Subsoil Material Research Articles

Transformation rate of 1,3‐dichloropropene and 3‐chloroallyl alcohol in topsoil and subsoil material of flower‐bulb fields

AbstractThe extent of the risk of (Z)‐ and (E)‐1,3‐dichloropropene and their transformation products (Z)‐ and (E)‐3‐chloroallyl alcohol causing a hazard to the quality of groundwater pumped up for public water supply from below flower‐bulb fields has been evaluated. The 1,3‐dichloropropenes were incubated at 10°C in water‐saturated subsoil material from three such fields. A first stage with gradual transformation was followed by a second stage with comparatively rapid transformation and after three months negligible amounts remained. The 3‐chloroallyl alcohols were incubated at 15°C in soils from the root zone of the same fields. Complete transformation had occurred in about a week or even less. The 3‐chloroallyl alcohols were also incubated in the water‐saturated subsoil material at 10°C. Again, a first stage with gradual transformation was followed by a second stage with fast transformation. In most instances, the concentrations had fallen to a very low level within three months. It was concluded that it is unlikely that residues in the upper groundwater would permeate into the deeper groundwater pumped up for public water supply.

NITRATE TRANSPORT ON A SANDY COASTAL PLAIN SOIL UNDERLAIN BY PLINTHITE

ABSTRACT Transport of nitrate (NO3-N) by surface runoff, shallow subsurface flow, and leaching during 1988-89 was determined on a sandy Coastal Plain soil having plinthic subsoil materials. The study was conducted on a small (0.34 ha) instrumented watershed. Nitrate concentrations were measured in surface runoff, shallow subsurface flow, soil samples collected from the upper 30 cm of the root zone, and water samples collected from shallow and deep wells. The study showed that most of the NO3-N leached from the upper 30 cm of the root zone within 1.5 months after N application, given a total rainfall of 200 mm or more. Surface runoff NO3-N concentrations and loads were small, with monthly loads not exceeding 0.3 kg/ha. Nitrate concentrations in shallow groundwater (0.9 to 1.8 m) during the sweet com growing season reflected applied N, with values ranging from 11 to 19 mg/L. Applied N was also reflected in shallow subsurface flow during the spring months. Mean NO3-N concentrations in subsurface flow ranged from 3.9 to 14.1 mg/L, while monthly loads ranged from 0.1 to 9.2 kg/ha. The study indicated that some NO3-N is being lost by vertical water movement in plinthic Coastal Plain soils towards deeper groundwater, and that this loss pathway should be of environmental concem.

Microbial Transformation of 1,2‐Dibromo‐3‐Chloropropane (DBCP)

AbstractA once widely used nematicide that is now banned, 1,2‐dibromo‐3‐chloropropane (DBCP), persists in groundwaters and is a significant pollutant in some water supplies. A study was conducted to determine whether a means for the biodegradation of this persistent compound could be devised. DBCP was not converted to organic products, halide, or CO2 in unamended samples of soil, subsoil material, or groundwaters in 60 d, and no microorganism could be isolated that was able to use the compound as a C source for growth. However, cell suspensions of Pseudomonas putida and of bacteria grown in solutions containing chlorinated fatty acids or 3‐chloro‐1‐propanol cometabolized DBCP in the presence of O2 with the formation of halide but not CO2. Pseudomonas putida had the greatest activity. DBCP was also converted aerobically to organic products and CO2 by soil suspensions incubated with methane. The compound was also converted anaerobically to organic products but not CO2 in suspensions of soil, but no anaerobic transformation was observed in samples of groundwater or aquifer solids. We suggest that biological treatment may be used as a means to destroy this pollutant.

Soil movement by tillage as affected by slope

Exposure of subsoil material on ridge tops and adjacent sideslopes indicates soil movement away from these positions, i.e. soil erosion. A study was conducted on the University of Minnesota Southwestern Experiments Station to determine if soil movement by tillage could be a contributing factors to the apparent soil erosion present on many ridge tops. Numbered soil movement detection units (11-mm steel hexagonal nuts) were buried 10-cm deep in a grid network in 16 individual plots, on a sideslope with slopes ranging from 1 to 8%. Plots were moldboard plowed and disked in June, and again in August. The direction of tillage was either across the sideslope or up- and downslope. The soil movement detection units were then located with a metal detector, excavated and identified, and distance moved was measured in relation to movement perpendicular and parallel to the direction of tillage. Soil movement was directly related to slope. Movement perpendicular off the moldboard on the direction of tillage was greater than movement perpendicular off the moldboard. Calculations on the angle of movement in relation to tillage direction showed movement toward the downslope position. Results from this study suggest that soil movement by tillage can contribute to soil movement off ridge tops and adjacent sideslopes.

Effect of different drainage systems on bearing resistance of some West Coast, South Island soils

Abstract Development of extensive areas of West Coast, South Island wetland soils into pasture has led to unacceptable levels of pugging and loss of pasture production when cattle are introduced following sheep grazing. Since no quantified drainage trials had been carried out previously on the West Coast, a trial was established to test two main drainage systems, subsoiling and “humps and hollows”, with several supplementary treatments including tile drains and gravel-filled slits. The site was on a very gently sloping, weakly dissected, mainly loess-covered glacial outwash terrace in the upper Grey Valley under an annual rainfall of about 2000 mm. Gley podzols (Okarito Series) from loess were the most common soils, with smaller areas of gley soils (Maimai Series) from glacial outwash gravels. Minor areas of organic soils (Kini Series) from peat were significant in the trial area. The site was developed from pakihi vegetation to ryegrass/clover pasture, beginning in 1977. Extensive rush clumps subsequently grew there. The main field measurement made to determine the effect of drainage on bearing capacity was plate-bearing resistance. In addition, water content, dry bulk density, loss on ignition, and thickness of root mat were determined on cores taken near each measurement site. Measurements were made from 1983, before the systems were installed, to 1987. General relationships were found between water content and plate-bearing resistance for each trial plot, and for all sites with Okarito soils. Sites underlain by Kini, Maimai, and Okarito soils with peaty topsoils, had significantly lower plate-bearing resistance compared with Okarito soils with mineral topsoils on major interfluves, regardless of the drainage treatment applied. In the first year after installation, the driest parts of the hollows in the humps and hollows treatment (Okarito subsoil material) had very high bearing resistance. The trial data show that Okarito soils with mineral topsoils will withstand cattle treading without the additional drainage treatments attempted here. Detailed soil survey, with subsequent fencing and management to isolate areas with low bearing resistance, will lead to future higher productivity on such soils.

Pesticide contamination of groundwater in western Europe

In recent years, many measurements have been made of residues of pesticides in shallow and deep groundwater in western Europe. Some triazine herbicides and their transformation products have been detected most frequently. The average concentration in measuring series for deep groundwater was usually below 0.1 μg l −1, and the highest values were usually below 0.5 μg l −1. The concentrations of mecoprop in deep groundwater ranged up to 0.6 μg l −1 and those of bentazone to almost 1.0 μg l −1. Some other herbicides were found at comparatively high concentrations and the highest values were found for TBA and TCA in tile-drain water. The soil fumigant 1,3-dichloropropene was mainly found in shallow groundwater, but its admixture 1,2-dichloropropane was also found in deep groundwater (range up to 10 μg l −1, sometimes even higher). Residues of the nematicides aldicarb and oxamyl have been measured in shallow and intermediate groundwater, but measurements for deep groundwater are still lacking. Some carbamoyl-oximes were incubated in subsoil materials to study their transformation and their rate of transformation in anaerobic subsoils was surprisingly high. The maximum admissible concentration of 0.1 μg l −1 in a Directive of the European Communities of 1980 is the subject of much debate, because a toxicological basis is lacking.

Physical Properties of Constructed and Undisturbed Soils

AbstractThere is a growing impetus to use soil properties to determine if reclamation efforts are adequate to restore productivity. Constructed mine soils were studied 4 and 11 yr after reclamation to determine physical and hydrological properties. Soils constructed using similar methods and with similar vegetation histories were compared to each other and to an equivalent undisturbed soil. Bulk density was greater in the topsoil and subsoil materials of the constructed soils than in the undisturbed A and B soil horizons. Macropore volume (pore radii > 15 µm) was greater in the topsoil and subsoil materials at the 11‐yr site relative to the 4‐yr site but was significantly lower than that in the undisturbed soil. Small pore volume (pore radii from 4.5 to 0.1 µm) in the reclaimed topsoil materials was similar to the undisturbed A horizon soil but was larger in reclaimed subsoil materials than in the undisturbed B horizon. Saturated hydraulic conductivity (Ks) of the reclaimed topsoil was about 25% that of the undisturbed A horizons and the reclaimed subsoil Ks was less than 10% that of the undisturbed B horizon. The reduction in Ks was attributed to the increase in bulk density and disruption of soil structural units and associated interpedal pore spaces during mining and soil construction. No significant differences in Ks were found between constructed minesoils 4 and 11 yr after reclamation. The results of this study show that soil properties may be useful for evaluating reclamation success after soil construction.

Compaction Effects on Erosion of Mine Spoil and Reconstructed Topsoil ext

ABSTRACT STANDARD erosion plots were constructed from shale spoil, topsoil and subsoil material in Western Kentucky to evaluate the effects of stockpiling and placement density on erosion characteristics of reconstructed soil. We measured erosion with a rainfall simulator one year after plot construction and evaluated the effects of soil density on the USLE cover factor. Tests conducted immediately after the soils were removed from the stockpile and again one year later were used to evaluate the effects of timing after reconstruction on the cover factor. The cover factor was between 3.0 to 4.0 for freshly compacted plots constructed from stockpiled materials. One year later, the cover factor had fallen to near 1.5 for compacted materials. The cover factor was near 1.5 for both freshly constructed and one year old compacted shale plots. Subfactors for time after construction and for density are proposed.

Tree uprooting: review of impacts on forest ecology

This paper reviews the ecological effects of tree uprooting. In many forests, disturbance by uprooting is the primary means of maintaining species richness and diversity. Treefall may be due to exogenous factors or it may be endogenously created, although the former predominate. The canopy gap formed by downed trees is often vital to community vegetation dynamics and successional pathways, by providing high light niches (gaps) for pioneer species, by encouraging release of suppressed, shade-tolerant saplings, and through recruitment of new individuals. Nutrient cycling may be affected by uprooting as subsoil materials are brought to the surface, via additions of woody debris to the forest floor, through exposure of bare mineral soil, and by changes in throughfall chemistry. The influence of the resultant pit/mound microtopography on understorey herb distribution is largely due to microclimatic and microtopographic variation. Tree seedling distribution, however, is related to microtopography primarily through differences in soil morphology, nutrition, and moisture content of mound and pit sites.

Surface Runoff and Shallow Ground Water Quality as Affected by Center Pivot Applied Dairy Cattle Wastes

ABSTRACT DAIRY cattle wastes were applied to separate areas by center pivot irrigation at mean N rates of 91 and 44 kg/ha per month. Total N was determined on surface runoff samples from each area. Nitrate contamination of shallow ground water was measured in water samples collected from 23 sites, with each site having piezometers at 1.2, 2.4, and 3.6 m. Total cumulative N loads in surface runoff for June 1982-February 1985 from the high and low wastewater rates were 147 and 47 kg/ha, respectively. Mean monthly NO3 N concentrations of 10-70 mg/L, 10-50 mg/L, and 5-35 mg/L were found in the shallow, intermediate, and deep piezometers, respectively. Significant differences in shallow ground water N03~N concentrations were not found between the two wastewater application rates. Substantial NO3 N contamination at 3.6 m occurred despite dense very slowly permeable plinthic and subsoil materials.

Tracing movements of topsoil by magnetic measurements: two case studies

An array of magnetic measurements is used to trace the occurrence of magnetically enhanced topsoil in two different environmental settings. The first is a cultivated slope section where the results confirm that movements of topsoil have occurred, but that identification of specific erosional processes is problematic. The second is a lake-catchment system where measurements on soils and sediments allow a partial reconstruction of soil movements from different sources over the last 200 y. The study highlights both the need to analyse the magnetic mineralogies of different particle size fractions and the difficulties that may be encountered in trying to discriminate between topsoil and subsoil material on the basis of demagnetization parameters alone.

Accumulation of Airborne Trace Pollutants by Arctic Plants and Soil

Plant and soil samples from 4 locations in Spitsbergen (Norway) were analysed for major ions, heavy metals, polyaromatic hydrocarbons (PAH) and chlorinated pesticides. The results indicate that trace amounts of these substance groups result from a number of different sources, namely from subsoil material, local emissions and long range atmospheric transport. A comparison of inorganic and organic micropollutant concentrations allows a distinction between trace substance uptake from soil or air. The correlation of plant and air concentrations makes it obvious that elevated accumulation rates of heavy metals in plants result from low level transport of particles. PAH are very effectively retained by species with large surface areas and represent particle concentrations in the air. Benzohexachloride in plants results from precipitation water rather than from direct uptake of gaseous traces.

PREDICTING VOLUMETRIC WATER RETENTIONS FOR SUBSOIL MATERIALS FROM COLCHESTER COUNTY, NOVA SCOTIA

Relationships between soil water retention and soil properties were developed for subsoil materials from Colchester County, Nova Scotia. The significant variables in the regression equation for soil water content at a suction of 33 kPa were the sand content and the product of silt content and bulk density of the soil. The variables for water retention at 1500 kPa suction were the clay content and the product of organic matter content and bulk density. The multiple correlation coefficients were 0.87 and 0.92 for suctions of 33 and 1500 kPa, respectively. The developed equations were comparable to ones derived elsewhere. Key words: Water retention, texture, organic matter, bulk density

EFFECT OF PHOSPHORUS LEVEL ON NITRIFICATION RATES IN THREE LOW-PHOSPHORUS ULTISOLS

Using perfusion and batch incubation, we determined minimum levels of inorganic phosphorus (P) required for maximum activity of nitrifying bacteria in soils. Three Pdeficient subsoil materials (Arenic Paleudult, Typic Paleudult, and Aquic Hapludult) were limed to approximately pH 7 and treated with various rates of P as KH2PO4 and Ca(H2PO4)2 to establish comparable P concentrations in perfusates and soil solutions. Ammonium sulfate and KNO2 were used as ammonium and nitrite substrates; an enriched inoculant was added to ensure an equal number of nitrifiers. We monitored nitrite, NO3-, pH, and P 2 d after the initiation of experiments and weekly thereafter. Nitrification at each P level was graphed as a function of time, to determine the effect of P on delay times and maximum nitrification rates. Inorganic P concentrations above which NH4+ oxidizers would not respond to additional P were 0.59 ± 0.24 μM for the minimum delay time and 0.60 ± 0.28 μM for the maximum nitrification rate. Nitrite oxidizers required no more than 0.13 and 0.24 ± 0.07 μM P for the minimum delay time and the maximum oxidation rate, respectively.

Bromide and Phosphate in Runoff Water from Shaped and Cloddy Soil Surfaces

AbstractEffects of soil surface shaping and clods on the release of applied bromide and phosphate to runoff were investigated experimentally with small pervious boxes and simulated rainfall. The soil material used for the surface shaping experiment was a sample of Ruston loam subsoil, < 4 mm in size. Phosphate as Ca (H2PO4)2 · H2O was mixed with the dry soil (0.008% P by weight) before packing in boxes. Triangular ridges, 3.5 cm in width and 1.7 cm in height, were made either along the slope or across the slope of the soil surfaces. Both types of ridges exposed about 12% more surface area than the control soil boxes without ridges. The soil boxes were wetted with a KBr solution (4000 ppm Br) before application of rainfall. Average Br concentration of runoff from a 1‐h, 6.8 cm/h, rainfall in both lengthwise‐ and cross‐ridged boxes was nearly four times that of the control boxes. The ridging also increased dissolved and reactive P concentration of runoff, but only by about 15%. When the upper 2.5 cm of the packed soil consisted of 4‐ to 20‐mm clods, the average Br concentration of runoff was nearly 48 times that of the control, even though the infiltration was 2.5 times more. Increasing the thickness of the surface cloddy layer to 5.0 cm delayed the start of runoff considerably, and yet the Br concentrations of runoff were higher then those with a 2.5‐cm layer of clods. In another soil (Parsons clay subsoil material), having more stable clods than Ruston loam, the Br concentrations of runoff were two orders of magnitude greater than control.

A seismic refraction survey for an expressway project in Singapore

Geophysical methods of site investigation have been used in civil engineering for many years. Of these methods, seismic refraction survey is perhaps the most highly developed. This paper describes such a survey which was carried out for a proposed expressway in Singapore. The proposed 11 km expressway runs through the Bukit Timah Granite Formation. Acid rocks including granite, adamellite and granodiorite together with various hybrids, which were the results of the assimilation of basic rock within the granite, are present in the formation. Because of the local geological formations, the limited accessibility of the site, and the need for speed and economy, seismic refraction survey had been selected for the subsoil investigation. The study aimed to establish the depth of rockhead level, the type of subsoil materials and the foundation conditions for the planning and construction of the expressway and its flyovers and tunnels. Multi-channel equipment was used for the seismic survey. The energy source was explosives. This paper describes the field procedures and the techniques used for interpreting the results. The problems encountered and the limitations of this survey are discussed. In addition, the findings of the seismic survey are compared with the logs from the boreholes sunk into the bedrock along the expressway alignment. Generally, the results of the seismic survey were found to be satisfactory.

Reinforced earth structures situated on soft foundations

The authors investigate weaknesses in some current empirical design studies when used with structures situated on poor ground. Although it is theoretically possible to show that conventional earth retaining structures should be better suited to sites with poor bearing pressure capacity than reinforced earth structures, this is not generally the case in practical experience. A series of parametric studies using common material properties and an embankment height of 9 M have been undertaken using the program felsta to illustrate the properties of soft and very soft foundations. The effect of the width of the embankment or reinforced earth structure on overall stability is also investigated. It is concluded that the resistance to movement of the reinforced earth structure produced by the subsoil material radically alters the assumption that the structure will rotate forward about the toe. An expression for the stability of the structure is determined. Empirical design rules are only acceptable for narrow embankments. (TRRL)

Topsoil and Subsoil Potassium Calibration with Leaf Potassium for Fertility Rating1

AbstractPlants obtain K from both topsoil and subsoil, but soil testing is usually performed on surface soil. Interpretation of subsoil tests for available K has also been limited by insufficient calibration of subsoil K level with plant growth response. Leaf K response was used to calibrate topsoil and subsoil K levels for fertility rating.A 4‐year corn (Zea mays L.) — soybean (Glycine max L.) rotation on Marlboro loamy sand (Typic Paleudult) using various rates of K showed a buildup of K in the top 4 cm of B2 horizon with moderate annual K fertilization, but little change in Ap horizon K. Leaf K contents were sufficient where soil tests showed low topsoil and medium subsoil K. No yield response to K was obtained even after 4 years without K fertilization.A 1‐year corn experiment on Orangeburg sand and Faceville loamy sand (Typic Paleudults) using various rates of K showed increased K in both Ap and subsurface horizons 50 and 70 days after K application. No yield response to K additions was obtained on either soil, even though the Orangeburg Ap horizon tested low in available K. The lack of yield response at low K ratings suggested a need for adjustment in the rating.A 3‐year survey of the relationships among corn and soybean leaf K, and available K in Ap and top 10 cm of B2 horizons was made in the Middle Coastal Plain. Most of the soils were Typic Paleudults except for eight Psammentic Paleudults. A range of K application rates was not used at each site, preventing examination of relative yield response to soil K. Correlations were found between leaf K in both corn and soybeans and K in Ap and B2 horizons. To examine the contribution of K from each horizon, soil test calibration was achieved by multiple linear regression of leaf K on Ap and B2 available K values. Soil K fertility ratings were established from the regression equation using values for critical and sufficient leaf K to mark low and high soil test values.This work indicated that soybeans may obtain K from B2 horizons at greater depths than corn and that available K in the B2 horizon should be considered along with Ap soil test K to characterize the soil fertility status, particularly in cases where coarse‐textured topsoils occur over finer‐textured subsoil material.

Particle Size Analysis by Hydrometer: A Simplified Method for Routine Textural Analysis and a Sensitivity Test of Measurement Parameters

AbstractA simple modification of the Day (1965) hydrometer method is suggested for routine textural analysis. The simplified method requires no calibration, graphs or tables and uses a weighted average of the 1.5‐hour and 24‐hour readings to determine the 2µm clay fraction. The relationship is: urn:x-wiley:03615995:saj2sssaj197903615995004300050038x:equation:saj2sssaj197903615995004300050038x-math-0001 whereP2µm = summation percentage for the 2µm clay fraction.P24, P1.5 = summation percentage for settling time of 24 hour and 1.5 hour, respectively.K = weighting factor, used to approximate the actual relation of the summation percentage curve over the clay percentage range of interest.This equation was found to be satisfactory in the range of 5% ⩽ P2µm ⩽60% by weight for over 70 North Dakota soil and subsoil materials when K=0.876.Sensitivity analyses were performed for the Day, Bouyoucos, and the Simplified Day hydrometer methods to determine which of several measured parameters contribute to the greatest possible error; hence which parameters should be controlled with the greatest precision. The hydrometer scale reading error contributes more error than any other single parameter.

Factors affecting the availability to radishes of cadmium added to soil

In a five week period, the cadmium uptake of radishes in pot experiments made in the greenhouse was on average 7.8 % of the cadmium mixed with the soil (0.4 mg Cd per 400 ml of soil). In a material consisting of samples from 25 plough layers the uptake varied from 1.4 to 11 % and in a material of samples from the corresponding subsoils from 14 to 22.6 %. The increase in cadmium content (∆ c) of the radish tops, which increase was regarded here as describing best the availability of added cadmium, varied in the plough layer material from 2.2 to 27.1 mg/kg and in the subsoil material from 4.3 to 94.9 mg/kg Cd on a dry matter basis. The increment ∆ c was related to the amount of organic carbon (x1) and to proportion of hydrogen (x2)) of total exchangeable cations according to the equation ∆ c = k * x2 *b2 /x1*b1. In this equation 0