Showing papers on "Soil organic matter published in 1979"
TL;DR: Soil-water equilibrium data suggest that the transfer of nonionic chemicals from water to soil may be described in terms of a hypothesis of solute partitioning in the soil organic matter.
Abstract: Soil-water equilibrium data suggest that the transfer of nonionic chemicals from water to soil may be described in terms of a hypothesis of solute partitioning in the soil organic matter. This concept allows estimation of soil-water distribution coefficients either from solvent-water partition coefficients or aqueous solubilities.
1,028 citations
TL;DR: In this article, the authors studied the influence of vegetation burning (ash and heat) on the soil environment and their relation to nutrient availability, and the relationship between ash deposition and soil fertility.
Abstract: 2.3 Changes in soil temperatures after fire 3. Influence of the products of vegetation burning (ash and heat), on the soil environment, and their relation to nutrient availability 3. 1 The soil as an environment for biological activities and nutrient transformations 3.2 The ash component 3.2.1 Relationship between ash deposition and soil fertility 3.2.2 Effects of ash on nutrient cycling and soil chemical and biological processes 3.2.2.1 Ash formation 3.2.2.2 Ash return and properties 3.2.2.3 Nutrient return in ash, and the effect of ash on soil chemical properties 3.2.2.4 Influence of ash on soil biological processes 3.3 The heat component 3.3.1 General introduction 3.3.2 Plant growth in heated and sterilized soils 3.3.3 Effect on soil physical properties 3.3.4 Influence of heat on soil chemical properties 3.3.4.1 Changes in properties other than N compounds 3.3.4.2 Non-biological changes in soil N fractions 3.3.5 Biological changes in heated soils 3.3.6 Non-biological gas exchange in heated soils
709 citations
TL;DR: The allocation of biomass and the turnover time of various components were measured from August 1976 to August 1977 in a young, second-growth Douglas-fir stand in the Oregon Coast Range.
Abstract: The allocation of biomass and the turnover time of various components were measured from August 1976 to August 1977 in a young, second-growth Douglas-fir stand in the Oregon Coast Range. Allocation of biomass among the tree components was 14 732 kg foliage ha−1, 30 455 kg branches ha−1, 212 941 kg boles ha−1, 49 289 kg nonmycorrhizal roots ha−1, and 15 015 kg host portion of mycorrhizae ha−1. Biomass allocation of fungal components was 10 009 kg mycorrhizal mantles ha−1, 2785 kg Cenococcumgeophilum sclerotia ha−1, 65 kg sporocarps ha−1, 369 kg litter hyphae ha−1, and 6666 kg soil hyphae ha−1. The forest floor was composed of 6970 kg fine ( 25 mm) litter ha−1. Soil organic matter (<0.494 mm) was 87 600 kg ha−1. Total annual stand throughput was 30 324 kg ha−1, excluding soil organic matter throughput. Of this total, 50.5% was accounted for by fungal throughput, 39.5% by tree throughput, and 10.0% by forest floor throughput.
236 citations
TL;DR: In this paper, the mechanical strength of sandy soils under radiata pine plantations was measured with a penetrometer, and the importance of organic matter in maintaining a favorable structure in sandy soils and its relation to maintenance of site productivity was discussed.
Abstract: The mechanical strength of sandy soils under radiata pine plantations was measured with a penetrometer. Resistance to penetration was largely independent of water content in the range sampled, and was directly related to the bulk density of the soil. Soil strength at constant bulk density increased with depth owing to increase in overburden pressure and to a decrease in soil organic matter. Soil under native scrub was consistently less compact than that from adjacent radiata pine plantations on the same soil type. Soil from pasture was usually more compact in the surface 20 cm of soil than that from pine plantations, but was less compact at depth. Soil from second rotation plantations was more compact than soil on some first rotation sites, but on other sites no differences could be established. Radiata pine roots preferentially penetrated areas of lower soil strength. Root penetration was severely restricted above a critical penetration resistance of about 3000 kPa. Saturated soils were highly compacted even by light loads in a laboratory consolidometer compared to unsaturated soil. In the unsaturated condition compaction was greatest under heavy loads on soils at about 1% organic matter. Causes of the observed compaction in the field are discussed and remedial measures are suggested. Soil compaction reduced porosity but had little effect on water storage capacity. Increased organic matter at constant bulk density also reduced porosity, but greatly increased water storage capacity and unsaturated hydraulic conductivity. The importance of organic matter in maintaining a favourable structure in sandy soils and its relation to maintenance of site productivity is discussed.
197 citations
Journal Article•
TL;DR: Although soil trematodes probably contribute less than 1% to soil respiration they may play an important role in nutrient cycling in the soil through their influence on bacterial growth and plant nutrient availability.
Abstract: There has been much work on plant-feeding nematodes, and less on other soil nematodes, their distribution, abundance, intrinsic properties, and interactions with biotic and abiotic factors. Seasonal variation in nematode fauna as a whole is correlated with factors such as moisture, temperature, and plant growth; at each site nematode distribution generally reflects root distribution. There is a positive correlation between average nematode abundance and primary production as controlled by moisture, temperature, nutrients, etc. Soil nematodes, whether bacterial feeders, fungivores, plant feeders, omnivores, or predators, all influence the populations of the organisms they feed on. Although soil trematodes probably contribute less than 1% to soil respiration they may play an important role in nutrient cycling in the soil through their influence on bacterial growth and plant nutrient availability.
187 citations
179 citations
146 citations
Book•
01 Jan 1979
TL;DR: In this paper, the authors present a survey of the soil environment and its processes, including the formation of soil, water and the hydrologic cycle, aeration, and profile development.
Abstract: Part 1 The soil habitat: Introduction to the soil The mineral component of the soil Soil organic matter Peds and pores. Part 2 Processes in the soil environment: Soil formation Soil water and the hydrologic cycle Reactions at surfaces Soil aeration Processes in profile development. Part 3 Utilization of soil: Nutrient cycling Maintenance of soil productivity Agricultural chemicals and the soil Problem soils Soil survey and classification.
128 citations
TL;DR: In this article, a water balance model for pasture is described, which takes into account the effect of soil water deficits on evapotranspiration, and is used to assess whether growth would occur on a given day, and to predict unirrigated pasture growth rates for the period December-April of each irrigation season.
Abstract: A water balance model for pasture is described, which takes into account the effect of soil water deficits on evapotranspiration. Data from small lysimeters were used to evaluate methods for the estimation of weather-controlled evapotranspiration from well-watered pasture. The relatively simple Priestley and Taylor method was found to be as accurate as the Penman method or the use of Class A pan data. Three years of computed water balance data were found to agree within 40 mm with the soil water deficits measured with a neutron moisture probe. The computed soil water balance was used to assess whether growth would occur on a given day, and to predict unirrigated pasture growth rates for the period December-April of each irrigation season. Predicted and measured pasture growth rates were in reasonable agreement, with the December-April growth rate on unirrigated pasture averaging only half that for irrigated pasture over the four years of the study.
100 citations
TL;DR: In this paper, the sorption of low concentrations of cadmium by the calcium-saturated <2 µm fraction of four soils was studied in the presence of variable concentrations of calcium and zinc, as a model of reactions in contaminated soils.
Abstract: The sorption of low concentrations of cadmium by the calcium-saturated <2 µm fraction of four soils was studied in the presence of variable concentrations of calcium and zinc, as a model of reactions in contaminated soils. The sorbed cadmium and zinc was determined by radioisotopic procedures and partitioned experimentally into specifically and non-specifically sorbed forms. With cadmium the non-specifically sorbed form usually exceeded specifically sorbed. Specific sorption of cadmium was depressed by competition with zinc but not the reverse. The non-specifically sorbed component of sorbed cadmium, as defined by rapid exchange with calcium nitrate solution, was preferred over calcium by the clay exchanger, with separation factors of 4-10 for cadmium saturations of <1% CEC. Some implications for the management of soil as a sink for heavy metal pollutants are discussed.
TL;DR: In this article, seven buffering indices were evaluated by determining the additional variance accounted for when each index was added to a regression of plant phosphorus uptake on labile soil phosphate, and three of the most effective and consistent indices were a simple index of the maximum buffer capacity, determined from the Langmuir isotherm over a standard range of equilibrium solution concentrations, the slope of the natural solution concentration, and the amount of adsorption at a standard equilibrium concentration of 0.3 pg phosphorus/ml.
Abstract: Seven phosphate buffering indices were evaluated by determining the additional variance accounted for when each index was added to a regression of plant phosphorus uptake on labile soil phosphate. The study was done on two groups of soils: one relatively homogeneous group of 24 soils all formed on the same parent material, and a heterogeneous group of 30 soils formed on a variety of parent materials. A separate pot experiment was done on each group, ryegrass being grown on the homogeneous soils and white clover on the heterogeneous soils. Only two indices did not account for a large and significant increase in variance in phosphate uptake. The extra variance accounted for was much greater in the heterogeneous group than in the homogeneous group, although the total variance accounted for by both variables was greater in the homogeneous group. The much smaller volume of soil used in the ryegrass experiment may explain the smaller buffering effect in the homogeneous soils. The three most effective and consistent indices were a simple index of the maximum buffer capacity, determined from the Langmuir isotherm over a standard range of equilibrium solution concentrations, the slope of the isotherm at the natural solution concentration, and the amount of adsorption at a standard equilibrium concentration of 0.3 pg phosphorus/ml.
TL;DR: In this paper, an intermediate resolution model of the decomposition of soil organic matter is developed from a comprehensive study of published experimental work, where many organic and inorganic forms of soil N, P, and K are mathematically treated, together with the various transformations between forms.
Abstract: An intermediate resolution model of the decomposition of soil organic matter is developed from a comprehensive study of published experimental work. The many organic and inorganic forms of soil N, P, and K are mathematically treated, together with the various transformations between forms. Most of the transformations are moderated by microbes, and the dynamics of the microorganisms are explicitly represented. A simulation is made of a general heterotrophic population using organic C and N for energy, as well as nitrifiers which oxidize nitrogenous compounds chemotrophically. Such explicit treatment of microbe dynamics permits among other things the study of microbe immobilization of important plant nutrients. In addition to the simulation of biological aspects of decomposition, the model treats the physicochemical processes of precipitation, fertilizer and native mineral inputs, leaching loss, sorption of organic and inorganic ions on soil colloids, condensation between organic N and aromatic compounds, and exchange reactions. Model parameters are dealt with in detail in order to base them as firmly as possible on experimental information. The process rates include functional dependence on soil temperature and moisture. For clarity of presentation, the model is divided into four submodels, one each for N, P, and K, and the C energy substrate. The total model is coupled with a previous plant growth model, and thereby simulates complete element cycles within the plant-soil system.
TL;DR: In this article, a number of sites and depths to 300 cm within four great soil groups (krasnozem, red earth, xanthozem, and podzolic) were collected from a series of sites in the UK.
Abstract: Soil was collected from a number of sites and depths to 300 cm within four great soil groups (krasnozem, red earth, xanthozem, podzolic). Nitrate, chloride and sulfate adsorption were determined at the soil pH. Various soil properties likely to influence the magnitude of adsorption were determined, and their relative importance to adsorption was assessed using stepwise multiple regression. The subsoils of all four soil groups adsorbed nitrate ranging up to 0.47 mmoles/100 g from 0.005 M potassium nitrate solution. The mean adsorption for soil groups decreased in the order krasnozem, xanthozem, red earth and podzolic. Chloride and sulfate adsorption was largely equivalent to that of nitrate. The variations in adsorption between and within great soil groups could be attributed to changes in organic matter, smectite minerals, hydroxy aluminium, surface area and pH.
TL;DR: In this paper, the authors found that regularly ploughed and stocked soil in the Western Australian wheatbelt was, with one exception, more compact and less permeable to water than virgin soil.
Abstract: Regular ploughing and stocking physically alter the soil. We hypothesized that these practices render soil unsuitable for large soil animals, and that the presence of large soil animals in turn enhances soil friability and infiltration of water. We found that regularly ploughed and stocked soil in the Western Australian wheatbelt was, with one exception, more compact and less permeable to water than virgin soil. Soil which had not been ploughed or stocked for seven years was as permeable to water as virgin soil, but was intermediate in compaction between virgin and cultivated soil. Virgin soils had more cavities and burrows, as well as more water-stable aggregates, than cultivated soils. Large soil animals were virtually eliminated from the regularly cultivated soils. There was little difference in the number of large soil animals between virgin soil and adjacent soil last cultivated and stocked in 1969. In summer, few large soil animals were found in any soil sampled. These findings are in agreement with the hypothesis stated above.
TL;DR: The complex aromatic ring structures became more resistant to microbial attack during flooding, and the importance of amino acids and carbohydrates in the carbon metabolism by the micrbial community increased.
Abstract: Changes in the microbial activities during and after flooding of Pahokee muck were examined and compared to variations in soil samples incubated under anaerobic conditions in the laboratory. Overall aerobic metabolism, as measured by 14C-labeled succinate oxidation, in the field decreased approximately 65 percent during the first 10 days of flooding and remained at that level until the field was drained. This compared to an 88 percent decrease in soil incubated anaerobically in the laboratory.Aromatic ring catabolism (salicylate oxidation) was most sensitive to flooded conditions. A 90 percent decrease was detected in the oxidation rate for salicylate during flooding. Catabolic rates of amino acids, glucose, and acetate decreased to a lesser extent. The aerobic and facultative bacterial populations increased approximately threefold during the first 10 days of flooding. These populations then decreased until the field was drained when, again, a threefold increase in the numbers occured. Dehydrogenase activity declined during the first five days of flooding; then it increased continually until the field was drained. At that point, the enzymic activity decreased. These data indicate the decling importance of aerobic carbon metabolism during flooding and suggest an increase in the facultative and anaerobic populations. The complex aromatic ring structures became more resistant to microbial attack during flooding, andt he importance of amino acids and carbohydrates in the carbon metabolism by the micrbial community increased.
TL;DR: Estimates of production, soil respiration and organic matter accumulation are used to provide a preliminary carbon budget for the heathland soil system.
Abstract: SUMMARY (2) Measurements of soil respiration (from five sites) over a period of a year are examined against a series of regression models. An estimate of root production (c. 400 g m - 2 yr - 1 organic matter) is obtained, and the carbon dioxide evolved from the soil is apportioned to different components of the soil organic matter. Root respiration accounts for up to 70%. of the total soil respiration. (3) Measurement of respiration of washed root material suggests that such treatment produces enhanced values (up to c. five times that estimated from the regression models) in the case of Calluna. (4) The data are examined as a time-sequence, and the development of the soil profile is considered in the light of the findings of other authors. (5) Finally, estimates of production, soil respiration and organic matter accumulation are used to provide a preliminary carbon budget for the heathland soil system.
TL;DR: With increasing organic matter there is an increase in nutrient concentrations and in the microbial population and it is suggested that these factors are the basis of the antagonism.
Abstract: Soil organic matter collected from beneath an unburnt stand of Eucalyptus marginata was added in increasing amounts to lateritic soil. Phytophthora cinnamomi incubated in soils containing 50% or more organic matter was extensively lysed, and many of the sporangia produced were abortive.
With increasing organic matter there is an increase in nutrient concentrations and in the microbial population and it is suggested that these factors are the basis of the antagonism.
TL;DR: In this article, the root growth rate varied with soil texture and with tillage level, and root depth in finer-textured soil was only half that of the loamy sand.
Abstract: Soil physical conditions were measured under conventional, minimum and zero soil disturbance cropping systems. Seedbed differences were small in soils cropped after stubble, but significantly different on light sandy soils cropped after pasture. Soil resistance to penetrometer was significantly higher at 10 cm with direct drilling. Soil porosity, and properties dependent upon it, varied more with tillage level on loamy sand than on clay loam soil. Root distributions and associated soil interactions were measured by means of soil cores. Root growth rate varied with soil texture and with tillage level. Soil water contents were at matric potentials well above - 1.5 MPa at 6 weeks, but root depth in the finer-textured soil was only half that of the loamy sand. Root extension rate was restricted by soil strength rather than water shortage in the early part of the growing period. Direct tillage with a triple disk drill reduced root extension rate at both sites in the early phase. Evidence of a compaction pan on the loamy sand is presented.
TL;DR: In this article, the surface soil of the bare sealed area was shown to slake readily under quick wetting in contrast to soil surface under grass cover which did not slake.
Abstract: Stable bare degraded areas exist in the lightly grazed perennial grass understorey existing in the eucalypt woodlands of northern Australia. Examination of these areas showed large differences in infiltration which led to increased runoff from the bare sites. However, there was little difference in soil composition between grass-covered and degraded sites apart from a higher organic carbon content in surface soil under grass. Micromorphological examination showed that soil without grass cover had lost its original open structure in the surface layers, developing a surface seal. The surface soil of the bare sealed area was shown to slake readily under quick wetting in contrast to soil surface under grass cover which did not slake. Heavy grazing of the grass understorey destroyed grass clumps within two wet seasons. Once the clumps were killed the soil surface quickly collapsed to form sealed areas, with the same properties as those occurring in ungrazed sites. The persistence of the bare sealed areas is attributed to seed removal during runoff, high temperatures and low moisture content in the sealed layer, as well as mechanical impedance preventing seedling emergence. As re-establishment of native grasses is difficult in this region, care must be taken in pastoral management to prevent the formation of degraded sites, which may take many years to re-vegetate.
TL;DR: In this article, the profiles of density and soil water retentivity for a Fragiaqualf, the Tokomaru silt loam, were found to correspond with the morphological features, with a bulk density of up to 1670 kg m-3 and a negligible volume of macropores in the C horizon fragipan.
Abstract: The profiles of density and soil water retentivity for a Fragiaqualf, the Tokomaru silt loam, were found to correspond with the morphological features, with a bulk density of up to 1670 kg m-3 and a negligible volume of macropores in the C horizon fragipan. The saturated hydraulic conductivity at undrained sites was as low as 0.1 mm day-1 in the B horizon, although there is evidence that at mole-tile drained sites the effective permeability is much higher. Water movement is non-uniform in the subsoil, apparently due to preferential flow between the large polygonal structure units. Comparison of neutron probe profiles and laboratory soil water retentivity data demonstrated the difficulties in using the latter to estimate the available-water holding capacity of the soil. The main problem was the lack of a clearly defined rooting depth. This was probably due to non-uniform water extraction from the subsoil by pasture roots, because of their preferential distribution between rather than within the large structure units. This made it impossible to correlate the 'permanent wilting point' with a particular soil matric potential.
TL;DR: In this article, field plots amended with variable amounts of lead in the spring of 1969 were resampled after six years to ascertain the extent to which the applied lead had moved from the application zone.
Abstract: Field plots amended with variable amounts of lead in the spring of 1969 were resampled after six years to ascertain the extent to which the applied lead had moved from the application zone. Downward movement of lead occurred and was attributed to leaching as soluble chelate complexes with organic matter, transfer of soil by earthworms and other faunal organisms, translocation in plant roots, or any combination of these. Significant horizontal movement also occurred, primarily as a result of physical transfer of soil through tillage operations. (1 diagram, 5 graphs, 21 references, 1 table)
TL;DR: The performance and characteristics of small, porous cup, soil-water extractors, installed in a soil with known water-transmission properties, are described in this article, where the authors show that under these conditions flow distribution is much closer to that of an unextracted soil than is predicted from soil water flow theory.
Abstract: The performance and characteristics of small, porous cup, soil-water extractors, installed in a soil with known water-transmission properties, are described. Cup conductivities decreased sharply during an 8 week period and, in the absence of other flux limiting factors, would limit water entry in the permeable topsoil but not in the slowly permeable subsoil. Measured cup water uptake however was much less than that predicted from either cup conductivity or soil water transmission properties. This is attributed to flow impedance near the cup walls. Under these conditions flow distribution in a soil with extractor cups would be much closer to that of an unextracted soil than is predicted from soil water flow theory.
TL;DR: The results indicate that the total carbon evolved from the different levels of the soil profile by the microbial community oxidizing the soil organic matter decreased as the depth ofThe soil column increased, but correction of the amount of carbon yielded at each level for the bulk density of that level reveals that the microbial contribution to the soil subsidence is approximately equivalent throughout the soil profiles above the water table.
Abstract: The microbial activity of Pahokee muck, a lithic medisaprist, and the effect of various environmental factors, such as position in the profile and type of plant cover, were examined. Catabolic activity for [7-14C]salicylic acid, [1,4-14C]succinate, and [1,2-14C]acetate remained reasonably constant in surface (0 to 10 cm) soil samples from a fallow (bare) field from late in the wet season (May to September) through January. Late in January, the microbial activity toward all three compounds decreased approximately 50%. The microbial activity of the soil decreased with increasing depth of soil. Salicylate catabolism was the most sensitive to increasing moisture deep in the soil profile. At the end of the wet season, a 90% decrease in activity between the surface and the 60- to 70-cm depth occurred. Catabolism of acetate and succinate decreased approximately 75% in the same samples. Little effect of crop was observed. Variation in the microbial activity, as measured by the catabolism of labeled acetate, salicylate, or succinate, was not significant between a sugarcane (Saccharum officinarum L.) field and a fallow field. The activity with acetate was insignificantly different in a St. Augustine grass [Stenotaphrum secundatum (Walt) Kuntz] field, whereas the catabolism of the remaining substrates was elevated in the grass field. These results indicate that the total carbon evolved from the different levels of the soil profile by the microbial community oxidizing the soil organic matter decreased as the depth of the soil column increased. However, correction of the amount of carbon yielded at each level for the bulk density of that level reveals that the microbial contribution to the soil subsidence is approximately equivalent throughout the soil profile above the water table.
TL;DR: In this article, a critical examination of the various methods frequently used to assess soils' potential to retain viruses is presented, with the aid of examples of land application sites across the country, the relationship between laboratory and field studies.
Abstract: The U.S. Water Pollution Control Act Amendment of 1972 (PL 92-500) has made land disposal of wastewater effluents and residuals a viable and attractive alternative (Thabaraj, 1975; Wright, 1975). Land spreading of wastewater effluents and residuals has many advantages, inclding the addition of plant nutrients, water conservation, improvement of soil physical properties, and increased soil organic matter. Public health risks associated with land disposal of wastes containing human pathogens can be assessed only through a thorough examination of the survival and transport pattern of these pathogens through soils. This topic has been thoroughly covered in recent reviews (Bitton, 1975, 1979; Burge and March, 1978; Foster and Engelbrecht, 1973; Gerbaet al., 1975) and need not be examined any further. In this review, we are primarily concerned with a critical examination of the various methods frequently used to assess soils' potential to retain viruses. Knowledge concerning the transport pattern of viruses through soils can be gained through field monitoring of these infectious particles in wastewater effluents, sludges, soils and groundwater, and/or through soil column experiments. The latter have been criticized and our purpose is to examine these criticisms and suggest, if necessary, some alternate solutions. Furthermore, we will review the practical information gained through soil column studies and examine, with the aid of examples of land application sites across the country, the relationship between laboratory and field studies.
TL;DR: In this paper, the influence of soil organic matter on the initial and residual phytotoxicity of thirteen s-triazine herbicides was investigated in greenhouse experiments using three Horotiu sandy loam soils with organic matter levels of 98, 155, and 206% The amount of herbicide required to reduce the growth of oats (Avena sativa L 'Mapua'), when compared with the control was determined for each her- bicide and each organic matter level.
Abstract: The influence of soil organic matter on the initial and residual phytotoxicity of thirteen s-triazine herbicides was investigated in greenhouse experiments using three Horotiu sandy loam soils with organic matter levels of 98, 155, and 206% The amount of herbicide required to reduce the growth of oats (Avena sativa L 'Mapua') by 50% (GR5 0) when compared with the control was determined for each her- bicide and each organic matter level Results showed that the GRS5 values for all herbicides were highly and positively correlated with the soil organic matter In general, the phytotoxicity of compounds of high water solubility was less influenced by soil organic matter than those having low water solubility The chloro-triazines persisted longer in soil than did the methoxy- or methylthio-triazines Simazine (2-chloro- 4,6-bis(ethylamino)-s-triazinel and atrazine (2-chloro-4-(ethylamino)-6- (isopropylamino)-s-triazinel were the most persistent of the chloro- triazines Additional index words Avena sativa, persistence, phytotoxicity