Top Few Centimeters Of Soil Research Articles

An innovative strategy for control of the chestnut weevil Curculio elephas (Coleoptera: Curculionidae) using Metarhizium brunneum

The chestnut weevil (Curculio elephas) is a major pest of chestnut. Female weevils oviposit in the fruit and emergent larvae eat the kernel, making the nut unmarketable. In Turkey, the fruit is gathered into piles called gomu and allowed to ripen over a 1–2 month period. Late instars emerge from infested nuts to pupate in the soil underlying the gomu. Since the pest is concentrated, the opportunity exists for targeted control with biological control agents such as entomopathogenic fungi (EPF) and nematodes (EPN). The efficacy of the EPF Metarhizium brunneum strains ARSEF 4556 and V275 used alone and in combination with the EPN Heterorhabditis bacteriophora on the mortality of last instar chestnut weevil was assessed. Both M. brunneum ARSEF 4556 and V275 were highly virulent causing 86% and 94% mortality, respectively. Although H. bacteriophora killed the larvae (68% mortality) more quickly, the fungal strains were more efficacious 12 days post-inoculation. Application of ARSEF 4556 and V275 as a top dressing (spreading the fungus uniformly over the soil surface) in simulated gomu resulted in 78% and 80% larval mortality in laboratory pot tests and 83% and 70% mortality in outdoor trials, respectively. Premix applications (mixing the fungus in the top few centimeters of soil) of ARSEF 4556 and V275 resulted in 83% and 85% larval mortality indoors, respectively, yet outdoor trials caused >80% larval mortality. These EPF strains were also evaluated against larvae of the chestnut tortrix, Cydia splendana, which also feeds on nut kernels, and emerges at the same time as the chestnut weevil larvae to pupate in the soil. Both ARSEF and V275 caused 96.6% mortality inlast instar C. splendana. In contrast, the most virulent EPN (Steinernema feltiae) caused only 80% mortality. Co-application of this nematode with M. brunneum resulted in 100% mortality with the interactions being additive.

Spatial Distribution and Temporal Variability of Arsenic in Irrigated Rice Fields in Bangladesh. 2. Paddy Soil

Arsenic-rich groundwater from shallow tube wells is widely used for the irrigation of boro rice in Bangladesh and West Bengal. In the long term this may lead to the accumulation of As in paddy soils and potentially have adverse effects on rice yield and quality. In the companion article in this issue, we have shown that As input into paddy fields with irrigation water is laterally heterogeneous. To assess the potential for As accumulation in soil, we investigated the lateral and vertical distribution of As in rice field soils near Sreenagar (Munshiganj, Bangladesh) and its changes over a 1 year cycle of irrigation and monsoon flooding. At the study site, 18 paddy fields are irrigated with water from a shallow tube well containing 397 +/- 7 microg L(-1) As. The analysis of soil samples collected before irrigation in December 2004 showed that soil As concentrations in paddy fields did not depend on the length of the irrigation channel between well and field inlet. Within individual fields, however, soil As contents decreased with increasing distance to the water inlet, leading to highly variable topsoil As contents (11-35 mg kg(-1), 0-10 cm). Soil As contents after irrigation (May 2005) showed that most As input occurred close to the water inlet and that most As was retained in the top few centimeters of soil. After monsoon flooding (December 2005), topsoil As contents were again close to levels measured before irrigation. Thus, As input during irrigation was at least partly counteracted by As mobilization during monsoon flooding. However, the persisting lateral As distribution suggests net arsenic accumulation over the past 15 years. More pronounced As accumulation may occur in regions with several rice crops per year, less intense monsoon flooding, or different irrigation schemes. The high lateral and vertical heterogeneity of soil As contents must be taken into account in future studies related to As accumulation in paddy soils and potential As transfer into rice.

Declining soil quality in South Africa: effects of land use on soil organic matter and surface crusting

Soil conservation in South Africa has historically focussed on preventing soil erosion. Effective maintenance of the soil resource requires, in addition to erosion control, an understanding of how land use practices affect more subtle indicators of soil quality. This review outlines how land use in South Africa can rapidly result in a marked reduction in soil organic matter (SOM) content and a greater tendency of soils to crust. Removal of a cover of vegetation whether by ploughing, grazing or burning tends to reduce SOM due to reduced organic matter inputs and enhanced soil microbe activity. Loss of SOM, particularly from the top few centimetres of soil (named here the pedoderm) has a disproportionately large effect on soil infiltrability and nutrient supply. The mineralogy of the clay fraction also has great bearing on the response of soil to land use effects. The unexpected role of quartz in soil dispersion and crusting in South Africa has only recently been unveiled. Apart from SOM effects, land use can lead to subtle changes in soil chemistry. Plantation forestry has resulted in an increase in soil nitrate in many areas, possibly due to greater mineralisation under forests than grasslands. Annual burning in the Kruger National Park bushveld has been shown to increase clay dispersibility and crusting of the pedoderm, which was ascribed to a reduction in electrical conductivity and SOM as well as an increase in the exchangeable sodium percentage. Soil quality is a multifaceted concept. One aspect stands out, however, as critical and that is the conservation and replenishment of nitrogen which is all important for retaining humus and maintaining soil quality.

Frequent fires intensify soil crusting: physicochemical feedback in the pedoderm of long-term burn experiments in South Africa

Savannas and grasslands in South Africa are adapted to fire, yet long-term effects of fire on soil, water and nutrients remain largely unknown. To determine whether frequent burning increases the tendency of soils to crust and alters soil chemistry, topsoils from 19 sites were examined in Mpumalanga, KwaZulu-Natal and the Eastern Cape where annual burning and fire exclusion experiments had been conducted for at least 28 years. A comparison of soils from burnt and unburnt plots revealed that composite samples taken to a depth of 10 cm from burnt plots had lower laboratory infiltration, electrical conductivity (EC) of 1:5 extracts, water-soluble K, water-soluble NH 4, total C, total N and labile C. Burnt plots had higher pH in KCl, water dispersible clay and modulus of rupture. Rate of soil respiration from composite samples (0–2 cm) from burnt plots was lower than from unburnt plots (means of 21 vs. 36 ng C g −1 s −1). Rainfall simulation on the same samples demonstrated that burnt plots crusted more rapidly than unburnt plots (19 vs. 35 mm h −1), while results from sampling at 1-cm intervals revealed that the greatest differences between burnt and unburnt plots were in the 0–1 cm layer. The top few centimetres of soil are likely to have a disproportionate effect on ecosystem functioning by influencing the rate of infiltration and mineralisation of soil organic matter. This thin surface layer has been named the pedoderm in this paper. Soil from 0–1 cm in burnt plots had lower total C (means of 0.8% vs. 2.7% for burnt and unburnt plots, respectively), total N (0.07% vs. 0.23%), (NH 4)OAc-extractable Ca (7 vs. 17 mmol c kg −1), Mg (2 vs. 7 mmol c kg −1), K (0.8 vs. 1.5 mmol c kg −1) and a greater exchangeable Na percentage (17% vs. 8%). The results indicate that burning increases soil crusting. This was ascribed to a decrease in humus content (and associated disaggregating effect) and an increase in the dispersion of clay. Nutrients are lost from burnt plots over time, probably by the removal of ash in surface runoff. Calcium, Mg, and K were lost more readily than Na probably because plants take up these nutrients in greater concentration than Na. The net effect was an increase in the exchangeable sodium percentage (ESP). Crusting on burnt plots may be self-perpetuating, because increased runoff is likely to increase the loss of soluble salts.

Exploring for deeply covered mineral deposits: Formation of geochemical anomalies in northern Chile by earthquake-induced surface flooding of mineralized groundwaters

Research Article| November 01, 2002 Exploring for deeply covered mineral deposits: Formation of geochemical anomalies in northern Chile by earthquake-induced surface flooding of mineralized groundwaters Eion M. Cameron; Eion M. Cameron 1Eion Cameron Geochemical Inc., Carp, Ontario KOA 1L0, Canada Search for other works by this author on: GSW Google Scholar Matthew I. Leybourne; Matthew I. Leybourne 2Department of Geosciences, University of Texas, Richardson, Texas 75083-0688, USA Search for other works by this author on: GSW Google Scholar David L. Kelley David L. Kelley 3WMC International, Englewood, Colorado 80012, USA Search for other works by this author on: GSW Google Scholar Geology (2002) 30 (11): 1007–1010. https://doi.org/10.1130/0091-7613(2002)030<1007:EFDCMD>2.0.CO;2 Article history received: 20 May 2002 rev-recd: 25 Jul 2002 accepted: 26 Jul 2002 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Eion M. Cameron, Matthew I. Leybourne, David L. Kelley; Exploring for deeply covered mineral deposits: Formation of geochemical anomalies in northern Chile by earthquake-induced surface flooding of mineralized groundwaters. Geology 2002;; 30 (11): 1007–1010. doi: https://doi.org/10.1130/0091-7613(2002)030<1007:EFDCMD>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Northern Chile is a major producer of copper from porphyry deposits. Most ores worked to date were exposed near the surface. Exploration is now focused on deposits along a basement unconformity buried under piedmont gravels deposited by ca. 10 Ma. Two recent discoveries, the Spence and Gaby Sur deposits, are covered by gravel. Soils above these deposits have anomalies for elements present in saline, mineralized groundwaters. The anomalies occur above fracture zones in the gravels, believed to represent the upward propagation of basement faults that guided emplacement of the porphyries. We propose that during earthquakes in this seismically active region there was pumping of saline basement waters up the faults and fracture zones, entraining mineralized groundwaters from the deposits. After surface flooding and evaporation, elements were redistributed by infrequent rains. Sampling shows that surface-active cations, such as Cu2+, were adsorbed and retained in the top few centimeters of soil, whereas NaCl and porphyry indicator elements that dissolve as anions (Se, Re, and As) are not adsorbed and are removed to >40 cm depth. Given the 10 m.y. interval since the gravels were deposited, and the hyperarid climate of the Atacama Desert, anomalies may have formed by repeated episodes of seismically induced flooding. Company geochemical surveys show that such features are numerous in northern Chile, producing linear zones of saline soils plus other constituents of local groundwaters (e.g., B and I). Where faults controlling these features intersect mineralization, elements specific to the mineralization are also present. Saline zones may be outlined in the field by measuring the conductivity of soil plus water slurries; sampling for full geochemical analyses can be limited to areas so defined. Anomalies may be generated along fault lines in other seismically active, wetter climates, but only for elements that are adsorbed on soil minerals. Although the context of the study is mineral exploration, the process may be relevant to the formation of geochemical features of environmental interest above major faults. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Distribution patterns of lead accumulation in roadside soils: a case study from Erzurum, Turkey

Surface soils along roadsides or near to industrial areas may contain high concentrations of lead that adversely affect plant production. Lead contamination of roadside soils is generally attributed to the exhaust emissions of automobiles operating with leaded gasoline. The objectives of this study were to determine the relationships between lead accumulation in soils and the distance from the road edge, predominant wind direction and soil depth, and to define vertical and horizontal distribution patterns of lead accumulation within the study area. The lead content of soil decreased rapidly with the distance from the road, and the relationship was described by a power function. The contamination was more dependent on the predominant wind direction. Our results indicated that lead that had accumulated within the top few centimetres of soil had been mixed throughout the ploughing layer in cultivated lands. Soils within 40 m of the motorway had at least 2 to 6 times higher amounts of lead than the background level.

Mass movement of mancos shale crust near caineville, utah: a 30‐year record

Rates of soil creep were studied periodically over a 30‐year period in southeastern Utah on Mancos Shale badland slopes averaging 35 degrees. More intensive studies were carried out over a 10‐year period on slopes averaging 40 degrees. On the 35 degree slope the average rate of movement was 2.71 cm yr−1.On the 40 degree slopes, rates varied from 3.14 to 5.94 cm yr−1.Individual rates of movement varied widely, but average movement of a given line was consistent. No statistical differences in rates of movement were found between north‐ and south‐facing slopes.About two‐thirds of the total movement occurred during the winter/spring period; episodes of rapid movement coincided with years in which storms deposited at least 0.6 cm of precipitation per day for at least two consecutive days. Downslope rotation of nails indicates that creep involves only the top few centimeters of soil.

Transient Diffusion, Adsorption, and Emission of Volatile Organic Vapors in Soils with Fluctuating Low Water Contents

AbstractLaboratory experiments were conducted on large packed soil columns (15 cm diam., 40 cm length) under unsaturated conditions. Trichloroethene (TCE) was introduced at the bottom of the columns. The emissions of TCE from the soil surface were monitored. The soil‐water content at the soil surface was changed by alternating dry and water‐saturated air sweeping over the column surface, thus changing the vapor sorption capacity of the soil. The retardation of VOC gas transport, due to the change in adsorption capacity with change in soil‐water content, was determined by sampling the soil‐air and the sweep air flushing the column headspace. Soil‐water content was monitored by the time‐domain reflectometry (TDR) technique. The transport of VOC gases from experiment initiation until steady‐state was simulated using a numerical simulation model, in which diffusion and equilibrium partition theory were incorporated. Measured and simulated concentration profiles as well as volatilization fluxes agreed very well. The decrease in soil‐water content, caused by sweeping dry air over the column surface, resulted in an increase in the soil adsorption capacity up to several orders of magnitude (mainly in the top few centimeters of soil). Both increase and decrease in soil‐water content affected the volatilization flux manifested in large rapid peaks of TCE volatilizing from the surface. This behavior was likewise simulated using a numerical model with changing diffusion coefficients and retardation factors as function of soil‐air content, and good agreement was obtained between model simulations and measured data.

Phytoremediation of soil contaminated with low concentrations of radionuclides

Ecosystems throughout the world have been contaminated with radionuclides by above-ground nuclear testing, nuclear reactor accidents and nuclear power generation. Radioisotopes characteristic of nuclear fission, such as 137Cs and 90Sr, that are released into the environment can become more concentrated as they move up the food chain often becoming human health hazards. Natural environmental processes will redistribute long lived radionuclides that are released into the environment among soil, plants and wildlife. Numerous studies have shown that 137 Cs and 90Sr are not removed from the top 0.4 meters of soil even under high rainfall, and migration rate from the top few centimeters of soil is slow. The top 0.4 meters of the soil is where plant roots actively accumulate elements. Since plants are known to take up and accumulate 137 Cs and 90Sr removal of these radionuclides from contaminated soils by plants could provide a reliable and economical method of remediation. One approach is to use fast growing plants inoculated with mycorrhizal fungi combined with soil organic amendments to maximize the plant accumulation and removal of radionuclides from contaminated soils, followed by harvest of above-ground portion of the plants. High temperature combustion would be used to oxidize plant material concentrating 137 Cs and 90Sr, in ash for disposal. When areas of land have been contaminated with radionuclides are large, using energy intensive engineering solutions to remediate huge volumes of soil is not feasible or economical. Plants are proposed as a viable and cost effective method to remove radionuclides from the soils that have been contaminated by nuclear testing and nuclear reactor accidents.

Study of underground Adoretus versutus Har. (Col., Scarabaeidae) populations in Vanuatu: detection of cohabitation with other white grubs

AbstractIn the absence of any natural enemies, Adoretus versutus has become the biggest threat to cocoa plantations in Vanuatu since its accidental introduction. Its biological cycle, from the egg stage to adult emergence, takes place in the top few centimetres of soil, preferably in pastures and near the host plants on which the adults feed. Various samples taken for a study of larva population dynamics revealed that five types of white grubs were likely to cohabit. Their existence and identification have to be taken into account before any attempt is made at biological control of A. versutus.

Virus movement in soil columns flooded with secondary sewage effluent

Secondary sewage effluent containing about 3 X 10(4) plaque-forming units of polio virus type 1 (LSc) per ml was passed through columns 250 cm in length packed with calcareous sand from an area in the Salt River bed used for ground-water recharge of secondary sewage effluent. Viruses were not detected in 1-ml samples extracted from the columns below the 160-cm level. However, viruses were detected in 5 of 43 100-ml samples of the column drainage water. Most of the viruses were adsorbed in the top 5 cm of soil. Virus removal was not affected by the infiltration rate, which varied between 15 and 55 cm/day. Flooding a column continuosly for 27 days with the sewage water virus mixture did not saturate the top few centimeters of soil with viruses and did not seem to affect virus movement. Flooding with deionized water caused virus desorption from the soil and increased their movement through the columns. Adding CaCl2 to the deionized water prevented most of the virus desorption. Adding a pulse of deionized water followed by sewage water started a virus front moving through the columns, but the viruses were readsorbed and none was detected in outflow samples. Drying the soil for 1 day between applying the virus and flooding with deionized water greatly reduced desorption, and drying for 5 days prevented desorption. Large reductions (99.99% or more) of virus would be expected after passage of secondary sewage effluent through 250 cm of the calcareous sand similar to that used in our laboratory columns unless heavy rains fell within 1 day after the application of sewage stopped. Such virus movement could be minimized by the proper management of flooding and drying cycles.

Timing of ground truth acquisition during remote assessment of soil-water content

Remote sensing of soil-water content is, at present, limited to the top few centimeters of soil. During a diurnal cycle the near-surface water content undergoes rather wide diurnal fluctuations. Data from five experiments on Avondale loam at Phoenix, Arizona, at various times of the year demonstrated that soil samples taken between 1100 and 1200 hours (MST) best represented the 24 hour average soil-water content. Also, the average of the daily maximum and minimum water contents closely approximated the 24 hour average. The data showed that time of sampling was an important criterion when obtaining ground truth in remote sensing of soil-water content.