Sandy Clay Research Articles

ANALISIS PENYELIDIKAN KARAKTERISTIK TANAH KOTA DENPASAR MENGGUNAKAN METODE BOR TANGAN, DAN UJI LABORATORIUM

ANALISIS PENYELIDIKAN KARAKTERISTIK TANAH KOTA DENPASAR MENGGUNAKAN METODE BOR TANGAN, DAN UJI LABORATORIUM

Erodibility Indices and Soil Loss from Different Land uses in Owukpa and Okaba Bioregion of Lower Coal Measures Geological Sediments of the Anambra Basin, Nigeria

The study on erodibility indices and soil loss from different land uses in Owukpa and Okaba bioregion of lower coal measures geological sediments of the Anambra Basin, Nigeria was conducted forested, cultivated and residential lands. Thirty-nine (39) representative soil samples were collected at a depth of 0 – 20 cm using auger, labeled and preserved to the laboratory for standard laboratory procedures. The percentage of different grain sizes Moisture content, organic carbon, organic matter content, soil pH, bulk density, particle density, porosity, soil structural index, specific gravity, particle size and permeability were verified. The three land uses were predominantly sandy soil and classified as sandy loam, moderate Permeability, low moisture and clay contents. Dispersion, Erosion, Clay and Modified Clay ratios where high, while Water Stable Aggregates was low. Cultivated land use has the highest value of erodibility factor K (0.12) and predicted soil loss was 18.22 tons/ha/yr. Residential land use value of erodibility factor K was 0.10 and the predicted soil loss of 14.80 Tons/ha /yr while forested land use K was lowest (0.08) with predicted soil loss of 11.84 tons/ha/yr. Using one way ANOVA at p ? 0.05 the different land use patterns did not significantly influence erodibility factor and soil loss in the study area.

Temperature‐humidity‐density dependent evaporation behaviour of clay and sandy clay

AbstractTo compare the disparities between free water evaporation and soil water evaporation, and unveil the temporal impact of soil water evaporation in diverse environments, a series of experiments were conducted to observe the soil water content in different temperature and humidity environments. Meanwhile, the soil water characteristic curve (SWCC) and the evaporation process of free water in air were determined, and the sensitivities of temperature, humidity and density on the soil water evaporation process were analysed. The results demonstrated that both external temperature and humidity can serve as variables for controlling the evaporation rate of soil water. These factors exerted a dynamic influence on the evaporation process, with the impact of each factor tending to stabilize as soil water content decreased. The evaporation rate of soil water was higher than that of free water at the initial stage and was lower than that of free water after the soil reached the residual water content; soil water tended to exist in a state with higher entropy than that of free water. This study provides valuable insights for the establishment of a soil water evaporation model.

Response of Olive Trees (Olea europaea L.) cv. Zaity to Bio health and Foliar Spray of Tecamin max and Boron

During the growing season of 2022, the experiment was conducted in one of the private orchards located in Hassan ava village, Zakho district, Dohuk governorate, Kurdistan region, Iraq, to study the response of olive tree (Olea europaea L.) cv. Zaity to biofertilizer (bio health) and foliar spray of the amino acid (tecamin max) and Boron. Olive trees were planted 6 x 6 m apart on clay sandy loam soil and fed with well water using a drip irrigation system. Olive trees were treated with three levels of biofertilizer (bio health) at (0, 1,0 and 15 g.L-1), added to the soil, and three levels of the foliar spray with amino acid (tecamin max) at (0, 10, 15 ml.L-1), and three levels (0, 200 and 300 mg. L-1) of boron foliar spray. A factorial experiment with three replications was carried out in a randomized complete block design (RCBD), using one tree for each experimental unit. The study reached the following results: application of biofertilizer (bio health) in the soil, especially at 15 g.L-1, and foliar spraying of the amino acid (tecamin max) at 15 ml.L-1 led to a significant increase in all studied characters (leaves mineral content N, P, K, and B%) and physical characters of fruit (fruit weight, fruit length, fruit width and total yield per tree) except pulp: stone ratio, while the control treatment gave the lowest average for the aforementioned traits. Foliar spray of boron especially the level of 300 mg. L-1, led to a significant increase in all the studied characteristics (leaves mineral content N, K, and B%) and physical characters of fruit (fruit weight, fruit length, fruit width, and total yield per tree) except pulp: stone ratio and phosphorus content in leaves, while the comparison treatment gave the lowest average for the aforementioned traits. There was also a significant increase in the binary and triple interactions of the study treatments on all the studied traits, especially the high levels of the study factors (15 g.L-1 bio-health, 15 ml.L-1 tecamin max, and 300 mg. L-1 boron).

Late‐Holocene counterpoint deposition in the Lower Rhine River

ABSTRACTChannel deposits from meandering rivers have proven to be far more complex than the well‐known lithofacies model consisting of coarse‐grained channel, gravelly channel‐lag and fine‐grained overbank deposits. Sharp bends in rivers are subject to different hydraulic processes than bends with lower curvatures, enabling erosion of inner banks and deposition of fine‐grained sediments in the outer bend, resulting in downstream migration of river bends. This phenomenon is known as counterpoint deposition, forming counterpoint bars. This research investigates whether scroll bars associated with a sharp bend in the Lower Rhine River, The Netherlands, are such a counterpoint‐bar deposit. A counterpoint bar is expected based on: (i) the surface morphology of the scroll bar; (ii) the confinement of the river course by an ice‐pushed ridge resulting in a sharp bend; and (iii) the archaeological context of successive Roman settlements atop the ice‐pushed ridge, potentially moving downstream with the migrating river bend. This hypothesis is tested through detailed borehole descriptions combined with optically stimulated luminescence dating, the latter being a novel approach to identifying counterpoint deposits. The deposits consist of clays and sandy clays with fine sand laminations, and sporadic larger sand bodies. Further upstream these deposits grade into channel deposits dominated by coarser sands with gravels. These lithologies are explained using earlier proposed mechanisms for counterpoint formation; substrata match those described in previously studied counterpoint deposits and their point bar counterparts. Optically stimulated luminescence dates indicate that the Lower Rhine River bend migrated downstream, confirming counterpoint deposition. A migration rate of 1.93 m/year was established through weighted linear regression. This study demonstrates the potential of optically stimulated luminescence dating to investigate counterpoint bar presence. The identified counterpoint bars and associated bend migration provide insight into meandering river dynamics that is crucial for river management and in aiding river restoration and rewilding initiatives.

Identification Of Soil Resistivity Distribution In Ekoriparian Leuwi Padjadjaran Area Using 2D Electrical Resistivity Method

Research focused on the identification of soil resistivity distribution at the Ekoriparian Leuwi Padjadjaran area, University of Padjadjaran, Jatinangor, has been conducted using geoelectric resistivity method 2D with dipole - dipole configuration. Three survey lines were measured with the first and second lines being 2 meters long and the third line measuring 6 meters. Electrode spacing was set at 0.2 meters, with 10 electrodes on the first and second lines, and 30 electrodes on the third line. Data processing is done using the Res2Dinv software. The research results indicated that resistivity values in the range of 4.00 Ωm to 20.0 Ωm were interpreted as clay rocks, values from 20 Ωm to 200 Ωm were interpreted as silt rocks, and resistivity values in the range of 256 Ωm to 1024 Ωm were interpreted as sandy clay rocks. Based on the geology of the study area, the soil is a fine-grained soil, namely silt and sandy loam.

Geophysical and Geotechnical Investigations of the Subsurface for Construction Purposes at Federal College of Education Osiele, Abeokuta, Southwestern Nigeria

Knowledge of the surface and subsurface structures are vital for construction procedures. Integrated geophysical and geotechnical methods were applied to image the subsurface for evaluation of the stratigraphy and the competency of each geoelectric layer for construction purposes at the Federal College of Education Osiele, Abeokuta South-western Nigeria. Nine Vertical Electrical Sounding (VES) using Schlumberger electrode configurations were conducted over a current electrode spacing of 200 m. Multi-channel Analysis Surface Wave (MASW) was the seismic technique used for the geotechnical analysis of the study area and laboratory analysis was performed to investigate, Atterberg limit, particle size distribution, compaction test, specific gravity, and California bearing ratio. Results from the geophysical investigation revealed four to five geoelectric layers: topsoil, clayey sand, sandy clay, laterite, and fresh basement. The MASW results have s-wave velocities range of 40–500 m/s and analysis showed four layers. The laboratory analysis revealed that all the ten traverses have specific gravity, which is out of limit except sample 8 which is 2.80, plastic index and Atterberg limits of liquid were within permissible values of 12% and 35% respectively except samples 9 and 10, and California Bearing Ratio within specified limits. Geophysical and geotechnical investigation of the subsurface carried out in the study area for construction purposes revealed that the foundation of a heavy structure should be targeted at around 20 m into the subsurface.

Groundwater Potential Evaluation and Aquifer Characterization using Direct Current Resistivity Method in Wasinmi South-West Nigeria

The effectiveness in near-surface characterization makes geoelectrical resistivity techniques viable for groundwater exploration, geotechnical studies and environmental investigations. Geo-electric soundings were carried out in 25 different locations in Wasinmi, South-West Nigeria to acquire aquifer properties required for groundwater production of the study area using Direct Current Resistivity (DCRE) of Vertical Electrical Sounding (VES) utilizing AGI Super-sting Earth Resistivity meter with schlumberger configuration; current electrode spacing (AB) ranging from 1 to maximum of 100 m and the potential electrodes (MN) were consequently changed from 0.25 m to 5 m respectively. The simulated results of the 25 VES points reveal the presence of 3 to 4 geo-electric layers. The top layer comprises clay, sand, siltstone intercalations. Layers underneath the top soil are the Lithified Laterite, Clayey Sand, Clay/Shale, Sandy Clay and Limestone/Sandstone, Saturated, Sandstone Aquifer. The area is also characterized with relatively high depth to sandstone aquifer which varies from 20 m to 69.1 m. This can be attributed to the thick water saturated Shale/Clay and Clayey Sand in the area. However, at the extreme of North-Western part of the study area, depths to aquifer are far lower, with VES location VESWAS15 having a thickness of about 14.4 m. Aquifer thickness in the study area varied from 14.4m to 63.5m. VESWAS19 has the highest aquifer resistivity value (2473 Ωm) in the study area, with depth to aquifer of 69.1 m. The transmissivity varies between 0.17695×/s in VESWAS4 to 8.97654×/s in VESWAS13. This study further shows that aquifer resistivity values vary from 284 Ωm to 2473 Ωm with a range of 2189 with the resistivity values suggesting lithology in the suite of Sandy Clay, Sandstone and Karst Limestone found to be widespread in the study area with mean aquifer thickness value of 32.25 m and a variance of 124.63 m...

Lithological and Structural Factors Affecting Groundwater Occurrence in Eruwa, South West Nigeria

The subsurface Lithological and Structural framework was investigated to understand its effects on groundwater aquiferous occurrence in this study, underlined by the Precambrian Basement Complex of Nigeria, with granite, gneiss, and schist occurring as the dominant rock types. To successfully map the subsurface, fifty-two (52) Vertical Electrical Sounding points were probed to a depth of current electrode spacing of 100m depth to obtain the variation in the resistivity measurement of the underlying weathered basement and basement rock in the subsurface. Apparent resistivity values and current electrode spacing are plotted on a bi-logarithm plot and correlated to standard curves to estimate subsurface layers' depth, thickness, and resistivity values. WinResist software uses a mathematical algorithm to estimate further the geoelectric parameters to find the best-fit model that matches the observed data. Golden Surfer software was used to represent the geoelectric parameters to aid in geospatial representation. Results show 3-5 lithological layers, which include Topsoil, Clay, Laterite, Sand, Sandy Clay, and Fresh Basement with resistivity value range 82.1Ωm - 2648.2Ωm, 21.8Ωm - 98.4Ωm, 102.3Ωm -167.5Ωm, 404.6Ωm - 2468.2Ωm and 606.8Ωm - 20,535.90Ωm indicating a weathered and fresh unweathered basement rocks layers with H, KH, HA, HKH, KHKH, QH and A geophysical curve which are also typical geometry of weathered material and limited or no fractures basement rock layer. Basement rock resistivity, Overburden thickness, Reflection coefficient, longitudinal conductance, Anisotropy coefficient range (606.8Ωm-20535.9Ωm, 2.6m - 35.6m, 0.3-1.0, 0.01-0.86 and 0.7-3.3) respectively which a typical value of shallow to deep overburden layer with limited or no-detected fracture basement rock). Incorporating the geoelectric parameters value obtained and calculated reveal limited structural deformation of the basement rocks to yield fracture capable of creating secondary porosity in the area while the lithology of the weathered layers becomes the exploitable source for groundwater recovery in the study area.

Analisis Daya Dukung Tanah Dasar terhadap Kerusakan Jalan Raya Pule-Sarirejo

Roads are the main function as infrastructure for all forms of land transportation. For those who use the road, because a good road has a beneficial influence on the community, the road serves as the main foundation for economic turnover activities and social activities of the community. So comfort and tranquility when driving are very important factors before the construction of road pavement construction, the stability of a road must first be known the carrying capacity of the soil as a foothold. The carrying capacity of the soil that damages the pule-sarirejo road was evaluated by researchers. Factors affecting the decrease in soil carrying capacity were also studied in this study. Testing water content with an average value of 15.39% which includes high water content, data processing shows that the road bottom soil on Jalan Pule – Sarirejo has a low carrying capacity value in this test. For testing the boundaries Atterberg belongs to the group of clay soil types. with a PI value of 58.85% has a high platicity value. However, it is known from the results of CBR testing that the CBR value of the road base soil is 7.00%, included in the "sufficient" category and for the shear strength value is 0.21 kg/cm² and is still classified as sandy clay.

The effect of NPK fertiliser on oil palm coefficient as a baseline water management during the nursery phase

The Indonesian government views the oil palm industry as a promising sector for poverty alleviation. The germination process of seeds is influenced by water, requiring careful management. This study investigated the impact of NPK application and NPK fertiliser on the crop coefficient value of Tenera variety oil palm seedlings. The entisol soil used had a sandy clay texture, with sand comprising 81.00% of the soil composition. The soil texture, organic matter, bulk density, particle density, porosity, evapotranspiration, potential evaporation, percolation, moisture content at field capacity, and oven-dried root weight were measured with and without fertiliser to 50 oil palm trees at 3 to 6 months of age. The results show that NPK application has affected oil palm’s crop coefficient and growth. The highest dry root weight and plant coefficient obtained without fertiliser and with fertilisers at six months were 24.76 gr and 33.89 gr, 0.626 and 0.65, respectively. Root biomass, a sign of plant health and nutrient uptake, shows fertilization’s long-term effects. Six-month-old plants, especially fertiliser ones, have more extensive root dry weights, indicating persistent nutrition uptake and long-term resistance. Nutrient management is crucial to agricultural productivity, affecting the current crop and future growth phases.

Phytoremediation & Valorization of Cu-contaminated Soils Through Cannabis sativa (L.) Cultivation: A Smart Way to Produce Cannabidiol (CBD) in Mediterranean Soils

PurposeThe potential of industrial hemp (Cannabis sativa L.) for phytoremediation of copper-contaminated Mediterranean soils was investigated. The accumulation of copper in hemp’s parts and the effect of contaminated soil on the production of cannabidiol (CBD) were, also, of primary concern.MethodsTwo soil types, a Clay Loam & a Sandy Clay Loam, were exposed to two levels of Cu contamination, with low & high Cu concentrations. The soils’ total and available Cu content, along with Cu in plant tissues, were determined. Height, fresh aboveground biomass and leaf chlorophyll content were further evaluated. Furthermore, the amount of cannabidiol (CBD) in the hemp flowers was determined.ResultsHemp appeared to be highly resistant, as can successfully grow in both soil types having low or high Cu levels. The maximum Cu content was detected in the highest part of the plant roots, with a progressive decline towards the upper parts of the plant (CuRoots > CuShoots > CuLeaf), in both soil types. It has been observed that more than 50% of the plant’s copper concentration is accumulated in the roots. Furthermore, the hemp plants cultivated in high Cu-contaminated soils produced greater amounts of cannabidiol (CBD).ConclusionΗemp proved to be a promising plant for phytostabilization in Cu-contaminated soils, as its above-ground biomass is almost free of metals and can be used further for fiber production. The presence of Cu in soils did not appear to disrupt the production of the important secondary metabolite CBD, but rather increased following increasing soil Cu content.Graphical

Influence of Soil Type and Temperature on Nitrogen Mineralization from Organic Fertilizers

Organic vegetable producers in Georgia, USA, utilize a range of amendments to supply nitrogen (N) for crop production. However, differences in soil type, fertilizers and environmental conditions can result in variability in N mineralization rates among commonly utilized organic fertilizers in the region. In this study, the effects of temperature on N mineralization from three commercial organic fertilizers [feather meal (FM), pelleted poultry litter (PPL) and a mixed organic fertilizer (MIX)] in two soil types from Georgia, USA (Cecil sandy clay loam and Tifton loamy sand) were evaluated for 120 d. Net N mineralization (Net Nmin) varied with soil type, fertilizer and temperature. After 120 d, Net Nmin from the FM fertilizer ranged between 41% and 77% of total organic N applied, the MIX fertilizer ranged between 26% and 59% and the PPL fertilizer ranged between 0% and 22% across all soil types and temperatures. Incubation at higher temperatures (20 °C and 30 °C) impacted Net Nmin of FM fertilizer in the Tifton series soil. Temperature and soil type had a relatively minor impact on the potentially mineralizable N of the PPL and MIX fertilizers after 120 d of incubation; however, both factors impacted the rate of fertilizer release shortly after application, which could impact the synchronicity of N availability and plant uptake. Temperature-related differences in the mineralization of organic fertilizers may not be large enough to influence a grower’s decisions regarding N fertilizer inputs for vegetable crop production in the two soils. However, organic fertilizer source will likely play a significant role in N availability during the cropping season.

Development of eco-friendly clay ceramics using rice husk ash as a secondary mineral source of quartz

The study focuses on the sustainable reuse of waste ceramic materials, particularly rice husk ash (RHA), as a secondary mineral source in ceramics production. RHA's potential to replace primary raw clays in making ceramic blocks and bricks is explored. RHA is categorized as Class II-A non-inert waste, limiting its use to controlled applications like the ceramic industry due to environmental and health risks. The study assesses the feasibility of incorporating RHA into three different types of clay: yellow and black plastic clays (plastic) and sandy clay. Waste classification according to environmental and health risks follows ABNT NBR 10004/2004 guidelines. Various analytical techniques, including X-ray fluorescence, X-ray diffractometry, differential thermal analysis, and thermogravimetric analysis, were employed to characterize the materials. Laser diffraction measured the particle size distribution of the clays. In addition to the conventional ceramics industry standard formulation (STD), the study prepared five different mixtures with varying RHA and clay contents. These mixtures underwent evaluation for properties such as thermal shrinkage, density, porosity, water absorption, and diametral mechanical strength, with resistance reliability assessed using Weibull distributions. Results indicated that introducing over 15% RHA into clay ceramics led to excessive water absorption, rendering it unsuitable. Consequently, an 8.3% RHA content was chosen to manufacture hollow ceramic blocks for non-load-bearing masonry. This industrial test demonstrated favorable processing conditions compared to the STD, highlighting RHA's potential as an alternative raw material for the ceramic industry, contributing to sustainable development.

A review of mix design terminologies for cement admixed sandy clay

In densely populated countries, underground construction and land reclamation could be possible options to solve the demand for land space, thus securing sustainable long-term development of the nation. For example, in Singapore, land reclamation has been widely conducted using excavated materials from underground development. The excavated materials are commonly marine clays that contain sandy soils. To improve the mechanical properties of these soft soils, cement-treated soil stabilization is popularly adopted. In fact, many researchers have investigated the properties of pure cemented clay or pure cemented sand using conventional design parameters such as water content (water/solids) and cement content (cement/dry soil). However, can these terminologies be still used to accurately examine the role of sand in cemented sandy clay mixtures? Through unconfined compression testing, it is herein shown that the use of existing mix design approaches in the literature cannot properly explain the variation of strength with sand content for cemented sandy clay mixtures. A new mix design approach is thus proposed in this study, which ensures that the role of sand in a cemented clay matrix can be quantified.

Effects of the application of anaerobically digested sewage sludge on the consistency limits and compaction characteristics of differently textured soils

Notwithstanding their beneficial characteristics, the agricultural utilization of organic wastes may have an adverse effect on soil properties if used improperly. To evaluate proper use, a laboratory study was conducted to investigate the effects of different sewage sludge application doses (0, 2, 4, and 8% weight/weight) on the consistency limits and the compaction characteristics of three differently textured soils. The application of sewage sludge significantly improved the consistency limits and reduced the compactibility. The efficacy depended on the amount applied. The rates of increase in liquid limit (LL) values at 8% sewage sludge were 58.7% for sandy loam, 43.4% for loam, and 16.2% for clay soil. As the application dose increased, the optimum moisture content (OMC) values increased and the maximum dry bulk density (MBD) values decreased. The highest application dose decreased the MBD by 9.5% in sandy loam, by 6.5% in loam, and by 13.7% in clay-textured soils. The rates of increase in OMC values were 73.4%, 53.8%, and 27.1%, for sandy loam, loam, and clay, respectively. The results presented in this study clearly indicated that the application of sewage sludge made the soils more resistant to mechanical forces, since the increase in the proportion of OMC over LL and PL implied that the soil was easier to till at higher moisture contents without any deformation, which also resulted in a higher workable range.

Impact of organic amendments addition to sandy clay loam soil and sandy loam soil on leaching process of chlorantraniliprole insecticide and bispyribac-sodium herbicide

The leaching of two pesticides, cholantraniliprole (CAP) and bispyribac-sodium (BPS) in sandy clay loam soil (soil A) and sandy loam soil (soil B) were examined, by soil columns under laboratory conditions. In addition, the effect of adding 5% biochar and wheat straw to the soils on the leaching of CAP and BPS was studied. It is clear from the results that BPS is more leachable than CAP in all soil columns, and more leached to soil B. It was found that the addition of biochar and wheat straw has a significant effect on the movements of these pesticides and can be used to reduce the environmental impact. For CAP, 71 to 97% and 84 to 97% were recovered from the soil A columns and soil B columns, respectively, while for BPS, 94 to 99% were recovered from columns of soil A and soil B.

임진강 유역 후기 구석기에 대한 시론적 연구

In the Imjin River Area, 7 major sites related to the Upper Paleolithic were excavated. The sites are located on the lava plateau, fluvial terrace and on top of the hillslope. The sites related with the lava plateau and fluvial terrace show differences in colluvium after sedimentation of alluvial deposits. And underwent a stable process of soilification towards the upper levels. Many of the Upper Paleolithic artifacts are identified within the upper clay deposits. On the other hand, the site on the hillside was subjected to repeated colluvium, and the artifacts were likely re-deposited.
 Stratum comparisons of sites indicate that Upper Paleolithic artifacts occur in light brown, dark brown, and reddish brown clay layers and brown sandy clay or clay layers. The reddish brown clay and brown sandy clay or clay layers are the last Middle Paleolithic~30,000BP, the dark brown clay layers are primarily of the first half of MIS 2 : before 20,000BP, and the light brown clay layers are the second half of MIS 2 : after 20,000 BP.
 Throughout all time stages, quartz and quartzite lithic raw materials are heavily utilized and small stone tools are common. However, tuff and obsidian are identified in second artifact layer of Samgeo-ri site of the first half of MIS 2, which is related with the emergence of blade and micro-blade techniques. In other sites, these lithic technologies are not identified, suggesting that a variety of technological choices were made in response to the demand for shaped tools and the availability of raw materials. From the seond half of MIS 3 to MIS 2, the size of the flakes becomes smaller, and the types of small stone tools become more diverse and smaller. However, PESQ(pièce esquillée) remains constant in size and is looks like excluded from the miniaturization of stone tools because of its function.

Assessment of Subsurface Competency Using Geotechnical Method of a Proposed Structure F.C.T Nigeria

Structural failure has been recently happenings mostly in the commercially populated states along the coastal line in Nigeria. As a result, an open field at a chosen location in Abuja, Nigeria, was investigated. For the purpose of this study, test bores were drilled and Standard Penetration Tests (SPT) were conducted at every 1.5 m interval up to a maximum depth of 12.0 m with the bearing pressure ranging between 20 kN/m2 and 1000 kN/m2 . 3 test bores’ were drilled within the plot location, and samples were obtained at the test bores locations for laboratory analysis. Findings revealed that subsurface lithology found at the site within the explored depths of 0.0 ~ 12.0 m is mostly silty sand, laterite, sandy clay, silty clay, clayey sand, and weathered rock. The findings from the sub-soils of the different places and their bearing pressures were computed with SPT N value. Building foun dations may be rigid raft foundations at a depth of 2.0 meters below the present ground level, according to bearing capacity values that range from 20 kN/m2 to 60 kN/m2 at 1.5 to 3.0 meters. The recommended building foundations take into account the sub-soil’s characteristics at the drilling places at a depth of between 1.0 and 3.0 meters. The structure might also be supported by frictional piles buried 10 meters beneath the surface.

Conversion of tropical secondary forest into agricultural land: consequences for soil health and environmental stability

The objective of the study was to address the impacts of tropical forest conversion into agricultural land on changes in invertebrates’ communities, as well as soil chemical properties across 2–4 texturally distinct soils in La Mé and Grand Lahou, Côte d’Ivoire. The fieldwork was carried out in the humid period on two study sites: 1– rubber landscape (secondary forest, 7-, 12- and 25-year-old rubber plantations) and 2– oil palm landscape (secondary forest, 13-, 20- and 39-year-old oil palm plantations). Three sampling stands were established on each land-use type and age class, for a total of 24 sampling stands. Over a 40–50 m transect, topsoil (0–10 cm) invertebrates were sampled by using monoliths (50 cm × 50 cm × 10 cm), following the modified ‘Tropical soil biology and fertility’ method. Soils chemical properties were also determined. The results highlighted a decrease in taxonomic richness (–35 % and –42 %), Shannon index (–32 % and –37 %), Margalef index (–34 % and –41 %), soil carbon stock (–41 % and –15 %), nitrogen stock (–38 % and –11 %) and carbon sequestration (–41 % and –15 %), respectively, after the transformation of secondary forests into rubber and oil palm plantations. The clay soils and clay sandy soils favored the development and emergence of the soil invertebrates, and allowed a higher carbon and nitrogen storage, as well as a greater carbon sequestration. Whatever the site, the soil quality was more degraded under the monoculture tree plantations compared to the secondary forests. Our findings suggest leaving residues of the previous crop on the soil surface and the incorporation of woody trees with an understory of smaller trees during the early establishment periods of monoculture tree plantations, which can create a sustainable agroforestry system with improved nutrient recycling and soil fertility.