Showing papers in "Soil Science in 1986"

Changes in soil carbon storage after cultivation

Abstract: Previously published data from 625 paired soil samples were used to predict carbon in cultivated soil as a function of initial carbon content. A 30-cm sampling depth provided a less variable estimate (r2 = 0.9) of changes in carbon than a 15-cm sampling depth (r2 = 0.6). Regression analyses of chang

Predicting the water-retention curve from particle-size distribution: 1. sandy soils without organic matter1

Abstract: We present a simple model for predicting the water-retention characteristics of sandy soils from routinely available textural and structural soil properties.Using the basic concept of shape similarity between the retention curve h(θ) and the cumulative particle-size distribution function F(d

A resistance parameter for bare-soil evaporation models

Abstract: A bare-soil surface resistance parameter significantly improved the fit of a numerical model of heat and moisture flow in soils to 3 days of field measurements. The resistance removed a positive bias from the model estimates of daily cumulative evaporation on days with minimum surface soil moisture

Hydraulic conductivity and related physical properties of peat, lost river peatland, northern minnesota

Abstract: We measured hydraulic conductivity (K), bulk density, and humification of peat in three soil profiles at a spring fen-raised bog complex in the Lost River Peatland, northern Minnesota. Piezometers were installed at saturated depths ranging from 0.5 to 3.0 m on a raised bog, its external fen margin,

Simple partitioning of anions and dissolved organic carbon in a forest soil

Abstract: We analyzed the adsorption characteristics of B horizon soil of a Spodosol (Fragiorthod) as part of a series of studies to evaluate the importance of adsorption processes to nutrient cycling at the Hubbard Brook Experimental Forest, New Hampshire. The results of equilibration experiments using natur

The occurrence of interlayer clay-organic complexes in two New Zealand soils

Abstract: By using x-ray diffractometry and /sup 13/C-NMR spectroscopy, in combination with chemical and heat pretreatments, the authors have found good evidence for the occurrence of interlayer clay-organic complexes in two New Zealand soils. Here, the clay mineral is a regularly interstratified mica-smectite, and the organic species is a humic substance with a polymethylene chain structure. The organic material in the complex is resistant to peroxidation and pyrophosphate extraction. It is also thermally stable, being extensively decomposed only after the complex is heated at 400/sup 0/C. A combination of soil factors seems necessary for interlayer complex formation. This includes a smectitic clay mineralogy, an accumulation of organic matter associated with a low microbial activity, and a highly acid soil reaction.

The Effect of ph on Sulfate Adsorption by a Forest Soil

Abstract: Acidic deposition and forest clear-cutting are disturbances that have resulted in increased acidification of northeastern forest ecosystems. This study was conducted to evaluate whether acidification processes that are important in regulating sulfate transport and cycling in a Spodosol at the Hubbard Brook Experimental Forest, New Hampshire. The results of adsorption experiments demonstrated that small changes in solution pH have a large effect on sulfate adsorption characteristics of mineral soil at Hubbard Brook. The ability of the soil to remove sulfate from solution increased as the pH of the solution was decreased, with a maximum removal occurring at about pH 4.0. Through the use of initial mass isotherms, it was determined that sulfate removal depended upon (1) the ability of the soil to partition sulfate between the soil and solution phases and (2) the amount of reactive native sulfate that is present in the soil. Our analysis demonstrated that both these soil properties depend strongly upon solution pH.

Dissolution of feldspars by low-molecular-weight aliphatic and aromatic acids

Abstract: Calcic plagioclase (An69 Ab30), albite (An6 Ab94), and microcline (An2 Ab31 Or67) were leached over a 10-wk period at 13°C with 10−4M solutions of a number of low-molecular-weight organic acids. The effectiveness of the organic acids in dissolving the feldspars was found to be citric ≈ oxalic > sali

Comparison between suction and free-drainage soil solution samplers1

Abstract: In this study we compared the ability of porous ceramic cups and a newly developed pan sampler to monitor chloride movement through the following three soils of diverse texture: a Grossarenic Paleustalf, a Typic Udifluvent, and a Udic Chromustert. Two pan samplers and three suction cups were install

Residual Effects of Tillage on Coastal Plain Soil STRENGTH1

Abstract: It has been suggested that different tillage methods create soil physical conditions that persist for various lengths of time in the easily compacted soils of the Southeastern Coastal Plain. To test this hypothesis, plots that had been subsoiled and chiseled were conventionally treated (disk-harrowed) for 1 to 3 yr to observe the residual effect of deeper tillage. In the final season, penetration resistances of all plots were measured at field capacity over a 1.90− x 0.55-m cross-sectional cut of soil perpendicular to the rows. This allowed plotting the isostrength patterns of the soil profile of each treatment. Although some residual subsoil tillage effect could still be identified 2 yr after subsoiling, the increase in soil strength (cone index) to 1.5 to 2.5 MPa even after a single year and the inability to position planters precisely over the previous yearʼs subsoiled rows negated any benefit from the previous yearʼs tillage.

Preexisting channels and soybean rooting patterns

Abstract: We used a trench-profile method to study soybean (Glycine max (L.) Merr.) root distribution and vertical channel patterns in Flanagan (Aquic Argiudoll) silt loam. Root distribution was quantified as the number of first-order lateral roots, the depths at which tap and first-order lateral roots encountered burrows, and the maximum rooting depth where white, young roots with growing tips occurred. In this work, we called all round vertical channels in the soil burrows, not attempting to determine whether they had been made by worms, insects, or roots. Numbers per unit area and diameters of burrows were measured at 20-cm-depth increments from 10 to 130 cm. The first-order lateral roots occurred in the top 30 cm of the soil, and most roots encountered burrows at 30 to 45 cm below the surface. If a taproot failed to encounter a burrow at this level, the root tip died. Once in a burrow, the root grew downward within the channel to the point at which the burrow ended. The number of burrows with diameters greater than 1.5 mm increased with increasing depth from the surface to about 40 cm, then decreased, with very few burrows below a depth of 130 cm. Under sod, the same trend in distribution was observed, but with more burrows below 50 cm than were seen under soybeans. The number of burrows at a depth of 30 cm ranged from 500 to 1400 m−2. The maximum total cross-sectional area of burrows at the 30-cm depth was about 0.007 m2 m−2 of soil surface. The numbers of burrows, with the tendency of roots to grow in these burrows, suggest that burrows have a profound effect upon the shape of the root system, as well as upon rapid gas and water movement.

Effects of Soluble Organic Matter and Sewage Sludge Amendments on Cadmium Sorption by Soils at Low Cadmium Concentrations

Abstract: The authors investigated cadmium sorption by soils of different chemical and mineralogical composition at soil solution concentrations between 0.001 and 12 ..mu..mol Cd kg/sup -1/. The application of municipal sewage sludge to the soils generally resulted in a decrease in the amount of Cd sorbed. S-curve isotherms were observed for Cd sorption by all soils, suggesting preferential association of Cd with aqueous solution components at low Cd solution concentrations. The removal of soluble organic material by a careful washing procedure resulted in Cd sorption following an L-curve isotherm, indicating that Cd in soils is complexed by aqueous organic ligands whose effect on adsorption is significant at low Cd concentrations (0.08 ..mu..mol kg/sub a//sup -1/).

The role of calcium oxalate in the availability of phosphorus in soils of semiarid regions: a thermodynamic study

Abstract: Evidence is presented for the presence of Ca-oxalate crystals at the soil-hyphae interface of mycorrhizal Pascopyrum smithii. This prompted the development of a thermodynamic model that uses the ability of oxalate to scavenge Ca2+ ion from the soil solution. The model predicts the increased solubility of Ca-apatite when oxalate is present in both the calcite-apatite (calcareous) system and in the exchangeable Ca-apatite (noncalcareous) system. The result is a marked increase of soluble (available) P in solution relative to the situation where oxalate is absent. The model is formulated on conditions prevalent in semiarid soils and presents a possible mechanism by which phosphorus uptake of plants is enhanced by mycorrhizal infection.

Thermal conductivity of two porous media as a function of water content, temperature, and density

Abstract: Appropriate values for the thermal conductivity, which include the contribution of vapor transfer, are required to describe heat transport in a porous medium. We measured the apparent thermal diffusivity of a glass bead medium and a Norfolk sandy loam (Typic Paleudult) as a function of water content

Relationship of Soil Dispersibility to Infiltration and Erosion of Southeastern Soils

Abstract: Fifteen agricultural topsoils from Georgia were subjected to simulated rainfall at high intensity in runoff pan studies. Infiltration over time and total soil loss were not related to soil texture, but were correlated with each other. Both infiltration and soil loss were highly correlated with several measures of soil dispersibility. Dispersible clay measured after 36 h of shaking at an 8:1 water:soil ratio and a dispersible clay index weighting clay dispersion by time were significantly related to both soil loss (r = 0.88 to 0.89) and infiltration (r = -0.5 to -0.6). Dispersion expressions derived from plots of log (undispersed clay) versus time had lower correlation coefficients, as did dispersion variables that included both silt and clay. The high percentage of clay that is dispersible in these soils appears to seal water transmission pores and reduce infiltration, as observed in sodic soils. Therefore, dispersion may be a fundamental soil property to be considered in erosion prediction and control.

Zinc fractions in soils in relation to zinc nutrition of lowland rice

Abstract: Soil zinc fractionation studies revealed that more than 90% of the total zinc occurred in the relatively inactive clay lattice bound form and that a small fraction, viz., 0.26, 0.74, 1.58 and 0.71% of the total occurred as water-soluble and exchangeable, organic complexed, amorphous sesquioxide, and crystalline sesquioxidebound forms. The applied zinc was transformed to the latter four forms following their relative order of preponderance in native soils and constituted on an average 3.68, 12.17, 19.85, and 5.33%, respectively, of the applied amount. Waterlogging caused an increase in the organic complexed and amorphous sesquioxide-bound forms of native soil zinc with a concomitant decrease in the content of the other forms, suggesting the occurrence of a dynamic equilibrium of these forms in soil. Simple correlation and multiple regression analyses showed that the zinc fractionation data obtained from the soils after incubation were more relevant than the same obtained from the cropped soil in predicting zinc concentration of lowland rice plants. The path coefficient analyses revealed that organic complexed zinc played the most important role in zinc nutrition of lowland rice and lent support to the validity of the zinc fractionation scheme suggested by Murthy (1982) and modified by us in this regard.

Effects of polyacrylamide and irrigation method on soil physical properties

Abstract: The objective of this study was to observe the effects of irrigation method and polyacrylamide additions on selected soil physical properties. Polyacrylamide (PAM) was applied to fallow clay loam soil to the rate of 650 kg ha1. The PAM-treated plots were flood-irrigated at the rate of 5 cm w

Effect of Humic Acid on Aluminum Toxicity in Corn Plants

Abstract: We conducted greenhouse experiments to study the effect of humic acid on corn seedlings grown in sand, receiving 0 to 50 mg kg−1 Al and 0 to 350 mg kg−1 humic acid (HA). Fertilization was supplied in the form of a Hoagland-Arnon solution adjusted to pH 4.8. In the absence of HA, increasing amounts of Al in the growth media sharply decreased dry matter production. Total dry weight was reduced from 6.8 g/four plants at 0 Al to 4.0 g/four plants at 50 mg kg−1 Al. Plants treated with 50 units Al developed symptoms of Al toxicity, which appeared as marginal chlorosis and necrosis. The addition of HA to pots containing Al increased dry matter production by 32.5 to 42.5% over those with 0 unit HA, and the plants appeared healthy and green. The beneficial effect of HA was also reflected in the Al and P contents of the corn leaves. Leaf-Al concentrations increased linearly with increased Al treatments at 0 units HA, but decreased from a high of 86.6 μg g−1 at 50 units Al and 0 unit HA to 60.5 and 57.4 μg g−1 with 100 and 350 units HA, respectively. The increase in leaf-Al content as a result of Al stress coincided with a decrease in leaf tissue P contents. However, addition of HA suppressed the reduction in concentrations of leaf P, which accompanied Al stress. At treatments with 50 units Al, plants receiving HA contained more P than those at 0 unit HA. Indications suggested that high amounts of Al in solution reacted with P to form insoluble Al phosphates. However, the presence of HA may have chelated most of the Al, rendering it inactive for reaction with P.

Using A Computed Tomography Miniscanner In Soil Science

Abstract: In a previous paper (Crestana et al. 1985) we demonstrated the possibility of using computed tomographic (CT) scanning for investigations in soil science. One of the main limitations was the complexity and high cost of medical CT scanners. In this paper we report on the characteristics and use of a very inexpensive, homemade CT miniscanner dedicated to soil science analysis. This new apparatus was applied to carrying out tomographies of soil with various water contents and also to obtaining the best conditions and adequate physical parameters for optimized attenuation measurements in soil. Our results demonstrate that it is now possible to have a CT miniscanner, without the limitations of the medical CT scanner, that should be invaluable for advanced studies in soil science.

Polyacrylamide Application in Irrigation Water OT Increase Infiltration

Abstract: Polyacrylamide was tested on furrow-irrigated cotton to assess its ability to improve infiltration on a Holtville silty clay loam (50% clay fraction consisting of 45% montmorillonite). Application was more effective as dilute solution in irrigation water than as dry powder on the soil surfac

Characterization of organic matter from two different soils by pyrolysis-gas chromatography and isoelectric focusing

Abstract: We used the pyrolysis-gas chromatography technique (Py-GC) to characterize mature and immature soil organic matter (PN soil: C/N = 24.8; PS soil: C/N = 12.6). PN produced on pyrolysis an abundance of furfural and phenol, indicating the presence of partially decomposed litter. PS, on the contrary, produced a considerable amount of benzene, which was consistent with a more mature humus. The extracts were fractionated in HAs and FAs and by membrane ultrafiltration, in fractions A1 (mol wt > 105), A2 (>104), and R ( The elaboration of the relative abundances and several Py-GC ratios proved to be very appropriate in assessing differences or similarities among soils and their fractions. Independently of the maturity of soil humus, the A1s and HAs were carbohydrate-rich and composed of highly condensed humus; the Rs were polyphenol-rich, less condensed, and similar to FAs; the A2s showed intermediate properties. IEF has proved a reliable technique for characterizing structurally different organic fractions. The IEF patterns of the fractions were charge-size depenedent, and, on the basis of the charge and heterogeneity, they supported the Py-GC results.

Immediate Effects Of Prescribed Burning On Mineral Soil Nitrogen In Ponderosa Pine Of New Mexico

Abstract: Three 0.1-ha ponderosa pine (Pinus ponderosa Dougl. ex Laws) sites were burned in the fall of 1981. The burn was mainly a ground fire. Burn intensity was 980, 1760, and 2280 kJ s/sup -1/ m/sup -1/ on sites 1, 2, and 3, respectively. We analyzed the mineral soils on each of these sites for total N, NO/sub 2//sup -/ + NO/sub 3//sup -/-N and NH/sub 4//sup +/-N prior to prescribed burning, 1 d postburn, and 30 d postburn. On the most intense burn, NH/sub 4//sup +/-N levels increased threefold from preburn (10 ppm) to 1 d postburn (32 ppm), but declined somewhat 30 d following the burn (24 ppm). Concentrations of NO/sub 2//sup -/ + NO/sub 3//sup -/-N on site 3 rose from 1 ppm preburn and 1 d postburn to 5 ppm 30 d postburn. There were no significant differences in soil total N after burning. Immediate postburn inorganic N values for ponderosa pine mineral soils have not been previously reported in the literature. It is important to investigate burned soils immediately after burning to better understand sequential processes involved in postfire inorganic N dynamics.

Amelioration of soil physical properties by Mucuna after mechanized land clearing of a tropical rain forest

Abstract: The effect of mucuna (Mucuna utilis) cover on the physical properties of an Oxic paleustalf in western Nigeria, previously cleared by four different methods was studied. The methods used were manual clearing and clearing with a shearblade, a tree-pusher, and a treepusher/root rake. The soil physical properties measured were total porosity, penetrometer resistance, infiltration, and soil water retention. In contrast to cropping, mucuna cover improved soil porosity, penetrometer resistance, and hydraulic properties in all treatments. Total porosity of the 0- to 100-mm depth increased with mucuna cover from 0.55 to 0.59, 0.54 to 0.57, and 0.57 to 0.59 m³ m-3 in the manual, shearblade, and treepusher clearing treatments, respectively. Porosity of the treepusher/root rake clearing method was unaffected by mucuna cover. Penetrometer resistance of the 50- to 70-mm depth decreased with mucuna from 426 to 409, 425 to 418, 436 to 398, and 412 to 403 kPa in the manual, shearblade, treepusher and treepusher/root rake methods, respectively. Cumulative infiltration amounts over 3 h of the plots sown to mucuna were 134.1, 55.2, 14.6, and 186.8% greater than the corresponding cropped plots for the manual, shearblade, treepusher, and treepusher/root rake treatments, respectively. Similar decreases were noted in soil water retention at a potential of 0 kPa. The beneficial effects of mucuna cover were greater in manually cleared and tree-pusher-cleared plots. It was indicated that where land clearing causes high soil compaction, mucuna cover for about 1 yr would be a useful practice to restore soil physical properties to favorable levels for arable farming

Competitive interactions of phosphate and molybdate on arsenate adsorption

Abstract: The adsorption of arsenate by a Cecil clay was found to be suppressed by the competitive effects of phosphate and molybdate. The usefulness of two competitive Freundlich-type equations that have been used to model the competitive interactions of dilute organic solutes by activated carbon was examined for application to arsenate adsorption by a Cecil clay as influenced by phosphate and molybdate. The equation of DiGiano et al. had the potential of being able to predict the effects of competition on adsorption based entirely on single-component data. The Sheindorf et al. equation required the collection of competitive data to derive a competitive coefficient. Both expressions were found to be useful, although there was no clear indication of which, if either, was the more accurate. The ability of both expressions to describe the data appeared to be limited to situations where the ratios of the equilibrium concentrations of As/P and As/Mo were greater than 20, i.e., when the equilibrium concentration of As was much greater than that of P or Mo. This limitation was partly attributed to the regression procedure used to calculate competitive coefficients.

Knudsen diffusion: the effect of small pore size and low gas pressure on gaseous transport in soil

Abstract: The analytical principles and applications of the theory of Knudsen diffusion are reviewed, with emphasis on gas transport in the soils of planetary bodies. Knudsen diffusion occurs when the mean free path of diffusing gas molecules surpasses the size of the pores through which diffusion proceeds. The process is then dominated by collisions with the pore walls. Computational techniques for deriving the Knudsen coefficient for soils with a nonreentrant cross-section shape are reviewed, along with methods of deriving a coefficient for soils which permit both Knudsen and bulk diffusion. Sample calculations for three pore-size distributions are provided to illustrate the decrease in transport efficiency with increasingly smaller soil pore sizes.

Empirical Modeling Of Soil Nitrogen Mineralization1

Abstract: The goodness-of-fit of first-order and empirically determined equations to net nitrogen mineralization data obtained by various investigators in laboratory incubations and greenhouse and field experiments is compared. In the majority of instances the empirically determined equation has a lower root-mean-square than does the first-order model. Parabolic functions of the form Y = AXB provided a good fit to most of the data. All the greenhouse and field data were fitted closely by the parabolic model or by a linear model, which can be considered as a special case of the parabolic model where B = 1. The first-order model, based upon the concept of a single pool of mineralizable N of discrete size, does not conform to reality and is inferior to empirically determined models as a means of describing nitrogen mineralization.

A possible source of humic acids in volcanic ash soils in Japan-charred residue of miscanthus sinensis

Abstract: We compared the physicochemical and spectroscopic properties of humic acids obtained from the charred residue of Miscanthus sinensis Anderss and the A horizons of volcanic ash soils in Japan. The elementary composition, Δlog K and RF values, UV, visible, and IR absorption spectra, and x-ray diffraction pattern of the acids are similar to those of the soils. The findings indicate that the charred residue of Miscanthus sinensis deserves attention as a possible source of humic acids with a high degree of darkening in volcanic ash soils in Japan.

Effect Of Polyacrylamide On Seedling Emergence In Crust-forming Soils

Abstract: Polyacrylamide (PAM) in granular and solution form was applied to the surface in the field and glasshouse to test effects on soil crusting nd seedling emergence. Emergence improved when soils were treated with PAM solutions, but not when treated with granular PAM. On soils in different initial physical conditions, liquid PAM kept soil aggregates stable through-out seven irrigation events and reduced penetrometer resistance. PAM applied as granules did not maintain aggregate stability or reduce penetrometer resistance. Neither liquid nor solid PAM created new aggregates, but soil aggregates treated with liquid PAM were preserved in the physical form existing at the time of application. Alfalfa (Medicago sativa L.) emerged days earlier from aggregated soils treated with PAM in solution than from soils treated with granular PAM.