Soil Physical Parameters Research Articles

Sugarcane Yield Using Minimum Tillage Technology Through Subsoiling: Beneficial Impact on Soil Compaction, Carbon Conservation and Activity of Soil Enzymes

Adverse effect of intensive tillage practices on soil chemical and biological properties is already known. Soil organic carbon maintains porosity, releases nutrients for crop growth and also provides shelters to microbes. However, maintaining soil organic carbon at higher level and increasing crop productivity have become two faces of a single coin. Without addressing both issues simultaneously, the sustainability of production system will be far away. Strategic tillage intervention in no-tillage plots for sustaining long-term productivity is gaining importance. Strategic tillage through subsoiling/ripping of soil up to 45 cm depth at about 1 m spacing before sugarcane planting is feasible in sugarcane-based system. Thus, keeping the above points in view, the experiment was conducted during 2015–2017 with hypotheses of (i) whether the minimum tillage (once subsoiling) could maintain soil physical, chemical and biological parameters to sustain sugarcane productivity for longer period and (ii) how the mouldboard ploughing and/or conventional tillage practice affects these parameters and crop yields. The experiment was laid out in four preplant tillage treatments, i.e., one subsoiling (SS) and two harrowings, minimum tillage through subsoiling and direct planting of sugarcane through IISR Cutter Planter (SS), one ploughing through mouldboard plough and two harrowings (MBP + H) and conventional practice (CP—two ploughings through cultivator and one through rotavator) with six replications in randomized block design. The effect of these treatments was recorded on various soil physical, chemical and biological parameters vis-a-vis infiltration rate, cumulative infiltration and optimizing sugarcane yield in subtropical India. The results concluded that minimum tillage and direct planting of sugarcane through Sugarcane Cutter Planter could break hard impervious layer and improve soil physical, chemical and biological parameters besides improving sugarcane and sugar yields. Minimum tillage favoured build-up of soil organic carbon (SOC) and also release of nutrients for crop growth, which optimized rhizospheric environment as compared to conventional practice. Minimum tillage through subsoiling had shown major effect in reducing soil compaction in subsurface layers (bulk density—1.52 Mg m−3 (SS) vs 1.61 Mg m−3 through MBP + H). During tillering period, basic infiltration rate could reach the level of 7.5 mm/hr in SS plots compared to 5.5 mm/hr in conventional practice (CP). Minimum tillage recorded the highest SOC at all the crop growth stages. The highest mean SOC was recorded during grand growth phase (13.51 Mg ha−1). Minimum tillage altered lower amount of soil and showed the highest population of soil bacteria (log10 6.90x 105). Thus, the minimum tillage through subsoiling significantly improved sugarcane (96.32 t ha−1) and sugar yields (12.14 t ha−1) as compared to conventional tillage/mouldboard ploughing.

Water erosion modeling by the Erosion Potential Method and the Revised Universal Soil Loss Equation: a comparative analysis

Water erosion is the principal degradation process of tropical soils, and its effects can be measured by modeling techniques. Erosion models provide a diagnosis of the soil loss intensity and can support the planning of soil conservation practices. Models with low data requirements, such as the Revised Universal Soil Loss Equation (RUSLE) and, more recently, the Erosion Potential Method (EPM), are mainly applied in Brazil. Thus, the objective of this work was to estimate water erosion soil-loss rates using the EPM and RUSLE models on a tropical subbasin, followed by a comparison of their outcomes. The models’ application considered soil physical parameters, edaphoclimatic conditions of the area, land use, and subbasin management practices. The accuracy of the methods was verified using total transported sediment and water discharge data. We compared the models using Pearson's correlation analyses, considering a 5% of significance. We found a predominance of moderate-intensity erosion with average soil loss of 1.17 and 1.46 Mg ha-1 year-1, measured by EPM and RUSLE, respectively. The EPM model underestimated soil losses by 15.27%, and RUSLE overestimated by 19.08%, indicating a higher percentage of areas with high erosion rates (4.60%). The models presented results with a different order of magnitude, but with significant correlations, indicating that both methods pointed out similar zones of intense and light-erosion rates.

The Use of a Two-Dimensional Electrical Resistivity Tomography (2D-ERT) as a Technique for Cadmium Determination in Cacao Crop Soils

Cadmium (Cd) is a non-essential heavy metal naturally occurring in the earth’s crust or due to anthropogenic activity. The presence of this metal in cacao farm soils represents a significant issue as levels are now regulated in products derived from cacao beans (Theobroma cacao L.). Several strategies have been proposed to measure cadmium levels; however, little is known regarding in situ non-destructive and time efficient techniques to analyze Cd contents in both cacao topsoils and subsoils, particularly nearby the root system. Therefore, this research aims to integrate the physical property of soil resistivity to Cd content in cacao soils. Cd hot spots are estimated from resistivity measurements using a two-dimensional electrical resistivity tomography (2D-ERT) technique and correlated to Cd determination using inductively coupled plasma optical emission spectrometry (ICP-OES). To assess the dynamics of soil Cd content the correlation is discussed with other physical chemical parameters of soils (pH, organic matter, Ca, Fe, and P). The study was performed in 27 cacao farms in Colombia. A farm in Santander district proved to have the highest level of Cd using the correlated techniques (2.76 mg·kg−1 Cd and 1815 Ohm·m) followed by farms in Boyacá and Arauca districts (2.6 and 0.66 mg·kg−1 Cd, related to 1616 and 743 Ohm·m, respectively). A high correlation between 2D-ERT and Cd determination (R2 = 0.87) was found. The discussion regarding the soil parameters analyzed suggests that the 2D-ERT technique could be used as a preliminary approach to explore Cd distribution in cacao soils.

Knowledge gaps in organic research: understanding interactions of cover crops and tillage for weed control and soil health

Organic crop systems rely on tillage as the primary means to control weeds, but negative impacts of tillage may prevent farmers from achieving the potential soil health benefits of organic management. Cover crops have been suggested as a solution for overcoming this tillage trade-off directly by enhancing soil health and indirectly by providing weed control, thus reducing the need for tillage. In order to characterize the state of published research on the effects of cover crops on weed control and soil health in organic crop systems, we conducted a formal literature search on this topic and identified 116 relevant studies which were subsequently categorized by research focus, management strategy, and variables measured. We found 83 studies examined effects of cover crops on weed control and 33 studies examined effects of cover crops on soil health, but only 10 of the studies reported on both weed control and soil health effects. The lack of integrated studies examining both weed control and soil health responses to management highlights a research gap not sufficiently addressed by researchers, even though it is a topic of great interest to many organic farmers. A majority of studies (79) included reduced or no-till treatments, and annual grasses, clover, and vetch species were the most common cover crops. Assessments of aboveground biomass were the most common weed control measurements, while soil organic matter was the most common soil health measurement. Recommendations for future research needs include the following: more integrated assessments of the effects of cover crops on both soil health and weed control under varying tillage regimes; greater effort to characterize the soil health impacts of cover crop systems utilizing newly developed soil health indicators including soil physical parameters; long-term studies to assess dynamic soil health responses as well as perennial weed pressure (particularly in reduced and no-till organic systems); and greater allocation of research funding to regions outside of North America and Europe.

Impact of Application of Fertilizer and Lime on Yield of Banana (Grand Naine) and Soil Parameters in Acidic Soil of Arunachal Pradesh

The present study was aimed at standardizing fertilizer and lime requirement for tissue banana (Grand Naine) cultivation in acidic soil of mid hill of Arunachal Pradesh The experiment was conducted at ICAR RC farm Gori, ICAR RC for NEH Region, AP centre, Basar. The effect of twelve different treatments of combination of fertilizers and Lime was studied on growth parameters of banana plant, post harvest fruit quality parameters and on the soil chemical and physical parameter their availability & uptake of major nutrients were also studied. The results revealed. Plant growth parameters like pseudo stem circumference (36.96 cm) and Plant height (92.85 cm) was highest in the treatment receiving L1F2. Similarly, treatment L2F2 recorded highest number of leaves (5.96), suckers (1.41) and leaf area (3586 cm2). Treatment L2F1 recorded lowest stem circumference (22.3 cm), number of leaves (3.52) and leaf area (1420 cm2). Similarly, treatment having L3F1 recorded lowest number of suckers (0.41). The plants treated with (50% lime + 100% RDF) performed best in terms of both yield and quality attributes. The effects of lime application significantly improve pH of soil that resulted in the improved the availability of phosphorous. Application of 125% fertilizer was not found to significantly enhance the yield of Banana. The lime application significantly improve the soil nutrient concentration Viz Available N, P K, Ca pH and reduced Al concentration that resulted into enhance banana production compare to the control.

Projected changes in corn crop productivity and profitability in Parana, Brazil

We investigate the impacts of climate changes in corn crop profitability and productivity in Parana (Brazil), using SISDRENA model, considering different spacings between drains. SISDRENA model is used as input, daily precipitation, and potential evapotranspiration, properties of the drainage system, data of crop requirement, and physical and hydrological soil parameters. We use climate data from the Eta model. The baseline period of the simulation is from 1981 to 2005. For the future projections, we use the greenhouse gas emission scenarios RCP4.5 and RCP8.5, from 2046 to 2070. We concluded that there are variations in evapotranspiration over the years in the historical simulation, but in the future, this variability tends to be higher. There is a tendency for increased evapotranspiration in both scenarios in the future. We found a large variability of precipitation in both historical simulation and future projections. Changes in precipitation depend on location. In terms of both profitability and productivity, the 10-m spacing between drains is the most recommended. In historical simulation and future projections, it is found large variability in corn productivity over the years. We found that there is no agreement between RCP4.5 and RCP8.5, which shows uncertainty in the results. In general, in RCP4.5 the tendency is to increase 3% of productivity (not significant), while in RCP8.5 the tendency is to decrease 1% (significant), compared to the baseline period. This research contributes to better farmer management and decision making, providing recommendations for the best layout for current and future climate, and indicates trends in corn productivity in future scenarios.

Digital photography as a tool for microscale mapping of soil organic carbon and iron oxides

Digital cameras are becoming increasingly popular in environmental sciences and proximal soil sensing as low cost, but high quality and high-resolution sensors. The high spatial resolution of the images shows a great potential for mapping predicted soil properties at small scales, from soil profiles to the microscale. To explore the potential of digital cameras for the morphometric analysis at a fine scale, we took 50 samples plus 3 microplate scale excavations from a profile wall of a Luvisol and analyzed samples for soil organic carbon (SOC) and Fe content for model calibration. Images of sieved and ground soil samples were taken under standardized laboratory conditions. After image correction, RGB colors were obtained for each sample and transformed into different color space models. Based on the obtained soil colors, different regression models were built to predict SOC and Fe content. Simple regression produced predictions with R2adj values of 0.90 for SOC (using HSV V) and 0.70 for Fe (using CIE a*) for ground soil samples. For sieved samples, R2adj values were lower with 0.69 for SOC using HSV V and 0.61 for Fe using CIE a*. Multiple linear regression models with interaction terms could improve those predictions for sieved samples to R2adj values of 0.94 for SOC and 0.89 for Fe, using the complete HSV and CIELab color tristimulus, respectively. Based on the best pedotransfer functions, we predicted SOC and Fe contents for the excavated microplates at a 1 × 1 mm resolution. With this method we were able to map the microscale variability of SOC and Fe content with great accuracy. This study showed, that accurately calibrated digital images can be a cost-effective method to map the distribution of SOC and Fe and potentially other soil physical and chemical parameters at a very fine scale.

Soil-Root Dynamics in Maize-Beans-Eggplant Intercropping System under Organic Management in a Subtropical Region

Intercropping is an agricultural system that facilitates mutualistic and commensalist interactions among crops. The objective of this research was to test the hypothesis that intercropping with greater plant richness produces more roots that improves microbial activity, which in turn, contributes to soil physical structure that improves soil chemistry parameters, crop yield, and land use. We performed a field experiment in a randomized block design, utilizing beans (Phaseolus vulgaris), maize (Zea mays), and eggplant (Solanum melongena), under monoculture or intercropping systems. Root and soil biological, physical and chemical parameters, crop yield and land equivalent ratios were analyzed. Increased plant richness as a function of the intercropping system did not affect root and soil parameters. However, principal component analysis indicated that intercropping affected root density, mass, and length, which, in turn, contributed to the formation of soil aggregates, increased microbial activity and to the improvement of soil chemical parameters. Furthermore, as consequence of increased plant richness, the maize-beans-eggplant intercropping facilitated the positive interactions among the species and led to a Land Equivalent Ratio (LER) 60% higher than the monoculture systems. The production of roots in the crop systems, regardless of species richness, stimulates soil biological activity and affects the quality of physical structure and fertility indicators of the soil. Crop systems with higher richness of plant species promote positive interactions between plants and soil and results in a better land use ratio.

Study on the use of sludge farming of catfish as organic fertilizer and evaluate its effectiveness in agriculture

The purpose of this study is to reuse fishpond sediment to produce organic fertilizer for planting maize. The sludge was mixed with rice husk and Composted under aerobic conditions. The effectiveness of Compost on planting maizes was assessed by adding to maizes with and without combination chemical fertilizers as different dosages as recommendations. The amounts of Compost adding for maizes were 10 and 20 tons/ha. Maize growth, characteristics of corn, and soil physical and chemical parameters such as bulk density, soil aggregate stability, the volume of moisture, and useful moisture of soil were measured and evaluated. The results showed that the quality of organic fertilizer produced from waste sludge met Vietnamese standard (QCVN:2018/BNNPTNT) for adding to crops. Applying organic fertilizer with the quantity of 20 tons/ha to combine with the recommendation of inorganic fertilizer amount for planting maizes increased the yield. Moreover, 20 ton/ha of organic fertilizer coupling with 50% of chemical fertilizer amount as a recommendation for planting maize also enhanced the yield to compare with the control (only using inorganic fertilizer as a recommendation). The maize yield of applying 20 tons/ha of organic fertilizer was higher than the maize yield of 10 tons/ha of organic fertilizer. Using organic fertilizer produced by fishpond sediment did improve not only the soil quality but also protected the canals and increased household income.

Evaluation of the spatial variability characteristics of the unsaturated clay in Hefei, China

Soil properties (or parameters herein) vary randomly in space because of different depositional conditions. The knowledge of the spatial variability characteristics of unsaturated soils can be critical to the reliability assessment of geological and geotechnical engineering problems such as the stability analysis of unsaturated soil slopes and the seepage analysis of earth dams. To investigate the spatial variability characteristics of unsaturated soils, the soil parameters, including physical, deformation, and hydraulic properties, are measured through laboratory tests in this study. It is found that the variability of the physical parameters is smaller than that of the deformation parameters, and smaller than that of the hydraulic parameters. Five existing methods are adopted to evaluate the horizontal and vertical auto-correlation distances that measure the spatial variability, and it is found that the space average method and the correlation function method are more suitable for evaluating the auto-correlation distances when the number of test data is small. To further explore the spatial variability characteristics, the Wilcoxon rank analysis is conducted, and the results show that the auto-correlation distance is an inherent property of soils and there is little difference among the results obtained based on the physical, deformation, and hydraulic parameters of the unsaturated soils.

The Effects of Catch Crops and Tillage Systems on Selected Physical Properties and Enzymatic Activity of Loess Soil in a Spring Wheat Monoculture

This study was aimed at comparing physical soil quality parameters and soil enzymatic activity in a three-year spring wheat monoculture affected by the incorporation of biomass of selected catch crops into the soil using two systems of tillage (conventional plough tillage and conservation tillage). We tested the suitability of the following catch crop plants: white mustard, lacy phacelia, and mixed legumes (faba bean + spring vetch) and compared these to the control treatment. This research was carried out in the period 2014–2016 in Czesławice (central Lublin region, Poland). Catch crops promoted improved soil structure, soil particle-size distribution, soil bulk density, and soil moisture content. Tillage systems had a smaller impact on the soil physical parameters. Plough tillage contributed to improved soil moisture content in a deeper layer (15–20 cm). On the other hand, the above-mentioned tillage system influenced adversely soil compaction and bulk density. Catch crops caused an improvement in the soil particle size distribution, resulting in a higher percentage of the finer soil fractions. Moreover, the catch crops positively affected soil bulk density and soil compaction. The study has proven that enzymatic tests are good indicators to discriminate between soil sites under study in dependence on the catch crop and tillage system. Conservation tillage significantly stimulated the activities of the studied enzymes, especially in the topsoil layers. A particularly wide range of dehydrogenase and urease activity was obtained in the soil sown with the white mustard catch crop. The other catch crops (lacy phacelia and faba bean + spring vetch) also stimulated enzymatic activity. The obtained results show the positive role of catch crops and conservation tillage in bringing about positive changes occurring in the soil environment.

Effect of irrigation water quality on soil properties and infrared spectroscopic signatures

Aim of study: To study the effect of irrigation with medium-to-low-quality water on an olive farm that seems to be causing salinity and/or sodicity problems in soils, and the ability of infrared spectroscopy to detect this problem.Area of study: The study was conducted in an olive (Olea europaea L.) grove located in Guarromán (Jaen, Spain), on the boundary of the Sierra Morena Mountains and the Guadalquivir Depression.Material and methods: The olive farm is cultivated over two soil typologies, a calcareous area (carbonated) dominated by Regosols and a siliceous area with Leptosols. Typical soil physical and chemical parameters were determined, as well as near and mid infrared spectra were collected for analysis.Main results: Soil physical properties were affected by irrigation, with low infiltration rates and symptoms of structural degradation. Chemical properties were also altered, showing high pH, low amounts of organic carbon and N, and high sodium concentrations. These effects were stronger in the samples directly affected by the irrigation bulb, with the siliceous soils more affected than carbonated, probably due to the positive effect of the higher amounts of calcium in the latter. Using infrared spectroscopy, it was possible to discriminate the samples of this farm affected by sodicity from similar soil samples in Jaen province not affected.Research highlights: the use of medium-to-low quality irrigation water affected soil physical and chemical properties. Infrared spectroscopy could be useful for quick assessment of soil quality and soil degradation from salinity and sodicity.

Growth inhibition of acacia (Acacia nilotica) with seawater and shade

This research investigated the effect of the concentration of seawater (AL) and light intensity on seedling growth of A. nilotica. The research method used a randomized block design (RBD) factorial design with two factors. The first factor is seawater with 6 levels of concentration (AL 0%, 20% AL, AL 40%, AL 60%, 80% AL and AL 100%). The second factor is the shade with three levels of shade (55% NG, NG 65%, and 75% NG). The results showed: (1). Single factor shade and seawater has an inhibitory effect on the percentage of deaths tillers of A. nilotica, each treatment have different effects. The most effective combination inhibited A. nilotica growth was NG3AL5 (shade 75% and 100% concentration of seawater). (2). Seawater treatment affects the tissue organ damage of A. nilotica plants, especially roots and stems, therefore at 14 MST most of the test plants die for not being able to tolerate the treatment, (3). The analysis results of the soil physical and chemical parameters showed that no symptoms of poisoning the soil due to seawater treatment in the test medium, as shown by the high levels of every physical and chemical parameter of land far above the exposure limit.

Quantitative assessment of landslide risk using Monte Carlo material point method

PurposeThe purpose of this paper is to provide an effective way to assess landslide risk quantitatively. Quantitative assessment plays an important role in mitigating the landslide risk and developing a landslide risk-based warning system. However, efficient risk assessment on the large deformation failure process of slope with spatially variable soils is a challenging problem.Design/methodology/approachCombining the Monte Carlo simulation (MCS) and the higher-order material point method – the B-spline Material Point Method (BSMPM) – the concept of MC-BSMPM to assess the landslide risk quantitatively is proposed in this paper. The overall dynamic evolution of soil slope failure has been simulated by the BSMPM, and the probability density function of the sliding duration, the sliding kinematic energy, the sliding mass and the sliding distance of the landslide are obtained based on the MCS. Through the four risk assessment parameters of the sliding duration, the sliding kinematic energy, the sliding mass and the sliding distance, the landslide risk could be assessed quantitatively.FindingsIt is found that the post-failure behavior of the landslide conforms well to a normal distribution as the soil physical parameter is in a normal distribution. The variation of soil’s shear strength affects the dynamic motion of the landslide greatly.Originality/valueThe result shows that the landslide hazard cannot be estimated comprehensively by the deterministic BSMPM, while the landslide risk could be more clearly understood and quantitatively assessed with more details by the proposed method, which demonstrates that the MC-BSMPM method is an effective way to assess the landslide risk quantitatively.

Instrumentation of Infiltrometers with Arduino to Determine Soil Water Infiltration Rate

The intense mobilization of the soil inappropriately causes a reduction in the percentage of macropores and in the rate of soil water infiltration with reduction of crop yield. Due to the difficulty of using the Muntz concentric ring method, researchers have used mathematical models to estimate infiltration based on soil physical parameters such as, soil texture that does not reflect physical reality in relation to infiltration rate, leading to errors. To automate the use of the infiltrometer ring method, there are no hydrometers that record small flows in non-pressurized hydraulic systems, making it difficult to automate the method for field determination. For this purpose, six Muntz double rings were instrumented with an electromechanical system coupled to the “Tipin Buked” (weighbridge) with the ability to record flows from 8 cm3∙minute−1 on a memory card. The results indicate that the models of the regression equations describe 93% to 99% of the real values, showing the accuracy of the equipment. This work aimed to modify the Muntz method to reduce field work and automate the determination of water infiltration rate in the soil.

Increasing crop diversity in wheat rotations increases yields but decreases soil health

AbstractDemand for food is rising and the ability of any particular soil to support sustainable food production is dependent upon a variety of soil biochemical, chemical and physical soil parameters. However, the challenge is that the impacts of a new management practice on soil properties may take years to assess. In this field study, we investigated the effects of long‐term cropping rotation treatments (established in 2001) on soil health indicators from soils under monoculture, 2‐yr and 3‐yr crop rotations with and without a cover crop. In particular, we compared soil heath indicators under eight cropping sequences including continuous winter wheat (Triticum aestivum L.) (WW), soybean (Glycine max L.)–winter wheat (S–WW), corn (Zea mays L.)–soybean–winter wheat (C–S–WW), and winter wheat–soybean–soybean (WW–S–S) all with and without red clover (Trifolium pretense L.) (RC) in the wheat phase of the rotation. We measured ten soil health indicators collected from the wheat phase of the rotation. Crop rotation had greater effects on soil health indicators than cover crop. After 17 years, crop yields were 23–28% greater for the 2‐yr and 3‐yr rotations than monoculture WW in the presence of red clover. In the absence of red clover, yields were 32–39% greater for the 2‐yr and 3‐yr rotations than monoculture WW. However, the soil health indicators were significantly greater for monoculture WW than the 2‐yr and 3‐yr rotations. These results suggest WW enhanced soil health while crop rotations with soybean negatively impacted most biochemical soil health parameters.

A Comparative Study of Protective Schemes for Shield Tunneling Adjacent to Pile Groups

Shield tunneling adjacent to pile groups is always an unavoidable problem in urban metro construction. A case was found in the project of Tianjin Metro Line 7, where a shield tunnel would be constructed near the existing pile groups of Shiyou Bridge. The whole shield tunnel is close to pile groups, and the minimum distance is only 0.8 m. Therefore, four kinds of protective schemes are proposed in this paper. It is vital to select an appropriate protective scheme to guarantee the safety during the tunnel construction. In this study, the main mechanical characteristic and physical parameters of site soil were obtained through laboratory tests. Besides, the three‐dimensional finite element method was carried out to compare and analyze the effectiveness of the protective schemes in mitigating the effects of tunneling on adjacent pile groups. The results show that the deep‐hole grouting scheme has better control effect on the lateral deformation and bending moment of piles, while the pile foundation underpinning scheme has better effectiveness on reducing the settlement of bridge structure and ground deformation. Finally, the deep‐hole grouting reinforcement scheme will be adopted to ensure the shield passing through the pile groups smoothly.

Оперативное построение модельной кривой деформирования по данным волнового анализа

The paper presents the study results of the currently used nondestructive technique of multichannel analysis of surface waves which is adapted for express assessment of physical and mechanical parameters of dispersive soils during preliminary geotechnical investigation of the construction site. The authors propose a methodology for express plotting of model deformation curve of dispersive soil based on the wave analysis data, which will allow a rapid and non-expensive estimation of allowable load intervals and deformations under these loads with preliminary geotechnical assessment of foundation bases. The plotted deformation curve will be useful for obtaining initial data for numerical modeling of interaction of foundation base with the structure designed for the model of hardening soil and the model of hardening soil at small strains.

Green waste compost with wood ash additive improves physico-chemical and biological parameters of an Oxisol, and soybean (Glycine max L) yield

A greenhouse study was conducted to assess the potential of green waste wood ash compost on a tropical acid soil. Four types of compost (prepared with 0, 5, 10 and 15% of wood ash prior composting) were used to amend an Oxisol from the centre region of Cameroon. The different composts were mixed with the soil in 1/4 proportions (w/w); the experimental design was a completely randomized block with three replicates per treatment. The different treatments were planted with soybean (Glycine max L.) for three month growing period. Compost amendment increased the soil pH, organic carbon, total nitrogen and total phosphorus. Bacterial and fungal biomass together with cellulase and protease activities also increased in amended soil. Following soil chemical, physical and chemical parameters, plant growth and yield also improved in compost treated sols. However, compost prepared with 15% wood ash additive showed trends of inhibition of the soil microbiota. It can be concluded that green waste wood ash compost could be used as a suitable soil fertilizer for tropical acid soils, although precautions are to be taken when using these composts prepared with addition of wood ash ≥ 15%.

Changes in surface soil properties and macroinvertebrate communities with the conversion of secondary forests to oil palm (Elaeis guineensis) plantations

The conversion of natural forest to oil palm (Elaeis guineensis Jacq.) plantation is perceived as a threat to biodiversity conservation. The aims of this investigation were to assess variation in soil physico-chemical parameters and macroinvertebrate structures following the conversion of secondary forests to oil palm plantations, and to understand what to expect with the aging of the plantations. We hypothesised that soil properties would be improved with respect to biodiversity conservation with the aging of the oil palm plantations. Sampling was carried out in secondary forests, and in 13-, 20- and 39-year-old oil palm plantations at the La Mé Station, Côte d’Ivoire. Three sampling areas were established in each land-use type and age class, for a total of 12 sampling areas. Over a 50-m transect, litter-dwelling macroinvertebrates were sampled by using pitfall traps, and topsoil (0–10 cm) macroinvertebrates by using monoliths (50 cm by 50 cm by 10 cm), following the modified ‘Tropical soil biology and fertility’ method. Soil physical and chemical parameters were characterised. The results showed that the conversion of secondary forests to oil palm plantations was characterised by changes in soil macroinvertebrate density (–30%), taxonomic richness (–37%) and functional groups (–17%), as well as soil bulk density (+14%) and water content (+16%), after ~39 years of conversion. Soil organic carbon, total nitrogen and organic matter increased with the aging of plantations, and reached conditions similar to those of secondary forests. The human interference imposed on macroinvertebrate communities during site preparation and planting was not compensated by the reduction in the soil-degradation index over time. The results have implications for implementation of conservation agriculture and the related management practices.