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  • 1
    Electronic Resource
    Electronic Resource
    Long-term solute dynamics and hydrology in irrigated slowly permeable soils (1979)
    Springer
    Irrigation science 1 (1979), S. 77-87 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A simple model is given, based on mass conservation of a non-transformed non-absorbed solute or ion (such as the chloride ion), which allows long term trends in the concentration of this solute to be predicted. The method involves solution of an implicit equation for the long term through-drainage flux below the maximum depth of sampling. A knowledge of the initial chloride ion concentration in the soil depth of interest, and its value after a known application via irrigation water provides sufficient information for the model to be applied. The model is applied to data from an irrigated slowly permeable swelling clay soil. A drainage flux of 8 cm yr−1 beneath paddy rice was inferred, and some twenty-five years after commencement of irrigation an equilibrium soil salinity of 22 meq/l at saturation was predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00263091
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  • 2
    Electronic Resource
    Electronic Resource
    Leaching of a sorbed solute: A model for peak concentration displacement (1980)
    Springer
    Irrigation science 1 (1980), S. 169-175 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary An investigation of the downward transport of a solute following a series of alternating irrigation/rainfall and evapotranspiration events is carried out. The principle of conservation of mass, and the concepts of partition chromatography are used in constructing a simple model which enables the peak solute concentration depth to be calculated at any particular time given the rainfall and evapotranspiration history. Prediction of the theory is compared with published data on solute transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270881
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  • 3
    Electronic Resource
    Electronic Resource
    Theory of solute transport in soils from the method of characteristics (1983)
    Springer
    Irrigation science 4 (1983), S. 277-287 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A general theory of vertical solute movement in a soil is presented, which takes into account uptake of water and solute by roots, irrigation or rainfall, and solute application and adsorption by the soil. Irrigation, rainfall, and the surface application of fertilizers are arbitrary functions of time. The main limitation of the theory is the neglect of the variability of soil-water conductivity with position. The theory is illustrated by comparing predictions and experimental observations of solute leaching losses measured in a lysimeter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389650
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  • 4
    Electronic Resource
    Electronic Resource
    Patterns of water withdrawal beneath an irrigated peach orchard on a red-brown earth (1988)
    Springer
    Irrigation science 9 (1988), S. 89-104 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Water withdrawal from the soil beneath an irrigated peach orchard is described over depth and time after irrigation for a red-brown earth where the hydraulic properties vary with depth. Relationships between water uptake by roots, root concentration and soil-water suction were explored over protracted drying cycles. In the early stages of drying water uptake by roots was well correlated with root concentration over the profile but, over time, water uptake was redistributed over the root system. Theoretical analysis suggests that poor utilization of water from depth on this soil was associated mainly with low root concentrations and low root (radial) conductance. Practical considerations for improved water management in the root zone of peach orchards on shallow soils are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262353
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  • 5
    Electronic Resource
    Electronic Resource
    Interpretation of solute profile dynamics in irrigated soils (1990)
    Springer
    Irrigation science 11 (1990), S. 199-207 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The steady-state leaching requirement (LR) model (USSL 1954) and the transient solute mass balance model of Rose et al. (1979) were applied to soil chloride data from 42 sites in Queensland, Australia, to evaluate utility of the models for assessing the impact of irrigation on soil salinity and leaching. Data were taken from previous studies on salinity in irrigated soils, and covered a wide range of soil types and irrigation managements. The time taken for soil chloride levels to reach steady-state was assessed from the transient model, and was calculated to be years (〉 3) or decades. These calculations showed that 19 sites had been sampled prior to steady-state, so that a strict application of the LR model was invalid. However, at only seven of these sites were there significant differences between sampled soil chloride and the calculated final values. At these seven sites leaching fluxes calculated with the two models differed by 3–162 mm y−1. At two sites leaching fluxes were ≤0 and the LR model could not be used to interpret soil chloride dynamics. Although both models assume constant inputs through time, variations in irrigation management practices at most sites had little practical effect on model predictions. However, where there were extreme variations in irrigation application or irrigation water chloride concentration, calculated leaching fluxes and thus predicted chloride levels were markedly affected. These models should not be applied in this situation. The transient model was preferred to the steady-state LR model for assessing the effect of irrigation on soil salinity, because of its ability to provide predictions of future soil chloride levels under non-steady conditions, and where leaching flux values are ≤ 0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190534
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  • 6
    Electronic Resource
    Electronic Resource
    Interpretation of solute profile dynamics in irrigated soils (1990)
    Springer
    Irrigation science 11 (1990), S. 219-225 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Knowledge of the flux of water flowing through macropores in soils is required to devise management strategies for efficient fertiliser use and to prevent fast movement of solutes and pollutants to groundwaters. Water and solute balances in soil profiles were used to develop a simple model for assessing the magnitude of macropore flow. Fluxes of water bypassing the soil matrix were calculated at 35 sites to be between 0 and 415 mm y−1, with the flux being 〈 200 mm y−1 at most sites. The maximum flux was three times the flux flowing through the soil matrix but only one third of that infiltrating the soil. The flux of macropore flow was not simply related to soil types or soil properties, although the highest fluxes did occur in cracking soils. A qualitative method of using soil chloride profiles to indicate the occurrence (but not magnitude) of bypass flux was also demonstrated. Both these quantitative and qualitative assessments of bypass flow should assist in interpreting root-zone hydrology in soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190536
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  • 7
    Electronic Resource
    Electronic Resource
    Interpretation of solute profile dynamics in irrigated soils (1990)
    Springer
    Irrigation science 11 (1990), S. 209-217 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The simple field-oriented convective-dispersive equation based model of Rose et al. (1982a and b) has potential to be used to monitor changes in soil chloride levels on commerical farms. As yet applications of the model have only been reported for detailed studies conducted on coarse textured soils. Here the model was applied to a wider range of soil types using input data likely to be available on commercial farms. The model gave good predictions of measured soil chloride profiles at five sites, which included two spray-irrigated Vertisols. To provide accurate predictions in these two Vertisols, infiltration of rainfall into macropores had to be accounted for (by an approximate means). Values of parameters in the model (including the solute dispersivity coefficient) at these five sites were within the range found in previous studies, even for the Vertisols. Variation in the solute dispersivity coefficient within the extreme values that had been found in this and previous studies, did not greatly affect predicted soil chloride profiles. At another three sites, all flood irrigated Vertisols, predicted soil chloride levels were lower than measured values, regardless of values chosen for model parameters. The effect of depth variation in field capacity and wilting point moisture contents on chloride movement was investigated at these three sites as a possible cause of the inaccurate predictions, and found to have a negligible effect on predicted profiles. Differences between measured and predicted soil chloride levels were attributed to infiltration of irrigation water into cracks and, at one site, to the effects of high watertables. These processes were not represented in the model, explaining the failure in this context. Application of the PEAK model provided useful insights into the root-zone hydrology of all soils studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190535
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  • 8
    Electronic Resource
    Electronic Resource
    Modelling the effect of varying soil water on root growth dynamics of annual crops (1996)
    Springer
    Plant and soil 185 (1996), S. 125-135 
    Details
    ISSN: 1573-5036
    Keywords: cowpea ; models ; root growth ; root distribution ; soil water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We present a simple framework for modelling root growth and distribution with depth under varying soil water conditions. The framework considers the lateral growth of roots (proliferation) and the vertical extension of roots (root front velocity). The root front velocity is assumed to be constant when the roots descend into an initially wet soil profile. The lateral growth of roots is governed by two factors: (1) the current root mass or root length density at a given depth, and (2) soil water availability at that depth. Under non-limiting soil water conditions, the increase in root mass at any depth is governed by a logistic equation so that the root length density (R v) cannot exceed the maximum value. The maximumR v, is assumed to be the same for all depths. Additional dry matter partitioned to roots is initially distributed according to the current root mass at each depth. As the root mass approaches the maximum value, less dry matter is partitioned to that depth. When soil water is limiting, a water deficit factor is introduced to further modify the distribution of root dry matter. It is assumed that the plant is an “energy minimiser” so that more root mass is partitioned to the wetter regions of the soil where least energy will be expended for root growth. Hence, the model allows for enhanced root growth in areas where soil water is more easily available. Simulation results show that a variety of root distribution patterns can be reproduced due to varying soil water conditions. It has been demonstrated that broad patterns of root distribution reported in the literature can also be simulated by the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02257569
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  • 9
    Electronic Resource
    Electronic Resource
    Caesium-137 profiles in the sediments of a partial-meromictic lake on Great Sandy Island (Fraser Island), Queensland, Australia (1983)
    Springer
    Hydrobiologia 103 (1983), S. 21-27 
    Details
    ISSN: 1573-5117
    Keywords: paleolimnology ; caesium-137 ; perched lake ; meromictic ; diffusion ; bioconcentration ; sediment accumulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hidden Lake is a perched, brown-water lake located in the centre of Great Sandy Island (Fraser Is.), S.E. Queensland. It is highly acid (pH 4.0), oligotrophic and is thermally and chemically stratified for most of the year. The sediments revealed a 137Cs profile which departed from the temporal pattern of 137Cs fallout in Brisbane and was represented by an exponential increase of 137Cs towards the surface sediments from ca. 32 cm depth. The possible causes of the divergent profile are discussed, including physical and biological mixing, lag in the transport of catchment material to the sedimentary basin, diffusion, recycling and biological concentration. It is hypothesised that a combination of the last four processes, with diffusion facilitated by the highly acid conditions, are the major causes of the observed 137Cs profile. Possible recycling and bioconcentration of 137Cs raises questions as to the validity of this method of dating in similar environmental conditions, and as to the interpretation of other palaeochemical data. These hypotheses are to be tested against profiles obtained from 14C, 210Pb, 239/240Pu analyses of the sediment, and the measurement of 137Cs activity in the water and biota of the lake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028423
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  • 10
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    Characteristics and Modeling of Runoff Hydrographs for Different Tillage Treatments (2000)
    Wiley
    Details
    Publication Date: 2000-09-01
    Print ISSN: 0361-5995
    Electronic ISSN: 1435-0661
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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