bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of organic cosolvent on adsorption and desorption of linuron and simazine in soil
Authors: Kookana RS , Gerritse RG , Aylmore LAG
Published: April 2005

The adsorption and desorption of two herbicides, Linuron and Simazine, on a clay soil have been studied in mixtures of methanol and water. Adsorption of the herbicides decreased with increasing methanol content of the solution. An inverse log-linear relationship between the Freundlich adsorption coefficients for the two herbicides and the concentration of methanol was found. Adsorption of the herbicides in the presence of methanol followed the solvophobic theory, which describes the adsorption of hydrophobic organic compounds in soils. Values of the Freundlich adsorption coefficient for aqueous solutions, of the two herbicides extrapolated from adsorption data for the methanol/water mixtures, showed close agreement with those obtained experimentally. Hence, adsorption in aqueous solutions for pesticides of low aqueous solubility can readily be predicted on this basis. Hysteresis, observed after desorption in CaCl2 solution, decreased with increasing methanol contents for both herbicides. The decrease in hysteresis was ascribed to the swelling of the organic matter and the accompanying increased accessibility to solutes. The study showed that the presence of an organic solvent significantly affected not only the adsorption but also the desorption of herbicides in soils.
Characterization of basaltic clay soils (vertisols) from the Oxford land system in central Queensland
Authors: Webb AA , Dowling AJ
Published: April 2005

Morphological, chemical and physical properties of basaltic clay soils (Vertisols-Usterts and Torrerts) from the Oxford Land System in central Queensland are described and compared over their geographical range of occurrence and also their position in the landscape. These soils are derived from undifferentiated basic lavas and interbedded pyroclastics of Tertiary age. Black earths are the dominant soil group. Position on slope had the biggest influence on depth of soil, with crest and mid-upper slope positions having more shallow (<0.9 m) soils than mid-lower and footslope positions. Soils have very high CEC and clay contents throughout the profile, are mildly alkaline at the surface and strongly so at depth, are non-saline and non-sodic (except in some footslope positions), and have an exchange complex dominated by calcium and magnesium. In the surface 0.1 m, extractable P and Zn, and total N and S levels are low and crop responses to fertilizer are probable. In comparison of 26 paired sites, where areas of native pasture and cultivation occur in close proximity, cultivated soils have lower organic C and total N, P, K and S levels than native pasture soils. This reflects a general decline in soil fertility under cultivation, and has implications for soil management and long-term soil stability.
Exchange equilibria of potassium in some red, black and alluvial soils of India .I. Effect of displacing cations
Authors: Dhillon SK , Dhillon KS
Published: April 2005

Exchange equilibria of K+ versus Ca2+, NH4+ and Na+ were studied in seven benchmark soils representing red, black and alluvial soil groups of India. At low K saturation, illitic (alluvial) soils showed higher K selectivity than smectitic (black) and kaolinitic (red) soils. Fine textured smectitic soils maintained high K selectivity even at high K saturation. Potassium was usually preferred to Ca2+ throughout the range of K saturation encountered, except in one kaolinitic and one illitic soil, where cation preference was reversed at higher K saturation. In the K+-NH4+ exchange system, all the soils in general preferred NH4+ to K+. Smectitic soils preferred K+ to Na+, whereas kaolinitic and illitic soils preferred Na+ to K+. With an increase in K saturation, the activity coefficients of adsorbed Ca2+, NH4+ and Na+ always decreased, but that of K+ initially increased and then decreased to unity. The relative escaping tendency of K from the adsorbed to the solution phase was greater in the K+-Ca2+ system followed by the K+-NH4+ and K+-Na+ systems.
Exchange equilibria of potassium in some red, black and alluvial soils of India .II. Effect of temperature on K+-Ca2+ exchange
Authors: Dhillon SK , Dhillon KS
Published: April 2005

Potassium-calcium exchange equilibria in red (kaolinitic), black (smectitic) and alluvial (illitic) soils of India were studied at 25�C, 40�C and 65�C. The different selectivity coefficients increased in all the soils when the temperature was raised from 25�C to 40�C. Out of seven soils, only in three cases did the exchangeable potassium percentage (EPP) increase with rise in temperature from 25�C to 40�C. When the temperature was further raised to 65�C, EPP as well as selectivity coefficients in the different soils decreased to values less than those observed at 25�C. Similar inferences regarding K selectivity were drawn from normalized exchange isotherms. The sequence of variation in selectivity coefficients with increasing K saturation was Kv > KKDO > KN >KG, where the coefficients are those of Vanselow (Kv), Krishnamoorthy, Davis and Overstreet (KKDO), Gaines and Thomas (KN), and Gapon (KG). The sequence of the coefficients was unaffected by increasing the temperature from 25�C to 65�C. Potassium-calcium exchange was more spontaneous at 40�C than at 25�C. It was non-spontaneous at 65�C in all but the smectitic soils.
Subsoil macropore space of a transitional red-brown earth after either deep tillage, gypsum or both .II. Chemical effects and long term changes
Authors: Blackwell PS , Jayawardane NS , Green TW , Wood JT , Blackwell J , Beatty HJ
Published: April 2005

The management of sodic texture-contrast soils of the riverine plains of S.E. Australia for crops other than rice is difficult because improved subsoil structure often deteriorates after a few seasons of irrigated cropping. This research aimed to improve understanding of the processess which cause deterioration of macropore space (volume and permeability of air-filled soil at -10 kPa matric potential) as well as providing some guidelines for improved management. A transitional red-brown earth was ameliorated by eight different treatments and compared with an unameliorated control treatment in a field experiment. The treatments included surface gypsum application, deep ripping after gypsum application, five designs of gypsum-enriched slots and traffic-free beds after addition of gypsum and deep ripping. The macropore space of the subsoil after initial winter cropping and summer fallow is described from measurements on soil cores collected from the experiment. An index of electrochemical stability (EC/ESP) is proposed which explains the loss of macroporosity of cultivated subsoil in the absence of significant soil stressing by wheels. Considerable loss of macropore volume and permeability after the first summer crop could be associated with loss of soluble gypsum, some increases of exchangeable sodium and compression by lateral swelling of the uncultivated soil from between the slots. These changes were compensated by an increase in the number of vertical fissures, directly observed and deduced from measurements of water entry into whole plots. Thus, management of the balance of soluble salts is essential for the long-term productivity and profitability of such systems of amelioration using deep tillage zones and gypsum application. This is in the absence of significant compaction under wheels or opportunities for addition or organic matter and formation of biopores by roots and soil animals. The relief of lateral swelling of the uncultivated B horizon by the loose slots and formation of extra vertical fissures is a process which may provide long-term benefits and deserves further research.
Movement of solutes associated with intermittent soil-water flow .I. Tritium and bromide
Authors: Scotter DR , Tillman RW
Published: April 2005

The movement of tritiated water and bromide through columns of repacked silt loam was examined in the laboratory. A pulse (5 mm) of a dilute solution of potassium bromide in tritiated water was applied, left for 3 or 10 days, and then leached further down the column of soil with 30 mm of distilled water. Twelve days after the solute pulse was applied, the columns were sectioned, and the distributions of water, tritiated water and bromide were measured. The bromide moved only slightly further than the tritiated water, indicating little anion exclusion. The bromide peaks were much sharper than those for tritiated water. This reflects the slower diffusion of bromide during the periods of several days between leaching and the termination of the experiment, and the importance of molecular diffusion relative to hydrodynamic dispersion. Given the soil hydraulic properties, the behaviour of water, tritiated water and bromide could be simulated by coupling the water flow equations with the convection-dispersion equation, and by using solute diffusivity and dispersivity values from the literature. A significant assumption was which cation was mostly convected with, and hence diffused with, the bromide. The use of the diffusion coefficient for calcium bromide rather than potassium bromide resulted in a better description of the observed bromide profiles in the soil.
Clay mineralogy of soils formed in tuffaceous greywacke, Southland, New Zealand, in relation to genesis, soil properties and classification
Authors: Churchman GJ , Mcintosh PD , Burke CM , Whitton JS
Published: April 2005

The clay mineralogy of 12 soils (Dystrochrepts, a Eutrochrept, a Cryochrept and a Placaquept) formed in tuffaceous greywacke parent rocks is presented and discussed. In a New Zealand context, the soils are unusual because of their base-rich parent material which has been partly pre-weathered to smectite and kaolin minerals in geological time. Superimposed on this assemblage are the affects of present climate and soil drainage, which have altered smectite and vermiculite to dioctahedral (aluminous) chlorite. Conventional laboratory treatments cause dioctahedral chlorite to revert fully to smectite or vermiculite, or alternatively partially to interlayered hydrous mica. The labile nature of the interlayer Al is evident in high KCI-Al values. Allophane and gibbsite occur in acid upland soils that are also trace-element deficient. More intense leaching of upland soils with respect to lowland soils accounts for the upland soils' clay mineralogy and trace element deficiencies. The soils fall into three mineralogy classes of Soil Taxonomy and six classes of the proposed Whitton and Childs revision. The classes are not readily usable in the field, and subgroup or family distinctions based on simple chemical tests are suggested.
Evaluation of methods for inferring air and water properties of soils from field morphology
Authors: Mckenzie NJ , Smettem KRJ , Ringrose-Voase AJ
Published: April 2005

The accurate characterization of soil water and air properties is difficult in soil survey because of logistic constraints. Less reliable surrogates are commonly used to estimate these properties. The surrogates provide a method for moving from measures that tend to be static and semi-empirical to those characterizing soil processes. The utility of four schemes for predicting air-filled porosity, available water capacity and saturated hydraulic conductivity on the basis of field-determined soil morphology has been assessed using data from a limited number of profiles with features commonly encountered in Australia. None of the systems provided statistically significant predictions of available water capacity and the results for air-filled porosity were moderate (McKeague et al. (1986), r2 = 0.58; Hall et al. (19771, r2 = 0 -64; Williams et al. (1991), r2 = 0.70). Encouragingly, the Hollis and Woods (1989) system generated good predictions of field-saturated hydraulic conductivity (r2 = 0.77). It is concluded that better measurement methods and programs of data collection are needed for both the properties used as surrogates (e.g. morphology) and those for which predictions are required (e.g. air and water properties).
The relationship of soil properties to the growth of barrel medic at Condobolin, New South-Wales
Authors: Little IP , Chartres CJ , Young RR
Published: April 2005

Poor growth of barrel medic (Medicago truncatula) has been observed in established pasture on the red duplex and gradational soils of the semi-arid sheep and wheat growing areas of western New South Wales. Red-brown earth soils were examined from three paddocks on Condobolin Research and Advisory Station in conjunction with a visual assessment of the growth of medic. The soils were sampled at 20 m intervals along three line transects in each of three paddocks with different cropping histories. Bray-P; pH, Mn and Al extracted by 0.01 M CaCl2; exchangeable plus soluble Na, K, Ca and Mg; and pH in a 1:5 soil/water suspension were measured at four depth increments at each sampling point. Although the pH in CaCl2 was often less than 5.0, in general no Al was extracted from the 0-5 cm soil layer. Classification of the soils on medic growth alone showed medics were absent from the most acid soils. However, there was considerable within class variability. A better approach was provided by classifying the soils by means of a Euclidean distance/flexible sort of scores from the first principal component. This classification showed that the poorest medic growth was associated with the most acid group with considerable amounts of Al soluble in 0.01 M CaCl2 in the 10-20 cm horizon. Medics grew best in soils with moderate pH values between 5 and 6 in CaCl2 where there was no soluble A1 and moderate levels of exchangeable Ca and Na and soluble Mn. Medics appeared also to grow less well in more alkaline soils where there was very little soluble Mn. There were no differences between classes in available P. There were differences between paddocks; the uncultivated paddock being the most acid and the paddock with the longest cropping history having more Bray-P, more exchangeable Na and more exchangeable Ca at 10-20 cm. The uncropped paddock became more acid and the base status was lowered by natural soil processes and its condition probably indicates the status of many such soils in the district.
Relationship between mineral N content and N mineralization rate in disturbed and undisturbed soil samples incubated under field and laboratory conditions
Authors: Sierra J
Published: April 2005

An investigation of in situ N mineralization, using undisturbed soil samples, indicated a negative relationship between the mineral N content [(NO3+NH4)-N] at the beginning of the experiment and the mineral N produced during it. This suggests that a maximum value of mineral N accumulation in intact soil cores could be calculated from the relationship between mineral N content and N mineralization rate. This value would be related to the size of the mineralizable N pool. If this hypothesis is true, the amount of mineralizable N could be estimated from in situ incubations and utilized in the modelling of N mineralization in the field. The aim of this work was to verify this hypothesis. The relationship between the mineral N content and the N mineralization rate was analysed for in situ and laboratory incubations of disturbed and undisturbed soil samples. A negative relationship between the two variables was only obtained for the experiments carried out with undisturbed samples (in the field and laboratory incubations) when the soil moisture content was not limiting for N mineralization. Futhermore, in undisturbed samples, a negative relationship between mineralization rates of consecutive incubation periods was observed, i.e. the soil sample producing relatively more, during a given period, produced relatively less in the following period. This relationship suggests a feedback mechanism operating in N mineralization which would be related to a mineralization-immobilization process in soil microsites. Thus, the N mineralization pattern was more complex than that described by initial hypothesis. The possible consequence of this feedback mechanism on in situ N dynamics is discussed.
The long term effects of rotation, tillage and stubble management on soil mineral nitrogen supply to wheat
Authors: Heenan DP , Chan KY
Published: April 2005

Wheat was grown as a monoculture or in rotation with lupin or subterranean clover in a long-term rotation, stubble and tillage experiment established in 1979, on a red earth (Gn 2 . 12) at Wagga Wagga, N.S.W. The effect of rotation, tillage and stubble management on the supply of soil nitrogen, and amounts leached were studied by in situ sequential soil sampling during the wheat phase of the rotation in years 10 and 11. Of the rotations, grazed subterranean clover-wheat accumulated higher mineral nitrogen levels during the wheat phase than a lupin-wheat rotation, which in turn produced higher levels than wheat-wheat. The mean seasonal total of net soil nitrogen mineralized (0-15 cm) was 239 kg N ha-1 for subterranean clover-wheat, 165 kg N ha-1 for lupin-wheat and 99.5 kg N ha-1 for wheat-wheat. In a lupin-wheat rotation, retention of stubble increased the net amount of nitrogen mineralized in both seasons. Direct drilling also increased net mineralization in 1990 but the results were inconsistent in 1989. Losses from the surface 15 cm were closely related to the amounts mineralized, with the highest recorded in subterranean clover-wheat rotations. Percent recovery of soil mineralized nitrogen by the above-ground wheat crop following lupin ranged from 57% to 83%, with both direct drilling and stubble retention reducing recovery. While total plant uptake of nitrogen in a wheat-wheat rotation was low, percent recovery was high (77%), compared with that in a subterranean clover-wheat rotation (60%).
Argillite soil characteristics influencing sustained pastoral production, east coast, North Island, New Zealand
Authors: Mew G , Lee R
Published: April 2005

Shoulder, mid-, and foot-slope profiles from two representative soil toposequences developed on siliceous mudstone, on steep land under cut-over forest and scrub, were described morphologically and analysed for selected chemical, physical and mineralogical properties, principally to determine the constraints to long-term sustainable pastoral production. The soils are low in both available phosphorus and sulfur, but the chief constraint appears to be high subsoil acidity giving rise to toxic levels of exchangeable Al. This is presumed to restrict root growth and N-fixing ability of the mixed grass/clover pastures, thereby severely limiting production through frequent and prolonged summer droughts. According to the revised N.Z. Soil Classification System, five of the six profiles are Brown Soils, and one shoulder profile is a Recent Soil. Close associations with Pallic Soils were noted in down-profile changes in Ca/Mg ratios and relatively high exchangeable Na levels. Following Soil Taxonomy, five of the profiles were classified as Dystrochrepts and one as a Fragiochrept. These classifications indicate site stability for soil formation under the indigenous vegetation cover. Adjoining steep sites under pasture are prone to erosion, however. Soil analytical results indicate that extensive erosion is not necessarily a prerequisite for problems with pastoral production in the region.
Correction
Authors: Wood IM
Published: April 2005

Measurement of the Total Water Potential of Aqueous-Solutions of Polyethylene-Glycol - a Comparison Between Osmometer, Thermocouple Psychrometer and Equilibrated Soil Cores (Vol 31, Pg 7, 1993)
Organic C and nutrients in surface soils from some primary rainforests, derived grasslands and secondary rainforests on the Atherton Tableland in North East Queensland
Authors: Maggs J , Hewett B
Published: April 2005

Some long term effects of (a) converting rainforest to grassland, and (b) rainforest regeneration on cleared land were investigated by comparing chemical properties of mineral soil (0-10 cm depth) from beneath primary rainforest, derived grassland and old secondary rainforest. Grasslands and secondary rainforest. were on land cleared at least 50 years ago. The study was undertaken on the Atherton Tableland in north east Queensland using soils formed on basalt, granite and metamorphic rocks. Organic C, kjeldahl N and labile N were 15-50% lower (P < 0.05) beneath grassland than primary rainforest for all soils, and were higher beneath secondary rainforest than grassland. Exchangeable Ca varied in a similar way in basaltic soils but did not differ between vegetation types in the other soils. Extractable Al was lower under grassland than either forest type for soils formed on granite and metamorphic rock. Total and organic P concentrations did not differ between primary forest and grassland, but were lowest under secondary rainforest for soils on metamorphic rock.
A Ccomparison of sedigraph and pipette methods for soil particle-size analysis
Authors: Buchan GD , Grewal KS , Claydon JJ , Mcpherson RJ
Published: April 2005

The X-ray attenuation (Sedigraph) method for particle-size analysis is known to consistently estimate a finer size distribution than the pipette method. The objectives of this study were to compare the two methods, and to explore the reasons for their divergence. The methods are compared using two data sets from measurements made independently in two New Zealand laboratories, on two different sets of New Zealand soils, covering a range of textures and parent materials. The Sedigraph method gave systematically greater mass percentages at the four measurement diameters (20, 10, 5 and 2 �m). For one data set, the difference between clay (<2 �m) percentages from the two methods is shown to be positively correlated (R2 = 0.625) with total iron content of the sample, for all but one of the soils. This supports a novel hypothesis that the typically greater concentration of Fe (a strong X-ray absorber) in smaller size fractions is the major factor causing the difference. Regression equations are presented for converting the Sedigraph data to their pipette equivalents.
Modifications to self mulching (Ism) behavior and their implications
Authors: Grant CD , Blackmore AV
Published: April 2005

The relationship between a laboratory-based numerical index of self-mulching, I-sm, and the actual ability af soils to re-aggregate from the puddled state mas assessed and confirmed. Self-mulching behaviour, as reflected in this laboratory index, was modified, both by changing the calcium status of soils, and by the mixing together of soils having a wide range of self-mulching tendencies. The results reveal the potential significance of mineralogy and of fabric in the manifestation of self-mulching behaviour and the potential for inducing this sort of behaviour in poorly structured soils.
Corrigenda - Modifications to self mulching (Ism) behavior and their implications
Authors: Grant CD , Blackmore AV
Published: April 2005

The relationship between a laboratory-based numerical index of self-mulching, I-sm, and the actual ability af soils to re-aggregate from the puddled state mas assessed and confirmed. Self-mulching behaviour, as reflected in this laboratory index, was modified, both by changing the calcium status of soils, and by the mixing together of soils having a wide range of self-mulching tendencies. The results reveal the potential significance of mineralogy and of fabric in the manifestation of self-mulching behaviour and the potential for inducing this sort of behaviour in poorly structured soils.
National conference on sodic soils - Summary and conclusions
Authors: Naidu R , Sumner ME , Rengasamy P
Published: April 2005

Sodic soils cover over 28% of the total land area in Australia. It is clear from the papers delivered at the conference and workshop that sodic soils are beset with serious chemical, physical and nutritional problems. This report summarises these problems based on the discussions during the workshop sessions together with issues raised during group discussion on: (a) distribution, classification and mapping, (b) physical processes, (c) chemical processes, (d) nutrient constraints, (e) biology and organic matter, (f) environmental consequences and (g) management strategies for economically sustainable crop production on sodic soils. The most serious problems raised during the meeting concern inappropriate definition of sodic soils, soil water balance, nutritional requirements on sodic soils, chemical and mineralogical bases of structural instability in relation to amelioration strategies, farming systems to improve organic matter and biological activity, and information transfer. These issues are presented in detail.
Hardsetting in the surface horizons of sandy soils and Its implications for soil classification and management
Authors: Harper RJ , Gilkes RJ
Published: April 2005

Marked variations in hardsetting occur in the sandy surface horizons of duplex deep sandy soils in a semi-arid area of Western Australia. Hardsetting by definition only occurs in dry soils and increases with field texture. Soil strength measured on remoulded samples in the laboratory conformed with field assessments of strength (consistence). Most (79%) of the variation in strength between Ap horizon samples was explained by clay content, with small differences in clay content resulting in large differences in strength. Half of the maximum measured strength in the Ap horizons was achieved at a clay content of only 8%. The A2 horizons were markedly stronger than corresponding Ap horizons, despite similar clay contents, and this difference in strength is related to the larger organic matter content of the Ap horizons. Hardsetting of these sandy soils may be explained in terms of the cementing action provided by clay which forms bridges between particles. Organic material weakens these bridges. Hardsetting may affect the wind erodibility of sandy soils, through differences in surface conditions (i.e. loose v. compact) and by increasing the resistance to abrasion by saltating sand. It is not clear what effect it will have on plant performance. Hardsetting is a continuous, rather than discrete soil attribute, and if it is to be described in the field, and used in soil classification schemes, objectives class limits should be defined, perhaps using dry consistence ratings.
Evaluation of the USDA curve number method for agricultural catchments in the Australian semi-arid tropics
Authors: Dilshad M , Peel LJ
Published: April 2005

The USDA-SCS curve number method (5 day antecedent rainfall version) was evaluated using rainfall and runoff data from four catchments at the Douglas-Daly Research Farm, 250 km S.W. of Darwin. These catchments were rotational cropped with maize and soybeans using either conventional or no-till technology. Optimized curve numbers (CNs) were calculated for each catchment and crop type for the various 5 day antecedent rainfall conditions (ARC) by using a grid-based statistical technique known as the Marquardt-Levenberg method. Significance levels (SL) of 0.05 or less were regarded as significant throughout. The curve number method (CNM) was able to describe significant levels of variation in observed rainfall and runoff data. By using optimized curve numbers, the CNM significantly explained up to 98% of the variation in data. Results showed that crop type and soil conservation bank spacing as individual factors had minor or no effect on optimized CNs, and hence on the ability of the CNM to predict runoff. Cropping technology and ARC, however, had a very strong influence on optimized CNs. Optimized CNs obtained in this study provide best estimates of CNs for use on commercial cropping catchments in the region.
Etridiazole may conserve applied nitrogen and increase yield of irrigated cotton
Authors: Rochester IJ , Gaynor H , Constable GA , Saffigna PG
Published: April 2005

Recovery of applied N is often poor in irrigated cotton production in Australia, due to N loss through biological denitrification in the heavy clay soils. We envisaged that the N loss through denitrification could be reduced by limiting the soil nitrate concentration by applying a nitrification inhibitor with the fertilizer. We applied the nitrification inhibitor etridiazole in three field experiments in two cotton-growing seasons (1991-1993). The nitrification of ammonium-N applied as urea or anhydrous ammonia, the cotton crop N uptake and lint yield were monitored; recovery of 15N-labelled urea applied to microplots was assessed at crop maturity. In the first experiment, urea was applied at rates of 0 and 80 kg N ha-1 with etridiazole (applied as Terrazole EC). The recommended etridiazole rate (300 g ha-1) was compared with nil, half and double that rate. In the fertilized treatments where etridiazole was applied, nitrification of ammonium was retarded for more than 2 months, cotton crop N uptake was increased by 28% at maturity and lint yield increased by 18%, relative to the control. Etridiazole application had little effect on soil N concentrations, crop N uptake or lint yield in the unfertilized treatments. Fertilizer recovery was significantly improved from 35 to 50% with etridiazole application. The second experiment (in the following year) was conducted under commercial conditions. Etridiazole was applied with urea at 86, 119 and 154 kg N ha-1. As in Experiment 1, nitrification was delayed, crop N uptake was enhanced at crop maturity and lint yield was significantly increased by 46 kg ha-1 (3% greater than the control) with etridiazole application. In the third experiment, anhydrous ammonia was applied at rates from 0 to 175 kg N ha-1, with and without etridiazole. Recovery of 15N-labelled urea was not significantly altered by etridiazole application from the relatively high (69%) recovery in the control treatment. Maximum lint yield was 130 kg ha-1 (6.9%) higher in the etridiazole treatments, but required the application of additional N to achieve it. These experiments indicated that etridiazole was cost-effective in increasing lint yield of irrigated cotton and conserved applied N where substantial denitrification loss occurred.
Fate of applied phosphate and sulfate in weathered acid soils under leaching conditions
Authors: Lefroy RDB , Santoso D , Blair GJ
Published: April 2005

The ability of a soil to sorb ionic forms of phosphorus (P) and sulfur (S) is a major determinant of the movement of sulfate and phosphate ions in the profile. Earlier research is equivocal concerning the effect of concurrent applications of phosphate and sulfate on soils. Any interaction could have significant consequences for fertilizer management. An experiment was conducted with two contrasting acid soils in open PVC columns. The soils were a gleyed podzolic (Aquic Haplustalf) (GP) (30 �g P g(-1)) soil adsorbed at a soil solution concentration of 0.2 �g P mL(-1)), 13 �g S g(-1)) soil adsorbed at a soil concentration of 5 �g S mL(-1))), and a red earth (Haplohumult) (RE) (30 �g P g(-1)) soil, 48 �g S g(-1)) soil adsorption). A lime x P x S factorial combination was applied to simulate residual P and a topdressing of 32P- and 35S-labelled fertilizer was made as a recent application. The columns were watered to 125% field capacity, at 3 day intervals, until no labelled S or P appeared in the leachate. There was considerable movement of applied P downward in the column of the low-sorbing GP soil. At the end of nine intermittent leachings, the 32P-labelled P recently applied to the surface had moved to the second soil layer (7.5-15 cm), thereby increasing the Colwell P content of this layer from 16 to between 40 and 50 �g P g(-1)) soil. If the soil had been previously treated with P, the recently applied P was leached to the third (15.0-22.5 cm) and fourth (22.5-30 cm) soil layers. In contrast, applied P moved little in the medium-sorbing RE soil. Lime and S application also had no effect on the distribution of applied P in the coil columns. The amounts of recently applied P fertilizer lost by leaching from the RE were less than 2 �g P column-1) of less than 2% of the native+fertilizer P present in the leachate. The S, applied as Na2SO4, was completely leached out of the GP soil by the nine intermittent leachings irrespective of lime or P treatment. The losses of 35S-labelled S recently applied to the surface (>70%) occurred mostly with the second and the third leachings. In the RE soil, a previous application of S resulted in a loss of 34-57% of the applied S after 13 intermittent leachings. Most of his S was lost during the leaching episodes. The application of 98 mu g S g(-1)) soil as a recent S application to the soil surface resulted in increased losses of about 74-121 �g S g(-1)) soil or 37-60% of the applied S. If the soil had a previous S treatment, the S leached amounted to between 36% and 52% of the total S applied. Liming enhanced leaching losses of applied S, and P application only increased S losses in the limed treatment.
Aggregate size distribution and stability of an oxisol under legume-based and pure grass pastures in the eastern Colombian savannas
Authors: Gijsman AJ , Thomas RJ
Published: April 2005

This study evaluated soil aggregate size distribution and stability of an Oxisol under improved grass-only or grass-legume pastures, established in previously native savanna. Three grass-legume combinations were included at various stocking rates. In all treatments and soil layers, soils were well aggregated, having more than 90% of their weight in macroaggregates (>250 �m). The addition of legumes to pastures did not affect the soil aggregate size distribution, although aggregates showed somewhat more stability against slaking. An increase in stocking rate negatively affected both average aggregate size and aggregate stability. Aggregates showed little or no dispersion of clay particles in any treatment. A positive correlation was found between wet aggregate stability and hot-water extractable carbohydrate concentration, supporting the hypothesis that these carbohydrates equate with plant-derived or microbial polysaccharides which glue soil aggregates together. It is suggested that determination of hot-water extractable carbohydrates may serve as a useful indicator of small differences in aggregate stability, even when these differences are not evident in the stability measurement itself.
Effect of depth and lime or phosphorus-fertilizer applications on the soil solution chemistry of some New Zealand pastoral soils
Authors: Wheeler DM , Edmeades DC
Published: April 2005

Thirteen trails were sampled to investigate the effects of depth, or the surface application of lime and phosphorus (P) fertilizer, on solution composition. Soil solutions were extracted by centrifuge from field moist soils within 24 h of sampling. Solution Ca, Mg, Na and K, Al, Mn and Fe concentrations generally decreased and Al, Mn and Fe concentrations generally increased with depth; although exceptions occurred. The largest decrease occurred in the first 25-50 mm of soil. Higher solution Al concentrations occurred in a band at a depth of between 50 and 100 mm in some soils. Lime generally increased solution pH and solution Ca, Mg and HCO3 concentrations, and reduced solution Al, Fe and Mn concentrations in the topsoils. In one soil (Matapiro silt loam) 2 years after lime was applied, lime increased solution pH down to a depth of 100 mm, Ca and HCO3 down to 75 mm and Mg down to 50 mm. Lime also decreased solution Al and Mn down to 75 mm and Fe down to 50 mm. In one series of trials, lime increased solution Ca concentrations at a depth of 50-100 mm 4 years after application in six out of the eight sites. In the same trial series, the application of P fertilizer increased solution P concentrations at 0-50 mm from a mean of 5 �M in the no-added P plots up to a mean of 56 �M at the highest P rate. The highest solution P concentration recorded was 194 �M. The increase in solution P concentrations for a given application of fertilizer P varied from 0.05 to 1.03 �M P per kg P ha-1 applied. Maximum pasture yield and 90% maximum yield occurred when solution P concentrations were about 28 and 14 �M respectively. Solution P concentrations determined from P adsorption isotherms were not a good indicator of solution P concentrations measured in soil. Solution pH was higher than soil pH (1:2.5 soil:water ratio, 2 h equilibration) with a solution pH of 6.0 corresponding to a soil pH in water of about 5.2.
Free aluminum and aluminum complexation capacity of natural organic-matter in acidic forest soil solutions from Canterbury, New Zealand
Authors: Powell HKJ , Hawke DJ
Published: April 2005

Measurement of soil solution Al complexation capacity (Al-CC) at pH 4 . 7 by using a simple colorimetric flow injection analysis technique is described. Forest soils from four sites (Canterbury, N.Z.) of contrasting rainfall (from 655 mm to about 3000 mm) were examined. Results showed a strong inverse correlation (r2 = 0.992) between pH and log(soil solution Al-CC) in high-organic surface horizons, indicating that high rainfall generates both acidity and Al complexing ligands. Soil Al-CC (�mol Al kg-1 dry soil) was highest (199 �mol kg-1) in the Ca horizon from the wettest site, and lowest (2.2 � mol kg-1) in the B horizon of one of the intermediate rainfall sites. Soil solution Al-CC was proportional (r2 = 0.94) to the organic matter content of all horizons, as estimated by absorbance at 250 nm. The slope of the regression against A250, expressed as fulvic acid equivalent, gave a higher Al-CC (1360 � 210 mmol kg-1) than measured for soil fulvic acid alone (550 mmol kg-1), indicating a contribution from non-absorbing complexants. The pH dependence of log(free [Al]) (slope -0.38 � 0.17) implicates colloidal and/or solid phase organics in the control of soluble Al in organic horizons.
Evaluation of the potential to dispose of sewage-sludge. 1. Soil hydraulic and overland-flow properties of Pinus plantations in Queensland
Authors: Costantini A , Loch RJ , Glanville SF , Orange DN
Published: April 2005

The studies reported in this paper were designed to evaluate the potential for disposal of sewage sludge in commercial Pinus plantations at Beerburrum, 50 km north of Brisbane. Soil descriptions and measurements of hydraulic properties were made in three soils, covering the range of perceived site suitability for sludge application. Disc permeameters and a rainfall simulator were used to characterize surface infiltration properties both with and without sludge, and ponded rings were used to assess permeability of the upper B horizon. Although surface hydraulic conductivities were potentially high, infiltration into dry soil was reduced by water repellence associated with fungal matting at the soil surface and mycelia extending through the Al horizon. Surface runoff could be generated from dry soils by relatively low intensity rainfall events, and the rate and volume of runoff was not increased by broadcast sludge application. Hydraulic conductivities of the upper Bt horizons in the lateritic and yellow podzolic soils were high, suggesting that persistent perched watertable development was unlikely. However, the presence of bleached A2 horizons and gleyed Bt horizons with prominent mottling in these soils were interpreted as evidence of periodic regional ground-water intrusion. By contrast, hydraulic conductivity in the Bt horizon of the soloth was low, suggesting that locally restricted drainage occurs. Likely pathways of water movement were inferred for three representative soil types in the proposed sludge application project. There is potential for both Hortonian runoff when antecedent conditions are dry, and saturated runoff during prolonged wet periods. Potential off-site pollution could therefore occur if either solids or solutes from the sludge are susceptible to transport. In addition, preferential how paths of water infiltration were demonstrated, and the potential for accelerated water and solute movement to ground watertables was inferred. The studies reported in this, and the second, paper in the series were used to appraise the potential for either surface water or ground water pollution from land-based sludge disposal.
Effects of management history and legume green manure on soil microorganisms under ‘organic’ vegetable production
Authors: Robertson FA , Morgan WC
Published: April 2005

Pasture and conventionally cultivated vegetable cropping land were converted to ‘organic’ vegetable cropping, where synthetic fertilisers and pesticides were not used. Compost was applied and 0, 1, or 2 legume green manure crops grown in rotations. Soil bacterial numbers and fungal hyphal length (microscopic observation), microbial biomass carbon (C) and nitrogen (N) (fumigation–incubation): and water content were monitored over 18 months. All variables were initially greater in ex-pasture than in ex-vegetable soils. Bacterial count declined during the first 6 months under both ex-pasture and ex-vegetable, and after 2 months there was no difference between histories. Microbial biomass C and N declined during the first 6 months in ex-pasture soils, but remained larger than in ex-vegetable soils, in which there was little change in microbial biomass C and N with time. Fungal hyphal length showed no decline with time and remained greater under ex-pasture. Soil water content was greater under ex-pasture for the duration of tile experiment. Crop rotation had no effect in ex-pasture soils. In ex-vegetable soils, water content, fungal hyphal length, and microbial C and N were increased by the inclusion of 2 (and sometimes 1) legume phases in the relation, but only after the legume residues had been substantially decomposed. The history and rotation effects were attributed to greater organic matter and water contents.
Effects of sowing cowpea on properties of an irrigated Vertisol and growth and yield of succeeding cotton
Authors: Hulugalle NR , Entwistle P
Published: April 2005

The effects of sowing a break crop of cowpea on soil properties, nutrient uptake, growth, and yield of furrow-irrigated cotton were evaluated in a trial conducted from 1993 to 1995 in a Typic Haplustert (Vertisol) with high subsoil compaction in north-western New South Wales, Australia. The experimental treatments were cowpea (Vigna unguiculata Walp.)-cotton (Gossypium hirsutum L.), continuous cotton, and long-fallow cotton (cotton alternating annually with a bare fallow). Cotton was sown in all plots in 1994 with minimum tillage. Soil was sampled to a depth of 0.6 m in August 1993, May–June 1994, and April 1995. Soil properties evaluated were organic matter fractions, resilience (a measure of the self-mulching ability of the soil), plastic limit, strength (as cone resistance), shrinkage indices derived from shrinkage curves, exchangeable Ca, Mg, K, and Na, pH, nitrate-N, and electrical conductivity. Profile water content and water extraction, nutrient uptake, crop vegetative growth, cotton lint yield, and fibre quality were also quantified. Compared with fallowing, sowing either cotton or cowpea in 1993 decreased pH and aggregate size formed after puddling and drying, and increased soil organic matter and plastic limit. Cropping also increased exchangeable cations in the surface 0.3 m of the soil. Nitrate-N in the 0–0.15 m depth was 23% higher after cowpea than after fallow. Amelioration of soil compaction was quickest in the short-term where continuous cotton was sown, but was also observed with time in plots where cowpea was sown in 1993. In comparison with cowpea-cotton and long-fallow cotton, continuous cotton had the highest nutrient uptake. Growth of cotton sown after either fallow or cotton was greater than that of cotton sown after cowpea, with lint yield being highest in the previously fallowed plots. Lint fibre quality did not differ significantly between treatments. Overall, the benefits of sowing cowpea in terms of improvements in soil properties and crop yields were either small or negligible in comparison with fallowing or sowing cotton.
Adsorption of atrazine, simazine, and glyphosate in soils of the Gnangara Mound, Western Australia
Authors: Gerritse RG , Beltran J , Hernandez F
Published: April 2005

Sandy soils were sampled from second rotation sites of Pinus pinaster Ait. on the Gnangara Mound in Western Australia. Adsorption isotherms were measured for atrazine [6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine], simazine [6-chloro-N,N'-diethyl-1,3,5-triazine-2,4-diamine], and glyphosate [N-phosphonomethyl-aminoaceticacid]. Adsorption isotherms were also measured for degradation products of atrazine: hydroxyatrazine [6-hydroxy-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine] (HA), desethylatrazine [6-chloro-N-isopropyl-1,3,5-triazine-2,4-diamine] (DEA); and of glyphosate: aminomethylphosphonic acid (AMPA). The adsorption of the 2 triazines was proportional to soil organic carbon content and was not affected significantly by other soil parameters. The affinity for soil organic carbon was in the order atrazine = simazine = DEA > HA. Affinity of atrazine for the type of organic matter in the Gnangara Mound soils (expressed as Koc) was significantly greater than is commonly reported for other soils. The adsorption of glyphosate and AMPA increased strongly with iron and aluminium content of soils and decreased with increasing soil organic carbon content. This would indicate that glyphosate and AMPA are mainly adsorbed by clay minerals, while soil organic matter competes for adsorption sites and inhibits adsorption. Contrary to what is usually reported for batch adsorption of pesticides in soils, significant increases in adsorption of the triazines and glyphosate were measured after 1 day of equilibration.
Computation of hydraulic conductivity of porous materials using computer-assisted tomography
Authors: Phogat VK , Aylmore LAG
Published: April 2005

The spatial distribution of porosity and continuity of pore space in glass bead and soil aggregate systems has been characterised by application of computer-assisted tomography to gamma-ray attenuation measurements. It has been demonstrated that a useful empirical relationship between hydraulic conductivity and pore size and continuity for the glass bead system as measured by CAT scanning can be derived.
Ammonia volatilisation from soil irrigated with urban sewage effluent
Authors: Smith CJ , Freney JR , Bond WJ
Published: April 2005

Losses of ammonia (NH3) following sewage effluent irrigation of pasture were measured under different climatic conditions at Wagga Wagga, New South Wales. Ammonia volatilisation was measured by the micrometeorological mass balance technique using 2 different passive samplers, and by an indirect technique based on the measurements of ammoniacal-N (NH4+ + NH3) concentration, pH, and temperature of the soil solution in the 0–3 mm soil layer, and wind speed at 1.2 m above the soil surface. Maximal NH3 emission rates were measured directly following the effluent-irrigation. There was reasonable agreement between the 2 different passive gas samplers used to measure NH3 volatilisation. The NH3 volatilised was well related to the product of wind speed and the equilibrium ammonia concentration (calculated from the soil solution measurements) as was found in other studies. In addition, NH3 flux density was strongly related to evaporation; that is, when the water (effluent) evaporated NH3 was lost to the atmosphere. Under high evaporative conditions, a maximum of 24% of the ammoniacal-N in the effluent was lost by volatilisation within 2 days of application.