bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of anhydrous ammonia or urea during the fallow period for winter cereals on the Darling Downs, Queensland .I. Effect of time on soil mineral N at sowing
Authors: Strong WM , Cooper JE
Published: April 2005

Nine field experiments were conducted in 1978, 1981 and 1982 to evaluate applications of anhydrous ammonia (AA) or urea applied during the fallow period (January-May) for winter cereal crops. Following fertilizer application, soil was sampled using a stratified soil coring procedure to determine the rate of transformation of applied N to nitrate (nitrification), the quantity of N remaining in mineral forms (NH4+NO3 and NO2), and the movement of applied N into the subsoil. Nitrification of applied N was usually quite rapid in moist soil, particularly with early application (January, February or March when mean soil temperature was >20�C. Very similar rates of nitrification (0.6-4.7 kg N ha-1 day-1) were found for AA and urea applications in May 1982. Extreme drying of soil following N application reduced nitrification to a very low rate in May 1982 (0.6 kg N ha-1 day-1) and to an undetectable level in January 1981. In moist soil in February 1978, AA applied at 56 kg N ha-1 was nitrified completely after 11 days and the 112 kg N ha-1 rate was estimated to have nitrified completely in about 12 days. Also, AA applied to moist soil in May 1978 was estimated to have nitrified completely in about 28 and 42 days for 56 and 112 kg N ha-1 rates, respectively. Low recovery of early applied N as soil mineral N in June 1981 was associated with very heavy rain received during the latter part of the fallow period (March-May). Soil erosion on sloping sites and on a level site was a likely cause for the very low recovery (<47% that of a May application) of January-applied N, and some movement of mineral N below 0.2 m was also evident. Low recovery in fertilized soil (0.2 m) at the level sites was due to a large proportion of mineral N moving into the subsoil (below 0.9 m at one site). Also, prolonged periods of waterlogging during April probably promoted some loss of N due to denitrification, thus resulting in reduction in soil mineral N levels. Low recoveries of early applied N in mineral forms at the end of relatively drier fallows in 1978 and 1982 were also associated with soil saturating rainfall during the latter part of the fallow period. Where wheat crops responded to applied N, January or February applications were less effective than May applications to increase yield and N content of grain.
Application of anhydrous ammonia or urea during the fallow period for winter cereals on the Darling Downs, Queensland .II. The recovery of 15N by wheat and sorghum in soil and plant at harvest
Authors: Strong WM , Saffigna PG , Cooper JE , Cogle AL
Published: April 2005

Three field experiments were conducted on the Darling Downs (Queensland) to evaluate fertilizer management practices such as application depth and addition of nitrification inhibitor (N-serve), for nitrogen (N) applied in the February-May fallow period for winter cereals. Anhydrous ammonia or urea was applied in February, March or May at two depths (7 or 17 cm), with or without N-serve. Soil fertilized in February generally had a lower mineral-N content at sowing than soil fertilized in May. Deeper application (17 cm) in February did not increase soil mineral-N content to 0.2 m depth in May but addition of N-serve did at one site where it appeared to slow the movement of mineral N into the subsoil (0.2-0.4 m). A companion experiment was conducted at each site in which 15N-enriched urea was applied to a small (1 m2) area at the centre of a 4 m2 fertilized plot. Effects of fertilizer placement and N-serve treatment, as were used in field experiments, were evaluated in terms of crop recovery of 15N and total 15N recovery in plant and soil at harvest. Recovery of 15N by wheat, sown at two sites in June, showed that neither fertilizer management practice, application depth nor N-serve affected 15N recovery. At only one site did wheat recover less February-applied N than May-applied N. N-serve had no effect on 15N recovery by sorghum sown in October, of N applied in February or May, but 15N recovery was increased by deeper fertilizer placement. Total recovery of 15N in soil and plant after wheat harvest was lower (-74%) for February-application than for May-application (>94%). Similarly, total 15N recovery after sorghum was lower the earlier the fertilizer was applied. Unrecovered 15N was presumed lost due to denitrification during periods of temporary waterlogging of surface soil. Use of N-serve with the fertilizer application had no effect in conserving 15N applied for wheat or sorghum. However, deeper (17 cm) placement of N than normal (7 cm) promoted higher total recoveries, and therefore reduced losses, of applied 15N at the three sites.
Preferential nitrate immobilization in alkaline soils
Authors: Rochester IJ , Constable GA , Macleod DA
Published: April 2005

The literature pertaining to N immobilization indicates that ammonium is immobilized in preference to nitrate. Our previous research in an alkaline clay soil has indicated substantial immobilization of nitrate. To verify the preference for immobilization of nitrate or ammonium by the microbial biomass in this and other soil types, the immobilization of ammonium and nitrate from applications of ammonium sulfate and potassium nitrate following the addition of cotton crop stubble was monitored in six soils. The preference for ammonium or nitrate immobilization was highly correlated with each soil's pH, C/N ratio and its nitrification capacity. Nitrate was immobilized in preference to ammonium in neutral and alkaline soils; ammonium was preferentially immobilized in acid soils. No assimilation of nitrate (or nitrification) occurred in the most acid soil. Similarly, little assimilation of ammonium occurred in the most alkaline soil. Two physiological pathways, the nitrate assimilation pathway and the ammonium assimilation pathway, appear to operate concurrently; the dominance of one pathway over the other is indicated by soil pH. The addition of a nitrification inhibitor to an alkaline soil enhanced the immobilization of ammonium. Recovery of 15N confirmed that N was not denitrified, but was biologically immobilized. The immobilization of 1 5 ~ and the apparent immobilization of N were similar in magnitude. The identification of preferential nitrate immobilization has profound biological significance for the cycling of N in alkaline soils.
Impact of soil erosion on production in cropping systems .II. Simulation of production and erosion risks for a wheat cropping system
Authors: Littleboy M , Freebairn DM , Hammer GL , Silburn DM
Published: April 2005

Maintenance of productive soil base by minimizing soil erosion is vital to long-term crop production. In this study, a modelling approach is used to estimate effects of soil erosion on productivity for a wheat cropping system at three locations in northeast Australia, Emerald, Dalby and Gunnedah. Predictions of erosion, runoff and yield decline due to erosion for variations in initial soil depth, slope and fallow management strategy are presented. Rates of yield decline were highest at Emerald due to summer dominance of rainfall resulting in higher runoff during summer fallow periods. On average, soil depth decreased by 0.35 cm year-1 at Emerald, 0.25 cm year-1 at Dalby and 0.1 cm year-1 at Gunnedah for a 5.0% slope, 100 cm initial soil depth and a disc/chisel fallow management strategy. Rates of soil removal and subsequent yield decline were higher for shallower soils, steeper slopes and if management practices provided less stubble cover during the fallow. The productivity half-life concept shows that the productive life of the soil was less than 100 years for some soil depth, climate, slope and management combinations. For other combinations, significant yield decline was predicted after 100 years of cropping. The quantification of erosion-productivity relationships allows us to identify regions of higher risk, to estimate the utility of management options, and provide a basis for focusing research and development of management strategies to preserve long-term production.
Runoff, soil loss and soil physical property changes of light textured surface soils from long term tillage treatments
Authors: Packer IJ , Hamilton GJ , Koen TB
Published: April 2005

A long-term tillage trial was conducted (1981 to 1987) on loamy textured soils to quantify changes in runoff, soil loss and some soil physical properties due to conservation tillage practices. Two sites were established, one at Cowra on a sandy loam textured soil, and the other at Grenfell on a loamy textured soil. The tillage treatments imposed were direct drilling (DD), reduced tillage (RT) and traditional tillage (TT), with grazing at both sites, and a direct drilling ungrazed (NT) treatment at Cowra only. Runoff and soil loss were measured using a rainfall simulator, and sorptivity (S), saturated hydraulic conductivity (Ksat), bulk density to 40 mm (BD4) and 100 mm (BD10), organic carbon (OC) and water stable aggregates (WSA) were measured annually. Runoff decreased significantly in the minimum soil disturbance treatments (NT and DD) at Cowra. Runoff did not decrease in the stubble incorporation treatments despite a significant increase in OC and WSA. Decreases in runoff were due to the development and maintenance of porosity, particularly macropores. Changes in other soil physical properties were generally not significant owing to temporal variability. The regression relationship between OC and WSA, although significant, had little practical value because of high prediction error. Although improvements in soil physical properties were measured, a period of at least five years of cropping at both sites was required before they became significant and consistent.
Soil classification in New Zealand - Legacy and lessons
Authors: Hewitt AE
Published: April 2005

A brief review of the history of soil classification in New Zealand is made in order to place the most recent work in its historical context. The first comprehensive system was inspired by the Russian concepts of zonality, and was published as the New Zealand Genetic Soil Classification by Taylor in 1948. It may be regarded as a grand soil-landscape model that related soil classes to environmental factors. Although successful in stimulating the reconnaissance survey of New Zealand soils, it failed to support the requirements of more intensive land use. Soil Taxonomy was tested as an alternative modem system for a period of 5 years but was found to make inadequate provision for important classes of New Zealand soils. The New Zealand Soil Classification was developed using many of the features of Soil Taxonomy while preserving successful parts of the New Zealand Genetic Soil Classification. Historical lessons include the increasing importance of electronic databases and regional correlation, the importance of nomenclature, the necessity of a national system and the divorce of soil classification from soil-landscape modelling.
Soil organisms and sustainable productivity
Authors: Lee KE , Pankhurst CE
Published: April 2005

The soil is a habitat for a vast, complex and interactive community of soil organisms whose activities largely determine the chemical and physical properties of the soil. In a fertile soil the soil biota may have a biomass exceeding 20 t ha-1, with life forms ranging from microscopic bacteria to the largest of earthworms which may be 1 m in length. Only a small fraction, probably <20%, of the soil microflora and microfauna (including bacteria, fungi, algae, protozoa, nematodes, collembola, acari) have been described. The role of soil organisms in the development and maintenance of soil structure, in nutrient cycling and in their various interactions (including associative, harmful and beneficial) with plant roots is described. Trophic interactions between soil organism groups in developed agroecosystems are considered in relation to nutrient cycling and the impact such interactions have on populations of saprophytic, parasitic and symbiotic microorganisms. Prospects for the management of the soil biota to promote sustainable productivity are illustrated by describing the effects of tillage on the composition of soil organism communities. Management technologies that conserve the biodiversity of communities may provide the greatest benefits for the long term sustainability of the soil resource.
Development and application of modern soil erosion prediction technology - The USDA experience
Authors: Lane LJ , Renard KG , Foster GR , Laflen JM
Published: April 2005

Erosion prediction efforts are described to provide a synopsis of the USDA's experience in developing and applying soil erosion prediction technology in its research and development activities and its soil conservation programs. For almost five decades, equations to predict soil erosion by water have been useful m developing plans for controlling soil erosion and sedimentation. The Universal Soil Low Equation (USLE) is the most widely known and used of the erosion prediction equations. The USLE presents a simply understood and easily applied technology which has been of incalculable benefit to soil conservation and land management. The Chemicals, Runoff, and Erosion from Agricultural Management Systems Model (CREAMS) contains a sophisticated erosion component based, in part, on the USLE and on flow hydraulics and the processes of sediment detachment, transport, and deposition. In 1985, the USDA in cooperation with BLM and several universities initiated a national project called the Water Erosion Prediction Project (WEPP) to develop a next generation water erosion prediction technology. The Revised Universal Soil Loss Equation (RUSLE) is an update of the USLE to improve erosion prediction in the interim before WEPP is adopted and to provide and adjunct technology thereafter.
On variation, uncertainty and informatics in environmental soil management
Authors: Mcbratney AB
Published: April 2005

The soil scientist's duty in the debate on environmental management is, at least, to understand the soil and to provide and purvey accurate and precise information concerning it. This paper deals with information m environmental soil management; especially the way its quality and quantity may be modified by soil variation and various kinds of uncertainty, and how its presentation may be enhanced by the accoutrements of information technology. Soil exhibits continuous change m space and time. This variation is usually considered to be problematic in relation to sampling effort, quality of information and for optimal soil management. When ecological principles are considered soil variation is seen as a risk-averse strategy and may be advantageous for sustainable management. Evidence from cultivation is presented to support this hypothesis. The concept of pedodiversity is discussed and a simple example of an optimal preservation strategy based on pedodiversity is given. Three types of uncertainty in soil information are considered in detail: stochastic, deterministic and semantic. The tools of informatics which allow the soil scientist to provide more information or more detailed information for the same effort are discussed briefly These are knowledge-based systems, simulation modelling, spatial and temporal statistics and geostatistics, multivariate techniques, aspatial and spatial information systems. Combinations of these techniques are particularly powerful. Environmental soil management requires a philosophy that generates ways of thinking about soil from which flows realistic soil data models. Such models can be manipulated by the tools of informatics which are not to be considered as ends in themselves.
Effect of soil loosening on the hydraulic properties of a duplex soil
Authors: Jayawardane NS , Prathapar SA
Published: April 2005

In a duplex, transitional red-brown earth, the relationships between hydraulic conductivity K, diffusivity D, soil water potential (�) and volumetric water content (�) in different soil layers were evaluated. Changes in these relationships and in the derived parameters; macroscopic capillary length and characteristic microscopic pore radius due to soil loosening were examined. Replicated large undisturbed and repacked cores of 0.75 m diameter and 1.35 m deep, located in a lysimeter, were used in this study. The K- � relationships were measured during steady upward flow from a watertable at different depths. The � � relationships were measured during a soil drying cycle. The undisturbed soil showed similar soil water characteristics (�-� curves) in all soil layers, at depths greater than 0.25 m. In contrast, K at high � was significantly lower in the upper subsoil, 'throttle' layer with high clay content, compared with the deeper soil layers. However, previous studies on a similar soil have also shown that factors other than pore size distribution, such as tortuosity and pore connectivity, markedly influence the hydraulic conductivity properties of clay soils. Coefficients in the log � on log� and in the log K(�) on log � relationships for all soil layers combined differed markedly from the coefficients for individual layers, indicating the need to measure these properties separately for different subsoil clay layers of this duplex soil. The repacking of the soil to a lower bulk density caused an increase in K at high � values. This was accompanied by a significant decrease in slope of the log � -log � relationship, from 17-21 to around 7, in the subsoil layers. The slope of the regression of log � - K(�) on log� changed from 24 in undisturbed soil to 9 in the repacked soil. This was mainly due to large changes in the � -�relationship, in combination with smaller changes in the K- � relationship. The decrease in diffusivity D with reduction in 0 was less marked in the repacked soil compared with the undisturbed soil. Thus, soil repacking shifted D(�) towards a constant value, for the range of � measured. This was mainly due to a slower rate of change in K with decrease in � on the repacked soil, combined with a compensating increase in d � /d� values. The calculated values of macroscopic capillary length decreased and characteristic pore radius increased, reflecting the changes in pore sizes and hydraulic conductivities due to soil loosening. However, at any given supply and antecedent �, the sorptivity was greater in the loosened soil due to larger changes in water content and hydraulic conductivities. The potential application of these soil properties in evaluating water flow in undisturbed or loosened soils is briefly discussed.
Soil acidification in urine affected and urea affected soil
Authors: Black AS
Published: April 2005

Return of sheep urine (2.2 g N L-1) and urea solutions (0, 6, 9 and 12 g N L-1) to a red podzolic soil in pot experiments resulted in acidification following nitrification. The pH decrease in 0 to 10 cm soil ranged from 0.2 to 0.8 units with the decrease being linearly related (r2 = 0.96, P < 0.01) to the NO3- produced which generally increased with N return. Acid subsurface layers developed in all urine/urea treatments within 6 to 10 weeks following urea-N return. During subsequent plant growth, between 0 and 78% of acid released from urine/urea solution treatments was neutralized. Neutralization was greatest at low rates of N return and when NO-3 was not removed from the soil by leaching before plant uptake. The trend in the relationship between N uptake by plants and acid neutralization was not significant. As a result of plant growth in control pots, the surface soil pH decreased, while in the subsurface layers the pH increased. Based on the extent of acidification observed here, urinary return to grazed pastures could lead to a pH decrease in the surface 10 cm of soil of up to 0.5 units over a 10 year period.
Correction
Authors: Greene RSB , Sawtell GR
Published: April 2005

A Collection System for Measuring Runoff and Soil-Erosion With a Mobile Rainfall Simulator on Sealed and Stony Red Earth Soils (Australian Journal of Soil Research, Vol 30, Pg458, 1992)
Measurement of the total water potential of aqueous solutions of polyethylene glycol - A comparison between osmometer, thermocouple psychrometer and equilibrated soil cores
Authors: Wood IM , Dart IK , So HB
Published: April 2005

This study examined two polyethylene glycol (PEG) polymers (PEG 6000 and PEG 10000) and compared measurements of water potential obtained with a thermocouple osmometer and thermocouple psychrometers at three temperatures (15, 25 and 35�C) and five osmdalities (50, 100, 200, 300 and 400 g/1000 g water). These were then compared with estimates of matric potential of three soils brought to equilibrium with PEG solutions of the same osmolalities. At the same osmolality and temperature the two PEG polymers gave essentially the same water potential. There was a significant effect of temperature on water potential which corresponded closely with changes in specific gravity of the PEG solution. There was a close correlation between the measurements of water potential of the PEG solutions obtained with the osmometer and the psychrometers (R = 0.99). However, the psychrometer gave increasingly lower values than the osmometer as water potential decreased. The differences in the measurements between the two methods are thought to be the result of design and calibration differences. The ease of use of the osmometer is such that it is recommended for routine use. The water potentials of the soil cores brought to equilibrium with the PEG 10 000 solution were linearly related to the water potentials of the PEG solutions estimated from both the osmometer and psychrometers (R2 = 0.84). However, there were clear deviations from a 1:l relationship. It was concluded that the results from the soil cores could not be used to determine which of the two instruments gave the more accurate measurement of water potential of PEG solutions.
Corrigenda - Measurement of the total water potential of aqueous solutions of polyethylene glycol - A comparison between osmometer, thermocouple psychrometer and equilibrated soil cores
Authors: Wood IM , Dart IK , So HB
Published: April 2005

This study examined two polyethylene glycol (PEG) polymers (PEG 6000 and PEG 10000) and compared measurements of water potential obtained with a thermocouple osmometer and thermocouple psychrometers at three temperatures (15, 25 and 35�C) and five osmdalities (50, 100, 200, 300 and 400 g/1000 g water). These were then compared with estimates of matric potential of three soils brought to equilibrium with PEG solutions of the same osmolalities. At the same osmolality and temperature the two PEG polymers gave essentially the same water potential. There was a significant effect of temperature on water potential which corresponded closely with changes in specific gravity of the PEG solution. There was a close correlation between the measurements of water potential of the PEG solutions obtained with the osmometer and the psychrometers (R = 0.99). However, the psychrometer gave increasingly lower values than the osmometer as water potential decreased. The differences in the measurements between the two methods are thought to be the result of design and calibration differences. The ease of use of the osmometer is such that it is recommended for routine use. The water potentials of the soil cores brought to equilibrium with the PEG 10 000 solution were linearly related to the water potentials of the PEG solutions estimated from both the osmometer and psychrometers (R2 = 0.84). However, there were clear deviations from a 1:l relationship. It was concluded that the results from the soil cores could not be used to determine which of the two instruments gave the more accurate measurement of water potential of PEG solutions.
Surface hydraulic properties of a red earth under continuous cropping with different management practices
Authors: Chan KY , Heenan DP
Published: April 2005

Differences in surface soil hydraulic properties after 10 years of different tillage (direct drilled (DD) versus conventional tillage (CT)) and stubble management practices (stubble retained (SR) versus stubble burnt (SB)) were measured in a lupin/wheat rotation on a red earth at Wagga Wagga, NSW. Sorptivity and hydraulic conductivity measurements using a disk permeameter under negative matric potential (-40 mrn) was complicated by water repellence found under SR as compared to SB treatments. Using water, K-40 of SR/DD was only 40% of SB/CT. However, using a wetting agent instead of water increased K-40 of SR/DD by >400% but did not significantly change that of SB/CT such that K-40 was similar for the two treatments. Despite similar bulk density, hydraulic conductivity under ponded infiltration of SR/DD was 4.1 times that of SB/CT. Differences in hydraulic conductivity between -40 mm and under ponded conditions suggest the presence of significantly more transmitting macropores >1.5 mm in diameter under direct drilling. Dye infiltration results indicated that tillage significantly reduced the number of transmitting macropores (>1 mm) even though the total number of macropores remained similar amongst the different treatments. 65% of the macropores were transmitting under SR/DD compared to 1% under SB/CT. A significant correlation (r2=0.82**) was found between transmitting pores (>1.0 mm) and the earthworm population. Tillage but not stubble burning significantly reduced earthworm population.
The long term fate of copper fertilizer applied to a lateritic sandy soil in Western Australia
Authors: Mclaren RG , Ritchie GSP
Published: April 2005

A soil copper fractionation was carried out on soils sampled from plots in a long-term copper fertilizer trial on a lateritic sandy soil in Western Australia. At copper application rates up to 8.25 kg copper sulphate ha-1, a high proportion of the applied copper was initially associated with the soil organic matter. During the course of the trial (20 years), a substantial proportion of this copper became redistributed to a residual soil fraction, i.e. the residue remaining after extractions to remove organic matter and iron oxides. However, significant redistribution of copper with time was not detected in plots with a higher rate of copper application (19.25 kg copper sulphate ha-1). The change in distribution of copper at the lower copper application rates appeared to be only partly responsible for a corresponding decrease observed in EDTA-extractable soil copper during the trial. The changes with time in the nature of fertilizer copper applied to this soil are considered to be responsible for the previously observed decline in plant availability of such copper.
Oxidation rate of elemental sulfur particles with a wide range of sizes
Authors: Watkinson JH
Published: April 2005

An equation is proposed that describes the oxidation rate of elemental sulfur particles with a wide range of sizes, such as would be found in fertilizers. The only information needed is the mean oxidation rate constant over the period of interest and, from a sieve analysis, the proportions of the total mass in each sieve fraction (ratio of upper to lower size < to 2).
Corrigenda - Oxidation rate of elemental sulfur particles with a wide range of sizes
Authors: Watkinson JH
Published: April 2005

An equation is proposed that describes the oxidation rate of elemental sulfur particles with a wide range of sizes, such as would be found in fertilizers. The only information needed is the mean oxidation rate constant over the period of interest and, from a sieve analysis, the proportions of the total mass in each sieve fraction (ratio of upper to lower size < to 2).
Estimating the electrical conductivity of saturated paste extracts from 1:5 soil, water suspensions and texture
Authors: Slavich PG , Petterson GH
Published: April 2005

This paper presents a method of estimating the electrical conductivity (EC) of a saturated paste extract (ECe) from the EC of a 1 to 5 soil/water suspension (EC1:5) and an estimate of soil texture. The method has application in soil testing laboratories which routinely determine EC1:5 but not ECe. The method of preparing the saturated paste by capillary wetting is also compared with the standard method of hand mixing. The coefficient (f) relating ECe to EC1:5, i.e. ECe = fEC1:5 was found to be related to the water content of the saturated paste (�SP kg/kg) by f = 2.46 + 3.03/QSP. The relationship between �SP and texture, determined by hand working, indicates that the uncertainty associated with use of this relationship could be significant in sandy soils. Wetting the soil by capillarity rather than by hand mixing resulted in a lower saturation percentage and higher ECe but dissolved the same amount of salts. The capillary wetting method is preferred as it greatly reduces labour time.
Defining soil macrofauna composition and activity for biopedological studies - A case study on two soils in the Western Australian wheat belt
Authors: Debruyn LAL
Published: April 2005

In Durokoppin reserve and surrounding farmland, part of the central wheatbelt region, pitfall trapping and mapping of soil macrofauna activity were used to define the extent of soil macrofauna activity in these two environments. This type of study is a necessary precursor to determining the significance of certain invertebrate activity in soil modification in these habitats. The relative merits of the two techniques in determining the extent of soil macrofauna activity is assessed. The soil macrofauna groups identified by mapping and pitfall trapping as making a substantial contribution (in terms of relative abundance and activity) in all habitats were, in descending order, ants, spiders and scorpions (wandoo woodland only). In general there was good agreement between the two techniques in identifying the major species and trends in species composition between habitats, but mapping failed to identify the rare or cryptic species. Mapping more accurately identified the resident species in each habitat compared with pitfall trapping. Pitfall trapping data indicated that foraging activity of most soil macrofauna was depressed over winter, except for beetles, and was higher in the spring and summer sampling periods. However, mapping revealed a more constant level of soil macrofauna activity, especially for ant nests. It is argued that the two approaches complement one another and that each has value in interpreting the effects of soil macrofauna activity on soil properties in further studies. The discussion is based on the results of a study carried out in the Kellerberrin area of Western Australia.
Retention and release of diquat and paraquat herbicides in soils
Authors: Kookana RS , Aylmore LAG
Published: April 2005

The sorption and desorption behaviour of diquat and paraquat, in the presence of different salt concentrations, has been studied in some Western Australian soils varying in physical and chemical properties. Sorption isotherms were found to be of the 'L' type according to the Giles classification with the data fitting well to the Langmuir equation. The sorption capacities of soils for diquat ranged from very high in clay soil (146 400 �mol kg-1) to very low in sand (1765 �mol kg-1) and followed the order of clay content in the soils. The clay soil also showed the highest value for the Langmuir coefficient representing bonding energy. The sorption capacities for the herbicides were less than the CEC of the soils. Both the type and content of clay minerals present in soil were important for sorption and subsequent desorption of the dipyridylium herbicides. An increase in the salt concentration of the soil solution (from 0.005 to 0.05 M CaCl2) resulted in decreases in sorption capacities for the herbicides ranging from some 17% to 40% in the different soils. Both Ca2+ and Na+ cations competed for the sorption sites with the herbicides, but Na+ was not as effective as Ca2+. Desorption of the herbicides was also significantly affected by the salt concentrations of the extractant. After five successive extractions with 0.005 m CaCl2, the total amounts of equilibrium sorption desorbed from the Bassendean surface soil were 13% and 7% for diquat and paraquat, respectively. The percentages of diquat removed by extractions decreased with increasing clay contents in the soils studied. Desorption of diquat was higher than that of paraquat at all salt concentrations. Hysteresis was evident between sorption and desorption isotherms.. As sorption increased, the desorption became easier, indicating that the herbicides were less strongly held. Sorption which occurred in the presence of higher ionic strength solutions of inorganic cations was relatively less susceptible to desorption.
Measurement and estimation of capillary upflow from water tables under maize on irrigated soils
Authors: Prathapar SA , Meyer WS
Published: April 2005

An experiment with maize on two soils in lysimeters L1 and L2 (Hanwood clay loam and Mundiwa clay loam respectively) was conducted to measure daily capillary upflow and to establish a relationship between capillary upflow and significant soil, watertable, crop and environmental factors. Total evapotranspiration from L1 and L2 during the season was 748 and 631 mm respectively. Capillary upflow contribution to evapotranspiration in L1 and L2 was 215 (29%) and 101 (16%) mm respectively. Daily capillary upflow ranged from 0 to 5 mm day-1 in the Hanwood clay loam and 0 to 2 mm day-1 in the Mundiwa clay loam during the experiment. Measured daily capillary upflow was significantly (P < 0.001) different between the two soils studied. A stepwise multiple regression, by using the combined data from L1 and L2, showed that the depth to the watertable, water content of the soil layers at 0.1 and 0.4 m and root length density Lv at 0.65 m significantly influenced capillary upflow (n = 68, R2 = 0.79, P < 0.05) in both soils.
Evaporation through a soil mulch in relation to mulch characteristics and evaporativity
Authors: Jalota SK
Published: April 2005

A simple equation describing the effects of atmospheric parameters and soil mulch characteristics upon vapour flux density through a dry soil mulch was successfully developed. Determination of vapour flux density was made from columns of diameter 0.1 m and length 0.95 m. These were filled with silt loam and sandy loam soils with surfactant-treated soil mulch on the surface which varied in thickness and porosity. The experiments were conducted under different atmospheric evaporativities (E0), which comprised a number of combinations of wind speed and ambient temperature. The observed vapour flux density and that computed with Hanks' equation matched well. The results indicated that evaporation under a given E0 was affected more by temperature than wind speed. However, vapour flux density showed a strong interaction with wind speed, temperature and the soil mulch characteristics such as porosity and thickness.
Influence of sheep rxcreta on pasture uptake and leaching losses of sulfur, nitrogen and potassium from grazed pastures
Authors: Sakadevan K , Mackay AD , Hedley MJ
Published: April 2005

In situ mini-lysimeters with ion exchange resin traps were used to measure the effect of dung and urine return on pasture growth and pasture uptake and leaching losses of sulfur (S), nitrogen (N) and potassium (K) in hill pastures grazed by sheep.Single dung or urine events in winter boosted pasture production by 37% and pasture uptake of S, N and K by up to 35%, 55% and 57%, respectively, during the following year. Whereas the late summer single superphosphate application increased late spring and mid summer pasture growth of the following year only, dung or urine return increased pasture growth in every season of the following year. Despite the addition of 11.5, 4.7 and 376 kg of readily available S, N and K ha-1 in a single dung event and 14.5, 28.5 and 146 kg of S, N and K ha-1 in a urine event, accelerated leaching of S, N and K did not occur from dung or urine affected soil. Less than 3 kg S, 0.5 kg N and 2 kg K ha-1 were lost by leaching from dung or urine affected soil. The majority of S, N and K from excreta remained in the soil, either immobilized in soil organic matter and/or adsorbed on to soil sesquioxide surfaces and cation exchange sites with the equivalent of only 1.6% of S, 4.4% of N and 9.0% of K from dung and 29% of S, 18.7% of N and 31% of K from urine being recovered in increased pasture uptake over a period of one year. Under the climatic conditions that prevailed after the winter deposition of excreta, immediate loss of excreta-derived nutrients was negligible but urine deposition markedly accelerated the leaching losses of native soil calcium and magnesium (8 kg Ca and 2.9 kg Mg ha-1 from urine and 6.4 kg Ca and 2.4 kg Mg from dung, respectively). Quantitative information of this kind is important for determining the long-term sustainability of soil fertility in grazed pastures before a comprehensive understanding of pasture nutrient cycles is complete.
Temporal variation of hydraulic properties for some soils with fragile structure
Authors: Murphy BW , Koen TB , Jones BA , Huxedurp LM
Published: April 2005

At three locations in the wheat belt of N.S.W. Cowra, Junee and Tamworth, soil hydraulic properties were measured through the growing season on hardsetting soils with different tillage histories, namely direct drilling and traditional tillage. The hydraulic properties measured were hydraulic conductivity and sorptivity at -10 and -40 mm tension. Results show that the hydraulic properties of these soils can vary significantly through the growing season. This temporal variability was attributed to tillage, plant growth, rainfall and soil settling under wetting. The soil which had the more severe tillage treatment prior to sowing, together with stubble burning (traditional tillage), had lower values of hydraulic properties at 10 mm tension than the soil with the more conservative tillage treatment of direct drilling. Results for hydraulic properties at 40 mm tension did not show consistent differences between tillage treatments, the tillage effects being dependent on the particle size distribution of the soil and aggregate stability. Overall, the hydraulic properties measured at 10 mm tension did show differences which can be attributed to tillage or soil management, and these differences are most obvious when measurements are made on a settled seedbed in the period from flowering to post harvest.
Estimates of erosion on potato lands on krasnozems at Dorrigo, NSW, using the Cesium-137 technique
Authors: Elliott GL , Coleclark BE
Published: April 2005

A paddock typical of those used for potato cultivation with respect to soils, topography and management was sampled in a grid pattern to determine the redistribution in the soil of the environmental isotope, caesium-137. The total erosion in this paddock, which had been used to grow three spring crops of potatoes in rotation with kikuyu-based pasture, was estimated from the proportional change of caesium-137 content relative to the content in a local, stable reference site. Over the sampled area (3.2 ha), total erosion was estimated to average 297 t ha-1, equivalent to 98 t ha-1 per crop. Comparative erosion estimates were made from the results of single transect sampling in a paddock used for two potato crops and in one under permanent pasture. Results suggest erosion rates of 57 t ha-1 per crop in the former site and 0.09 t ha-1 year-1 in the latter site.
Mobility of phosphate from waste water in calcareous sands of Rottnest Island (WA)
Authors: Gerritse RG
Published: April 2005

Natural levels of inorganic phosphate in soils of Rottnest Island are quite high: about 300 mg/kg as P (or about 4 t of P per ha per meter depth of soil). In comparison, the production of phosphorus in wastewater from sewage, treated on Rottnest Island, amounts to approximately 2 t per year. The phosphate, occurring in the soil naturally, is mainly in mineral form and not very soluble. Solution concentrations in the soils are less than 0.001 mg/L P-PO4 (at pH values of 8.5-8.9). Conditions in the calcareous soils of Rottnest Island are favourable for precipitation of phosphate as calcium phosphates. Theoretically >>99% of phosphate in wastewater from treated sewage can be stored indefinitely as hydroxy-, fluoro- and chloro-apatites. In practice, however, application of wastewater to these soils will result in a (kinetically defined) finite concentration of phosphate to move through the soil slowly as a sharp front. The effective width of the frontal zone was taken to be equal to the longitudinal hydrodynamic dispersivity. Mobilities, relative to water, of fronts resulting from step increases of phosphate in soils were then calculated with an experimentally obtained, time-dependent, adsorption equation and the average residence time of phosphate in the frontal zone. Calculated mobilities were verified experimentally by leaching phosphate through small columns of soil at different concentrations of phosphate and rates of infiltration. For concentrations in wastewater between 10 and 15 mg/L P-PO4, mobilities of phosphate, relative to water, in soils of Rottnest Island are less than 2% for expected infiltration rates of wastewater between 0.5 and 1 cm/day.
A comparison of soil acidification and aluminum under Eucalyptus forest and unimproved pasture
Authors: Prosser IP , Hailes KJ , Melville MD , Avery RP , Slade CJ
Published: April 2005

A comparison was made of pH (1:5, soil: 0.01 M CaCl2) and easily extractable forms of Al [0.01 M CaCl2 (Alca); 1 M KCl (AlK); and 0.05 M CuCl2 (AlCu)] between forest and pasture soils near Bendigo, Victoria. Perennial pasture growth is required in this region to reduce groundwater recharge as part of the management of dryland salinity, but pasture growth may be inhibited by Al and Mn toxicity as a consequence of soil acidification. Both forest and pasture soils were found to be acidic (mean pH of 4.0 and 4.3 respectively) and AlCa concentrations are sufficient to anticipate toxicity to sensitive species. The forest site was cleared of timber over 50 years ago, and has since acidified by 63 kmol H+ ha-1, which is accounted for by organic anion accumulation in the forest regrowth. The forest soil has lower concentrations of AlCa, for a given pH, and more Al complexed to organic matter (Alcu-AlK), even though forest and pasture soils have equal amounts of organic carbon. The different A1 concentrations in forest and pasture soils are accounted for by a lag in A1 response to acidification, and greater complexation of Al with organic matter in the forest soil.
The influence of pH on the forms of cadmium in four West Australian soils
Authors: Mann SS , Ritchie GSP
Published: April 2005

The forms of cadmium in soils affect its uptake by plants and hence its potential toxicity to animals and humans. We studied the effect of pH on the forms of native and added Cd in four West Australian soils which differed in their clay, hydrous oxide and organic matter content. The forms of Cd were extracted sequentially by KCl, BaCl2, NaOCl, ammonium oxalate and concentrated acids. The majority of Cd applied to a sandy soil was found in the soluble (KCl) and the exchangeable (BaCl2) forms at all pH values. In the siliceous sand, the proportion of the Cd present in the exchangeable form increased as the soil solution pH increased. However, in the peaty sand, the opposite trend was observed; at pH 5, approximately 50% of the Cd was found in the exchangeable form, while at higher pH values, < 60% was bound to organic matter and 20% was in the soluble form. In soils in which the main adsorption surface was dominated by hydrous oxides (mainly goethite), 50-70% of the Cd was extracted as bound to oxides and as the residual fraction at pH < 5. At pH values > 5, the majority (90%) of it was extracted in these forms. Soils, containing clay (mainly kaolinite) as the major adsorbent, retained Cd mainly in exchangeable form at all pH values and at all the rates of Cd application. At pH > 5, however, some of the Cd was also found in the residual form and bound to organic matter. This work has shown that the form of added Cd in a soil cannot be elucidated by considering the major adsorbing component alone. It is also necessary to know the pH, the presence of other adsorbing surfaces and the rates of applied Cd.
Effects of phosphate fertilizer applications on microorganisms in pastoral soil
Authors: Sarathchandra SU , Lee A , Perrott KW , Rajan SSS , Oliver EHA , Gravett IM
Published: April 2005

Microbial and earthworm populations and some soil chemical characteristics were measured in soil samples collected from an existing fertilizer trial that had been in progress for 3 years. The samples were collected two weeks before and two weeks after the annual applications of single superphosphate (SSP) or North Carolina phosphate rock (NCPR). There were no significant long-term fertilizer effects on any of the characteristics measured but there were some significant changes between the two samplings. Total bacterial count (69 x 106 to 6 x 106 g-1 soil) and the fungal count (l3 x 105to 5.2 x 105 g-1 of soil) declined significantly in all treatments between the two samplings. This decline was significantly smaller for fungi in fertilized plots. There were significant increases in populations of gram negative bacteria (28 x 105 to 52 x 105 bacteria g-1 of soil) and phosphate rock (PR) dissolving bacteria (7 6 x 105 to l3 x 105 bacteria g-1 of soil) two weeks after fertilizer application. Populations of these bacteria did not change significantly in unfertilized plots. The water-extractable carbon declined significantly in unfertilized and SSP-treated plots but not in NCPR-treated plots. The levels of ammonium oxidizing bacteria, PR-dissolving fungi, fluorescent Pseudomonas spp. and microbial P were unaffected by fertilizer. Two groups of earthworms were examined once before the fertilizer application. There were no significant fertilizer effects on adult or juvenile populations of Lumbricus rubellus or Aporrectodea caliginosa.
Effects of tillage and stubble residue treatments on termite activity in two central Queensland vertosols
Authors: Holt JA , Robertson LN , Radford BJ
Published: April 2005

The effects of tillage and stubble residue management practices on the activity and composition of the termite fauna of some central Queensland Vertosols has been examined, using a combination of spade sampling, baiting and deep coring techniques. Uncultivated Vertisols , previously thought to be devoid of termites, are now known to support at least five species of subterranean termites. They are Amitermes obtusidens Mjoberg, A. agrilus Gay, Microcerotermes serratus (Froggatt), Heterotermes paradoxus (Froggatt) and Termes sp. Clearing and cultivation for dryland cropping virtually eliminated termites from these soils. The adoption of zero till and stubble retention practices however, resulted in the re-appearance of subterranean termites. The implications of increased termite activity in cropping soils are also discussed.
Effect of clay mineralogy and exchangeable cations on water repellency in clay-amended sandy soils
Authors: Ward PR , Oades JM
Published: April 2005

Artificial water-repellent sands were prepared in the laboratory from acid-washed sand and either cetyl alcohol or organics extracted from a natural water-repellent sand. Added clays (at 0.5% w/w) had no effect when gently mixed with a natural and the two artificial water-repellent sands. After a wetting and drying cycle, kaolinite reduced repellency to a low level in the natural sand and the artificial sand with extracted organics, but montmorillonite was not effective. Na+-saturated clays were generally more effective than Ca2+-saturated clays. In the cetyl alcohol sand, montmorillonite was more effective than kaolinite. Neither artificial sand was a perfect model of the natural system, although the extracted organic model was far superior. Kaolinite did not strongly adsorb hydrophobic molecules, but was effective because it was able to cover the hydrophobic sand surface. Application of kaolinite clay to a water-repellent sand appears promising.