result of detailed pedo-hydrological investigations along toposequences in a representative subcatchment in the high rainfall zone (>600 mm) of the Mount Lofty Ranges, South Australia. The model illustrates in graphic form interactions between three soil water-flow systems (freely drained red soil system, hydromorphic topsoil system, hydromorphic subsoil system) and eight soil processes (saprolitization, ferralitization, glaebulization, redoximorphism, eluviation/illuviation, salinization/solonization, sulfidization/sulfuricization and water erosion). The study demonstrates that this whole ecosystem has been placed into disequilibrium thereby developing severe land degradation problems as a result of rising saline sulfatic ground watertables and perched watertables due to land-clearing since European settlement. The purpose of this paper is to provide a methodology framework and overall summary for other papers in a series dealing essentially with detailed field and laboratory investigations of individual soil-water processes.
Computing procedures for mapping soil features at sub-catchment scale
Authors: Rinder GE , Fritsch E , Fitzpatrick RW
Published: April 2005

Procedures for detailed mapping of a large number of soil features in small landscape units displayed in either vertical cross section (i.e. soil toposequences) or horizontal plane (i.e. soil maps) are presented. Rom hand coloured drawings that display the soil-landscape features, an Apple Macintosh Computer, with Adobe Illustrator and Adobe Patterns and Textures programs, is used to produce high quality coloured maps ready for reproduction in any form (e.g. posters, publications, slides or overhead transparencies). The first step is to produce the detailed computer map with all soil features included. This detailed computer map is made up of the following three layers or bases: (i) a black linework and lettering base, (ii) a polygon base filled with black and white textures, and (iii) a polygon base filled with colours. The detailed computer map, saved as the master file, is very easily modified to generate more simplified and thematic maps by: (i) grouping soil features into larger soil components in order to display soil-landscapes in a more simplified form, (ii) deleting certain soil-landscape components in order to highlight specific soil features, and (iii) adding newly aquired information (e.g. chemical and hydrological data) to previous versions.
Effect of surface applications of lime, gypsum and phosphogypsum on the alleviating of surface and subsurface acidity in a soil under pasture
Authors: Smith CJ , Peoples MB , Keerthisinghe G , James TR , Garden DL , Tuomi SS
Published: April 2005

Changes in the chemistry of an acidic grey massive earth soil in response to various ameliorant treatments (gypsum and phosphogypsum in the presence or absence of lime) were investigated in a subterranean clover-based pasture in the southern highlands of New South Wales. Lime, gypsum, and phosphogypsum, or lime in combination with gypsum and phosphogypsum were broadcast at 2500 kg ha-1 on the surface of the soil in May 1990. Pasture production was determined and the soil was sampled to 25 cm depth, 6 and 18 months after treatment application. Surface soil pH was increased to 6-1 by the application of lime, gypsum plus lime and phosphogypsum plus lime treatments in the 0-5 cm depth interval, but remained unchanged when gypsum or phosphogypsum was used alone. Calcium chloride extractable aluminium increased down the soil profile under all treatments to 10-15 cm, but was highest in the gypsum treatment at depth. The application of phosphogypsum increased the 0.01 m CaCl2 extractable fluoride in the surface 5 cm from 26 to 43 �M. In contrast, fluoride concentrations were decreased to between 5.3 and 7.3 �M in the lime, gypsum plus lime and phosphogypsum plus lime treatments. Gypsum and phosphogypsum decreased the concentration of Al3+ in solution and on the exchange sites in the 0-5 cm depth interval. However, the effectiveness of the amendments to reduce toxic Al3+ concentrations were confined to the surface 5 cm. The concentration of aluminium and the activity of Al3+ in the 0-5 cm soil layer at both soil samplings were decreased by the amendments. Lime, and gypsum or phosphogypsum in combination with lime, were the most effective treatments for reducing the activity of Al3+. The activity of Al3+ increased with depth in all treatments. The pH and activity of Al3+ measured in the 0.01 m CaCl2 extracts plot near the gibbsite solubility line and suggest that Al solubility was controlled by this mineral. Exchangeable Ca in the 0-5 cm soil layer was significantly increased by the application of lime whereas exchangeable aluminium was decreased by lime, gypsum and phosphogypsum. There was no significant change in exchangeable cations other than Al below the surface 5 cm which suggests limited leaching of lime, gypsum and phosphogypsum in the profile within the 18 month study period. Pasture yield was significantly increased by the addition of lime and was related to the decrease in the activity of Al3+ in the surface soil.
Dissolution rate of phosphate rock particles having a wide range of sizes
Authors: Watkinson JH
Published: April 2005

An equation is proposed that describes the dissolution rate in soil of phosphate rock particles with a wide range of sizes, such as found in fertilizers for direct application. Information needed is the mean dissolution rate constant for the soil, and the dry sieve analysis of the phosphate rock.
Compaction of an earthy sand by rubber tracked and tired vehicles
Authors: Blunden BG , Mcbride RA , Daniel H , Blackwell PS
Published: April 2005

Normal stresses exerted by two agricultural vehicles (a rubber tracked Caterpillar Challenger 65 and a Steiger Tiger 550 4WD tractor fitted with low pressure dual wheels) were measured with electronic earth pressure cells at four depths (150, 300, 400 and 500 mm) in a sandy soil located in the West Australian wheatbelt. Cone penetration resistance and dry bulk density were also measured at these depths before and after traffic treatments. Uniaxial soil compression testing was done on soil cores sampled at the 300 mm depth where the peak normal stresses were measured during vehicle passage. The Cat 65 exerted less normal stress on the soil than the Steiger 550 at 400 and 500 mm depth. However, the soil had a higher penetration resistance after the passage of the Cat 65 relative to the Steiger 550. Profiles of cone penetration resistance were more discriminating in distinguishing soil physical changes among the trafficked and untrafficked treatments than dry bulk density and most of the parameters derived from compression tests.
Effects of fallow management and cropping history on aggregate breakdown under rainfall wetting for a range of Queensland soils
Authors: Loch RJ
Published: April 2005

This paper reports changes in stability of soils to wetting under a range of fallow management/cropping treatments for eight experiment sites in Queensland. Because of its greater relevance to dryland soils, and its better correlation with field soil behaviour, wetting with high energy rain (HER) was used to wet samples and cause aggregate breakdown. The water-stable size fraction considered was that <0.125 mm, with the proportion of particles <0.125 mm referred to as P125. To study interactions between wetting method and tillage management, several other wetting methods were applied to some or all of the eight soils. These other methods were immersion (IMM), wetting by rainfall of low energy (LER) or under tension (TENS). Where fallow management treatments significantly reduced P125 under HER wetting, those reductions were generally small, and likely to increase steady infiltration rates of high energy rain into bare soil by only 2-6 mm h-1. In contrast, steady infiltration rates could be increased by 15-42 mm h-1 if those same soil surfaces were completely covered by stubble so that they received low energy rain. At least under Queensland conditions, retention of crop residues to protect soils from drop impact is therefore likely to be of much greater importance in improving water storage during fallows than any improvement in soil aggregation under 'improved' fallow management practices. Effects of fallow management and cropping history on P125 under HER varied across the sites. Three out of four virgin soils were more stable than corresponding cropped soils; stubble retention improved stability to HER wetting on three out of four sites where it was tested, and direct drill or reductions in tillage frequency improved stability at two out of eight sites. IMM showed responses to treatments that, for some soils, differed greatly from those obtained using HER. Neither LER nor TENS appeared useful, as LER gave occasional inconsistent results, and TENS caused little aggregate breakdown for most soils.
Estimating the pollution potential of pesticides to ground water
Authors: Kookana RS , Aylmore LAG
Published: April 2005

A screening model available in the literature has been used to evaluate the ground water pollution potential of a number of commonly used pesticides under irrigated horticulture in Bassendean sand of the Swan Coastal Plain of Western Australia. The original model assumed a decreasing rate of pesticide degradation but a constant organic matter content with depth in the soil profile. A modified version of the model was developed to take into account the generally decreasing organic matter contents with depth in the soil profile. Residual masses and travel times of 40 pesticides were calculated by the model using sorption and degradation data available from the literature. The calculations based on the constant OM mode predicted that for a recharge rate of 0-5 m/yr, some 14 of the pesticides were likely to reach ground water at appreciable levels of the residue (>0.1% of applied mass). The number increased to 21 and was accompanied by a decrease in the travel times required for the pesticides to reach ground water when the decreasing organic matter contents of the profile with depth were taken into consideration. To assess the validity of using sorption and degradation data from the literature for the local soil, comparisons of model calculations were made for five pesticides whose sorption coefficients and degradation half-lives were measured on the local soil. For some pesticides, the predictions based on literature values were significantly different from those based on measured parameters indicating, as expected, that overseas data may not always represent local conditions. However, they may still provide valuable first approximations of the likely relative pollution potentials of different pesticides.
Adsorption and degradation of triazine herbicides in soils used for lupin production in Western-Australia - Laboratory studies and a simulation model
Authors: Walker SR , Blacklow WM
Published: April 2005

Most lupins (Lupinus angustifolius L. and L. albus L.) grown in Western Australia are sown with simazine, and some with atrazine, to give persistent control of a broad spectrum of weeds. Rates of application are adjusted for soil types yet there can be ineffective weed control and crop damage. The kinetics of degradation in four soils was studied in the laboratory to determine how it varied between soils and was modified by soil temperature, pH, moisture and gamma irradiation. The time for half the herbicide to be lost from the soils (HL) varied from 42 to 110 days at 20�C and -0.08 MPa water potential. Loss was rapid in the first day of incubation and subsequent losses were described precisely by first-order functions. However, the first-order half-lives (t1/2) were 3-21 days greater than the corresponding HLs, because the first-day losses were unaccounted for by the first-order functions. Gamma irradiation had no influence on degradation kinetics which supported chemical hydrolysis as the mechanism of degradation. The t1/2 values were correlated positively with the proportion of applied herbicide that was adsorbed by the soils (PAd). Atrazine was more persistent than simazine and had higher PAd values. The PAd values increased with soil pH, organic matter and clay content. The t1/2 values decreased exponentially with temperatures from 28 to 9-degrees-C, and decreased with soil water potentials from -0.08 to -1.50 MPa for a loamy sand at a near-neutral pH. A computer simulation model gave good agreement with observed residue decays and showed that the initially rapid losses from the soils could be explained by high rates of hydrolysis when all the applied herbicide was in the soil solution and, consequently, herbicide concentrations were high (87-100 mM). Rapid losses of the triazines in the field are likely in warm, acidic soils-particularly if the herbicide concentrations in the soil solution are high for reasons of limited vertical distribution of the applied herbicides through the soil profile.
Corrigenda - Adsorption and degradation of triazine herbicides in soils used for lupin production in Western-Australia - Laboratory studies and a simulation model
Authors: Walker SR , Blacklow WM
Published: April 2005

Most lupins (Lupinus angustifolius L. and L. albus L.) grown in Western Australia are sown with simazine, and some with atrazine, to give persistent control of a broad spectrum of weeds. Rates of application are adjusted for soil types yet there can be ineffective weed control and crop damage. The kinetics of degradation in four soils was studied in the laboratory to determine how it varied between soils and was modified by soil temperature, pH, moisture and gamma irradiation. The time for half the herbicide to be lost from the soils (HL) varied from 42 to 110 days at 20�C and -0.08 MPa water potential. Loss was rapid in the first day of incubation and subsequent losses were described precisely by first-order functions. However, the first-order half-lives (t1/2) were 3-21 days greater than the corresponding HLs, because the first-day losses were unaccounted for by the first-order functions. Gamma irradiation had no influence on degradation kinetics which supported chemical hydrolysis as the mechanism of degradation. The t1/2 values were correlated positively with the proportion of applied herbicide that was adsorbed by the soils (PAd). Atrazine was more persistent than simazine and had higher PAd values. The PAd values increased with soil pH, organic matter and clay content. The t1/2 values decreased exponentially with temperatures from 28 to 9-degrees-C, and decreased with soil water potentials from -0.08 to -1.50 MPa for a loamy sand at a near-neutral pH. A computer simulation model gave good agreement with observed residue decays and showed that the initially rapid losses from the soils could be explained by high rates of hydrolysis when all the applied herbicide was in the soil solution and, consequently, herbicide concentrations were high (87-100 mM). Rapid losses of the triazines in the field are likely in warm, acidic soils-particularly if the herbicide concentrations in the soil solution are high for reasons of limited vertical distribution of the applied herbicides through the soil profile.
Assessment of errors in nutrient analyses of roots
Authors: Misra RK
Published: April 2005

Errors in nutrient analyses of roots may arise from soil adhering to roots, the method of root separation from soil and storage of root samples. Experiments were conducted on fine roots of Eucalyptus nitens from a clay soil to establish a method for estimating true concentrations of nitrogen (N), phosphorus (P) and potassium (K) in root samples (i.e. unbiased by the soil adhering to roots), and to test the adequacy of measurements of ash residues of root samples for estimating the quantity of soil adhering to roots. Results indicated that nutrient concentrations on the basis of ash-free weight of root samples approached true nutrient concentrations of roots when the quality of soil adhering to roots was small, and the nutrient concentration of soil was much lower than the roots. Estimates of true nutrient concentrations of roots calculated from the information on the weight of soil adhering to roots and the nutrient concentration of the soil were satisfactory in the prediction of nutrient content of roots for a range of soil-contamination. The factor which accounted for contamination, and helped estimation of true concentrations from measured concentrations, depended on the magnitude of soil contamination and the relative concentrations of nutrients in roots and soil. Wet separation (washing) of roots from soil compared with dry separation resulted in 24% loss of K. With various methods of storage of washed root samples, the level of soil contamination was 5-20% of the root sample. Submergence of roots in water for 15 days after washing reduced the concentration of N, P and K in roots to 84, 50 and 54% of those roots which were dried immediately following washing. The rate of nutrient loss from roots was greater for K than for N and P when washed samples were stored submerged. On the basis of this study, it is recommended that roots, after separation from soil, should be dried as soon as possible with a minimum exposure of roots to wet conditions. Estimates of soil adhering to roots, and nutrient concentration of the adhering soil, are required to infer correct concentrations of nutrients in root samples.
Land rehabilitation under pasture on volcanic parent materials - Changes in soil microbial biomass and C-metabolism and N-metabolism
Authors: Ross DJ , Mcqueen DJ , Kettles HA
Published: April 2005

Changes in soil biochemical properties during land restoration after mining in a high-rainfall area in the Coromandel Range, North Island, New Zealand, were studied over 3 years in mown, fertilized, grass-legume pastures developed on weathered andesite overburden spread to 60 cm depth over waste rock, and covered with 0 or 15 cm of a silt loam topsoil (a Typic Hapludand). Herbage yields were 53-57% of an adjacent pasture control after 1 year, and 63-69% after 3 years. Total C and N, and microbial C, at 0-7.5 and 7.5-15 cm depths changed little during the trial, but microbial N increased. The fumigation-extraction procedure was routinely employed for estimating microbial biomass C; problems were found with the substrate-induced respiration and fumigation-incubation methods. Ratios of 0.5 M K2SO4-extractable C to total C, and CO2 production to total C or microbial C (qCO2), were highest throughout in the reconstructed soils. Aerobic net N mineralization increased during the trial, but continuing low rates of mineralization and a predominance of N-fixing legumes in the herbage indicated a deficiency of available N in the reconstructed soils. Nitrification occurred readily in all but 7.5-15 cm depth samples of the no-topsoil treatment, where physical conditions were probably adverse. Invertase activity increased appreciably in 0-7.5 cm depth samples of the topsoil treatment, but remained well below control soil values. Overall, the biochemical results are consistent with agronomic data in showing that the use of some topsoil in rehabilitation at a site such as this is desirable.
Changes in microbial biomass and organic matter levels during the first year of modified tillage and stubble management practices on a red earth
Authors: Gupta V , Roper MM , Kirkegaard JA , Angus JF
Published: April 2005

Farming practices involving stubble burning and excessive tillage in Australia have led to losses of organic matter from the soil. Crop residue retention and reduced tillage practices can reverse these trends, but changes in organic matter levels are evident only after a long term. Microbial biomass (MB), the living portion of soil organic matter, responds rapidly to changes in soil and crop management practices. We evaluated changes in microbial biomass and microbial activity in the first year following the modification of stubble management and tillage practices on a red earth near Harden, New South Wales. Following an oat crop harvested late in 1989, seven treatments involving stubble and tillage management were applied in February 1990. Wheat was planted in May 1990. Measurements of total organic carbon (C) and total nitrogen (N) in the top 15 cm of soil indicated no significant changes after 1 year, although there was a significant effect on the distribution of C and N. However, significant changes in MB were observed in the first year. Microbial biomass C in the top 5 cm of the soil ranged from 25 to 52 g C m-2 and these levels dropped by 50% or more with each 5 cm depth. Implementation of treatments altered MB, particularly in the top 5 cm where MB-C and MB-N were significantly greater in stubble-retained than in the top 5 cm where MB-C and MB-N were significantly greater in stubble-retained than in the stubble-burnt treatments, and in the direct drill treatment than in the stubble-incorporated treatment. Microbial biomass in soil increased during the growth of wheat in all treatments, but this was slower in the standing stubble-direct drill treatment, probably due to the delay in the decomposition of stubble. Microbial respiration, which was concentrated in the surface 5 cm of soil in all treatments, was greatest in the direct drill treatments. Microbial activity below 5 cm was higher with stubble incorporation than with direct drill. Specific microbial activity (microbial respiration per unit MB) had the greatest response to tillage at 10-15 cm depth. Microbial quotients (MB as a percentage of C or N) responded to changes in tillage but not significantly to stubble retention. Our studies, during the first year following the modification of stubble management and tillage practices, suggested that changes in MB and microbial activity may be sensitive and reliable indicators of long-term changes in organic matter in soils.
Seasonal activity and estivation of lumbricid earthworms in the midlands of Tasmania
Authors: Garnsey RB
Published: April 2005

Earthworms have the ability to alleviate many soil degradational problems in Australia. An attempt to optimize this resource requires fundamental understanding of earthworm ecology. This study reports the seasonal changes in earthworm populations in the Midlands of Tasmania (<600 mm rainfall p.a.), and examines, for the first time in Australia, the behaviour and survival rates of aestivating earthworms. Earthworms were sampled from 14 permanent pastures in the Midlands from May 1992 to February 1994. Earthworm activity was significantly correlated with soil moisture; maximum earthworm activity in the surface soil was evident during the wetter months of winter and early spring, followed by aestivation in the surface and subsoils during the drier summer months. The two most abundant earthworm species found in the Midlands were Aporrectodea caliginosa (maximum of 174.8 m-2 or 55.06 g m-2) and A. trapezoides (86 m-2 or 52.03 g m-2), with low numbers of Octolasion cyaneum, Lumbricus rubellus and A. rosea. The phenology of A. caliginosa relating to rainfall contrasted with that of A. trapezoides in this study. A caliginosa was particularly dependent upon rainfall in the Midlands: population density, cocoon production and adult development of A. caliginosa were reduced as rainfall reduced from 600 to 425 mm p.a. In contrast, the density and biomass of A. trapezoides were unaffected by rainfall over the same range: cocoon production and adult development continued regardless of rainfall. The depth of earthworm aestivation during the summers of 1992-94 was similar in each year. Most individuals were in aestivation at a depth of 150-200 mm, regardless of species, soil moisture or texture. Smaller aestivating individuals were located nearer the soil surface, as was shown by an increase in mean mass of aestivating individuals with depth. There was a high mortality associated with summer aestivation of up to 60% for juvenile, and 63% for adult earthworms in 1993 in the Midlands. Cocoons did not survive during the summers of 1992 or 1994, but were recovered in 1993, possibly due to the influence of rainfall during late winter and early spring.
Evaluation of the 137Cs techniques for estimating wind erosion losses for some sandy Western Australian soils
Authors: Harper RJ , Gilkes RJ
Published: April 2005

The utility of the caesium-137 (137Cs) technique, for estimating the effects of wind erosion, was evaluated on the soils of a semi-arid agricultural area near Jerramungup, Western Australia. The past incidence of wind erosion was estimated from field observations of soil profile morphology and an existing remote sensing study. Erosion was limited to sandy surfaced soils (0-4% clay), with a highly significant difference (P < 0.0001) in 137Cs values between eroded and non-eroded sandy soils, with mean values of 243 � 17 and 386 � 13 Bq m-2 respectively. Non-eroded soils, with larger clay contents, had a mean 137Cs scontent of 421 � 26 Bq m-2, however, due to considerable variation between replicate samples, this value was not significantly different from that of the non-eroded sands. Hence, although the technique discriminates between eroded and non-eroded areas, the large variation in 137Cs values means that from 27 to 96 replicate samples are required to provide statistically valid estimates of 137Cs loss. The occurrence of around 18% of the total 137Cs between 10 and 20 cm depth in these soils, despite cultivation being confined to the surface 9 cm, suggests that leaching of 137Cs occurs in the sandy soils, although there was no relationship between clay content and 137Cs value for either eroded or non-eroded soils. In a multiple linear regression, organic carbon content and the mean grain size of the eroded soils explained 35% of the variation in 137Cs content. This relationship suggests that both organic carbon and 137Cs are removed by erosion, with erosion being more prevalent on soils with a finer sand fraction. Clay and silt contents do not vary with depth in the near-surface horizons of the eroded sandy soils, hence it is likely that wind erosion strips the entire surface horizon with its 137Cscontent, rather than selectively winnowing fine material.
An in situ mini lysimeter with a removable ion exchange resin trap for measuring nutrient losses by leaching from grazed pastures
Authors: Sakadevan K , Hedley MJ , Mackay AD
Published: April 2005

This study describes the construction, installation and evaluation of an in situ mini-lysimeter with a removable ion exchange resin trap for measuring nutrient losses by leaching from grazed pastures. The resin trap efficiently removed solutes from simulated drainage water at a flow rate of 14 mm h-1. Over 88% of each of the solutes was removed from synthetic nutrient solution containing 1.65 mM nitrate-N, 1.65 mM ammonium-N, 0.25 mM sulfate-S (SO2-4-S) and 0.6 mM potassium. In a further test of the system, sulfate leached in simulated rainstorm events from two undisturbed soil cores, taken from legume based pastures of contrasting superphosphate (SSP) fertilizer history following 495 mm of simulated rainfall, was all recovered using the resin trap. Seven times more SO2-4 (21.2 kg S ha-1) was leached and recovered from the resin trap of the core collected from the high fertility (HF, 375 kg SSP ha-1 year-1) site than from the low fertility (LF, 125 kg SSP ha-1 year-1) site (3.1 kg S ha-1). As part of the field evaluation of the technique, lysimeters with resin traps were placed in the field at four sites (8 lysimeters/site) contrasting in fertilizer history, landslope, and dung and urine return. Two additional lysimeters with drainage collection reservoirs (vessels) and eight soil solution samplers were placed on each site to collect drainage water and soil solution. The amount of SO2-4 present in drainage water was more closely related (1:1, R2 = 0.861) to the amount of SO2-4 collected by the resin traps over a period of 9 months than estimates made using soil solution samplers (1:1, R2 = 0.829). The advantages of the resin trap technique over alternative methods for estimating SO4-S leaching losses from field soils are discussed, as are applications of the technique for studying nutrient losses and cycling in grazed pastures.
Soil sampling bulk-density in the coastal lowlands of South-East Queensland
Authors: Costantini A
Published: April 2005

Bulk density is commonly measured in compaction, cultivation, land evaluation and site classification studies in forestry. Typically, measurements are made using a small-diameter core sampler (an integral open drive sampler) which is manually driven into the soil profile. The study reported in this paper was designed to determine the effects of sampler size on bulk density estimates, and to identify optimal sampling intensities for the coastal lowlands of south-east Queensland. Four sampler sizes were tested (internal diameters of 3.48, 4.83, 5.98 and 9.12 cm, and all approximately 10 cm in length). All sampler sizes provided consistent estimates of bulk density for a range of soil types and conditions. The accuracy of bulk density assessment was not improved by increasing sampler diameter beyond 5.98 cm. The results suggested that the core sampler technique can be used efficiently in a wider range of soil conditions than that recommended in the literature. Comparison of variances estimated for the four sampler sizes indicated no significant differences between either sampler size or site, and no significant 'site by sampler size' interaction. A single pooled estimate of variance was therefore used to recommend sampling intensities for coastal lowland soils. With any of the samplers used in this study, five replications will provide a point estimate of bulk density with a precision of � 0.1 g cm -3; at the 95% probability level.