Showing papers in "Soil Science in 1975"
TL;DR: The number of earthworm channels ranging from 2 to 11 mm in diameter were counted to 80 cm depth in tilled and untilled grey-brown podzolic soil derived from loess as discussed by the authors.
Abstract: The number of earthworm channels ranging from 2 to 11 mm in diameter were counted to 80 cm depth in tilled and untilled grey-brown podzolic soil derived from loess. Number and percentage volume of earthworm channels in the Ap horizon approximately doubled during 4 years of no-tillage practic
543 citations
TL;DR: A brief review of the process of bacterial sulfate reduction in respect to other processes in ocean sediments is given in this article, where rates of sulfate reducing have been discussed in the context of control mechanisms and geochemical consequences.
Abstract: A brief review has been given of the process of bacterial sulfate reduction in respect to other processes in ocean sediments. In particular, rates of sulfate reduction have been discussed in the context of control mechanisms and geochemical consequences. It is concluded that besides temperat
345 citations
TL;DR: In this paper, the slow reactions between phosphate and soil were studied by incubating, at a range of temperatures, soils to which phosphate had been added in solution, after various intervals, solutions which were 0.01 M with respect to calcium chloride and which contained phosphate, were shaken briefly.
Abstract: The slow reactions between phosphate and soil were studied by incubating, at a range of temperatures, soils to which phosphate had been added in solution. After various intervals, solutions which were 0.01 M with respect to calcium chloride, and which contained phosphate, were shaken briefly
202 citations
TL;DR: In this paper, an experiment was conducted with cotton (Gossypium hirsutum) at the Auburn rhizotron to test the validity of three assumptions: water uptake was proportional to the water potential difference between root xylem and bulk soil and to the hydraulic conductivity of the combined soil-root pathway.
Abstract: Several mathematical models have been developed to describe water uptake by plant root systems. These models usually incorporate one or more of the assumptions that water is proportional to rooting density, to soil hydraulic conductivity, and to the water potential difference between the root surface and that in bulk soil midway between two adjacent roots. An experiment was conducted with cotton (Gossypium hirsutum) at the Auburn rhizotron to test the validity of these three assumptions. Soil water potential, soil hydraulic conductivity, water uptake, and rooting density were measured or estimated as functions of soil depth and time. Average plant water potential for a water extraction period was estimated from pressure chamber and continuous stem diameter measurements. The assumption that water uptake is proportional to rooting density was valid. However, there appeared to be a large resistance in the pathway from root epidermis to root xylem. The other two assumptions must be modified to include this resistance. Therefore, water uptake was proportional to the water potential difference between root xylem and bulk soil and to the hydraulic conductivity of the combined soil-root pathway. There was no depth-of-roots effect on the validity of these relationships.
156 citations
TL;DR: Alfalfameal, sucrose, and peat moss were added in large amounts to very acid soil to find their effects on yields of barley and alfalfa grown in the greenhouse as discussed by the authors.
Abstract: Alfalfameal, sucrose, and peat moss were added in large amounts to very acid soil to find their effects on yields of barley and alfalfa grown in the greenhouse. Alfalfameal was found to be the most effective. Its action was attributed primarily to complexing of exchangeable Al and, in conseq
149 citations
TL;DR: In this article, the authors discuss adsorption reactions between orthophosphate ions and calcium carbonate and the hydrous oxides, and relationships between the soluble and labile phosphate in soils.
Abstract: This paper discusses adsorption reactions between orthophosphate ions and calcium carbonate and the hydrous oxides, and relationships between the soluble and labile phosphate in soils.
115 citations
TL;DR: In this paper, the mechanisms and products of weathering of felspars, micas, and ferromagnesian minerals are reviewed, with illustrations from mineralogica1 studies on residual soil profiles where unambiguous mineral transformations have been directly observed.
Abstract: Recent ideas and findings on the mechanisms and products of weathering of felspars, micas, and ferromagnesian minerals are reviewed, with illustrations from mineralogica1 studies on residual soil profiles where unambiguous mineral transformations have been directly observed and from experime
113 citations
TL;DR: The natural history of aquatic and sedimentary humic substances in both marine and freshwater environments is reviewed in this article, where the ecological, geological, and economic importance of these compounds are discussed, and attention is drawn to problems requiring further research.
Abstract: The natural history of aquatic and sedimentary humic substances in both marine and freshwater environments is reviewed. The ecological, geological, and economic importance of these compounds is discussed, and attention is drawn to problems requiring further research.
101 citations
TL;DR: In this article, a numerical model based on the transport equations for water and noninteracting solutes and written in IBM S/360 CSMP language was designed to compute the radial movement of water and salts to plant roots.
Abstract: A numerical model, based on the transport equations for water and noninteracting solutes and written in IBM S/360 CSMP language, was designed to compute the radial movement of water and salts to plant roots. The inputs are: the soil's suction and conductivity functions, the soil solution's content and concentration, root density and permeability, and the required uptake rate (whether constant or diurnally fluctuating). The output provides the time-dependent drawdown of matric and osmotic potentials in the immediate vicinity of the root, the gradients and flow rates of water and solutes in the soil, and the plant water potentials needed to maintain different uptake rates. The model is illustrated for various rooting densities and various initial water contents and salt concentrations. The effect of increasing root density and permeability is seen to be similar to the effect of increasing water content or reducing transpirational demand.
TL;DR: In this article, the erodibility index of two tropical soils from Western Nigeria were used to investigate the possibility of using the raindrop technique to determine the soil erodoribility index as compared with soil behavior towards erosion under natural field conditions.
Abstract: Aggregates of two tropical soils from Western Nigeria were used to investigate the possibility of using the raindrop technique to determine the soil erodibility index as compared with soil behavior towards erosion under natural field conditions. Aggregate size, initial soil moisture potential, and raindrop temperature were tested for their effect on the structural stability of the soils. High soil moisture potential (more negative) significantly increased the erodibility of a clayey soil containing expanding lattice clay minerals. The erodibility index of a sandy clay loam soil containing kaolinitic clay minerals and amorphous iron and aluminium oxides was slightly decreased when at high moisture potential. The increase in water temperature increased the erodibility of both soils. Erodibility was found to vary directly with sand and inversely with clay content. A routine laboratory method of evaluating the erodibility of a soil using a rating curve is proposed. /Author/
TL;DR: In this paper, the stability of heavy metal sulfides (MnS, FeS, ZnS and CuS) in aerobic and anaerobic soil was studied, and water extracts of each treated soil were made regularly during a 75-day incubation period.
Abstract: The stability of heavy metal sulfides (MnS, FeS, ZnS, CuS, and HgS tagged with 35S) in aerobic and anaerobic soil was studied. The sulfides are listed in decreasing order of solubility. Water extracts of each treated soil were made regularly during a 75-day incubation period. The radioactivi
TL;DR: The authors showed that substantial amounts of NO3- were reduced to NH4+ after 4 hr of anaerobic incubation, and 15NH4+ continued to increase until all or most of the 15NO3- had been converted to NH 4+, organic N, and gaseous forms (N2 and N2O).
Abstract: Rates of NO3- disappearance under anaerobic conditions, from six widely differing soils, gradually increased and then became relatively constant when glucose was added in increments supplying 004 to 15 mg of C/g of soil Maximum rates of NO3- loss ranged from approximately 93 to 137 percent/hr Increased production of NH4+ accompanied glucose additions in all soils Results based on 13N-labeled Ca(NO3)2 showed that substantial amounts of NO3- were reduced to NH4+ after 4 hr of anaerobic incubation, and 15NH4+ continued to increase until all or most of the 15NO3- had been converted to NH4+, organic N, and gaseous forms (N2 and N2O) Results seriously challenge the prevalent view that denitrification accounts for essentially all NO3- dissimilation in anaerobic soils
TL;DR: In this article, the authors measured the proportion of added phosphate which exchanged with P32 by shaking the soil with solutions which were 0.01 M with respect to calcium chloride and which contained appropriate concentrations of labeled phosphate.
Abstract: Phosplate solutions were added to samples of a soil and the samples were then incubated at a range of temperatures between 4° and 42°C for periods of up to 320 days. After various intervals, the proportion of the added phosphate which exchanged with P32 was measured by shaking the soil with solutions which were 0.01 M with respect to calcium chloride and which contained appropriate concentrations of labeled phosphate. The proportion of the added phosphate which exchanged was found to be independent of the quantity of phosphate added. It decreased with increasing periods of incubation at a rate which depended on the temperature. The effects of time and temperature of incubation were comparable with previously observed effects on the concentration of phosphate in the soil solution and on the decrease in effectiveness of phosphate for plant growth. For a given period and temperature of prior incubation, the proportion of the added phosphate which exchanged was related to a fractional power of the period of equilibration with P32. The effects of level of application, period and temperature of incubation, and period of equilibration could be described by a single equation. It is suggested that the effects observed in this and in preceding papers can be explained if it is assumed that the initial adsorption reaction of phosphate is followed by a further reaction in which a second hydroxyl group of the phosphate reacts with the surface. It is postulated that there is a range of reaction velocities at individual sites. A distribution of reaction velocities which is compatible with the results is presented.
TL;DR: The vertical distribution of microbial adenosine triphosphate (ATP) was determined seasonally for sediments of the salt marsh at Sapelo Island, Georgia.
Abstract: The vertical distribution of microbial adenosine triphosphate (ATP) was determined seasonally for sediments of the salt marsh at Sapelo Island, Georgia. Two study areas were chosen representing major differences in productivity of the marsh grass, Spartina alterniflora. The streamside zone r
TL;DR: In this paper, the authors summarized the present state of knowledge on early diagenesis of organic matter in marine soils and concluded that diagenisation is controlled by biological degradation at the sediment-water interface, organic condensations, organic-metal ion interactions, and organicmineral interactions.
Abstract: With the exception of sediment deposited close to land, organic matter in marine sediments is derived mainly from planktonic debris from the local biomass. Since planktonic material is principally composed of proteins and carbohydrates (hemicellulose), it is of interest to compare the pathway of organic decay in a marine sediment with that of a terrestrial soil where lignin and cellulose is the chief organic input. The article briefly summarizes the present state of knowledge on early diagenesis of organic matter in marine soils. Information is based on the authors studies on distribution of amino acids and sugars in marine sediments deposited under reducing and oxidizing conditions. It is concluded that diagenesis is controlled by (i) biological degradation at the sediment-water interface, (ii) organic condensations, (iii) organic-metal ion interactions, and (iv) organicmineral interactions.
TL;DR: In this paper, the surface boundary condition is taken either as a time-varying flux, time varying water content, or with the flux as a linear function of the water content.
Abstract: Analytical solutions to the one-dimensional, linearized moisture flow equation are presented. The surface boundary condition is taken either as a time-varying flux, time-varying water content, or with the flux as a linear function of the water content. A semi-infinite, vertical flow medium is considered with arbitrary initial conditions. Calculations for a cyclic flux input are compared to the associated nonlinear, finite difference solution for five simulations using data from two soils. The results are encouraging in that the same general profiles are obtained. The solution is believed to have particular merit to describe moisture regimes resulting from a high frequency irrigation schedule.
TL;DR: The results obtained allowed us to assess the importance of the environment, as well as some aspects of overall growth and its modification, in the development of flower and fruit growth.
Abstract: Prefaces Acknowledgements 1. Prolegomena 2. The environment 3. The supply and use of water 4. The absorption and transport of mineral nutrients 5. Photosynthesis and respiration 6, Germination and seeding emergence 7. vegetative growth 8. Flowering and fruit growth 9. Some aspects of overall growth and its modification 10. The prediction of responses Glossary Appendices Index.
TL;DR: In this paper, a reassessment of tillage requirements in terms of soil physical conditions, since these may determine to what extent current or new systems of reduced or zero tillage can be more widely adopted.
Abstract: Recent developments in herbicides and machinery for drilling and cultivation require a reassessment of tillage requirements in terms of soil physical conditions, since these may determine to what extent current or new systems of reduced or zero tillage can be more widely adopted. Soil and cl
TL;DR: Ferromanganese concretions and crusts on the floor of the deep sea are discussed as examples of ores formed in the marine sedimentary environment of the oceans in this article.
Abstract: Ferromanganese concretions and crusts on the floor of the deep sea are discussed as examples of ores formed in the marine sedimentary environment of the oceans. Their properties, the origin of their constituents, and their mode of formation, including the role of microbes in this process, are considered.
TL;DR: In this paper, different sequences of temperature fluctuations between 5° and 35°C imposed upon three soils during incubations of 52 days had no effect upon the amount of N mineralized.
Abstract: Different sequences of temperature fluctuations between 5° and 35°C imposed upon three soils during incubations of 52 days had no effect upon the amount of N mineralized. Over the first 32 days, the results agreed with calculated mineralization rates in all three soils, but only one soil (Barnes) showed agreement for the whole 52-day period. The failure to obtain agreement in Cecil and Kranzburg soils beyond 32 days may be due to the effects of extreme temperature changes upon the ammonifying organisms. The results, however, justify continued efforts to improve means for predicting soil nitrogen mineralization rates in the field.
TL;DR: In this paper, the authors measured the desorption of a series of soils by shaking the soils with a range of volumes of phosphate-free solutions and found that the amount of phosphate which could be desorbed decreased as the period of prior contact between soil and phosphate increased.
Abstract: Known amounts of phosphate were added to a series of soils and, after incubation at constant temperature, desorption was measured by shaking the soils with a range of volumes of phosphate-free solutions. When the method of shaking was vigorous, an initial desorption of phosphate was followed by an apparent resorption. Since this did not happen when shaking was gentle, it was thought to be due to breakdown of soil particles and exposure of new surfaces. When gentle shaking was used, desorption was almost complete within a few hours when the solution:soil ratio was small but continued up to at least 96 hr when the ratio was large. The amount of phosphate which could be desorbed decreased as the period of prior contact between soil and phosphate increased. The rate and amount of desorption could be described by an equation which indicated that the proportion of the phosphate which could be desorbed increased with a fractional power of the period of desorption, and decreased with a fractional power of the period of prior contact. The amount of desorption also depended on intrinsic soil properties and it was found that, for a range of soils, a parameter reflecting desorption was highly correlated with a measure of adsorption.
TL;DR: The successful fitting of the Wilson equation to solid phase activity coefficients for binary aqueous systems makes possible the construction of three-component graphs for the ternary systems as discussed by the authors.
Abstract: The successful fitting of the Wilson equation to solid phase activity coefficients for binary aqueous systems makes possible the construction of three-component graphs for the ternary systems: (Na-Rb-Cs) Wyoming montmorillonite, (Na-Rb-Cs) Chambers montmorillonite, and (Na-K-Cs) attapulgite. Given the composition of the liquid (solid) phase, one can predict the composition of the solid (liquid) phase. The results showed (i) that the ion exchanger in ternary systems still tended to prefer the counter-ion with smaller equivalent volume, (ii) that attapulgite ion-exchange properties were similar to montmorillonites and could be regarded as intermediate between Wyoming and Chambers, and (iii) that soil which contained montmorillonite with low CEC might be more susceptible to becoming sodic than would soil which contained montmorillonites with high CEC.
TL;DR: In this paper, the authors investigated the effect of various factors on the distribution of methane, oxygen and carbon dioxide around a leak, including leakage rate, the depth of the groundwater table, the soil moisture content and the extent of the pavement.
Abstract: Leakage of natural gas from the gas distribution system affects the physical, chemical and biological processes in the soil. Particularly the microbial oxidation of methane is then of predominant importance for the composition of the soil gas phase. The rate of methane oxidation was measured under varying conditions of gas phase composition, temperature and nutrient supply. Computation models were evolved with which it is possible to calculate the effect of these and other factors on the distribution of methane, oxygen and carbon dioxide around a leak. Experiments with actual and artificial leaks as well as the calculations showed that the extent of the gas zone largely depends on the leakage rate, the depth of the groundwater table, the soil moisture content and the extent of the pavement. The soil temperature also proved to have a significant influence by its effect on the microbial methane oxidation. At low temperatures this microbial process is limited and consequently the anaerobic zone, which is invariably present in summer, may then disappear completely, thus making the probability of injury to vegetation negligible in winter. After repair of the leak the poor aeration conditions in the soil may persist for quite a long time. This is caused by the high consumption rate of oxygen required for the oxidation of organic substances and reduced anorganic compounds accumulated in the soil during gas leakage. The oxygen overdemand and the oxidation rate were determined for various gassed soils. Measures can be taken to accellerate soil recovery processes and to improve conditions for regeneration of injured trees and before planting new trees. Both experiments and calculations with computation models proved that installation of open ventilation channels is very effective, even if the leak cannot be immediately repaired. So ventilation channels can also be installed as preventive measure.