Marginal Soils Research Articles

Effect of Rabbit Manure on the Growth and Yield of Groundnut (Arachis hypogaea Linnaeus) Grown on Intensely Cultivated Ultisols of South Eastern Nigeria

Groundnut when planted on marginal or infertile soils, seldom performs well, except where appropriate fertilizer or soil amendment materials are applied. Field trials were conducted at the National Cereals Research Institute, Owot Uta substation near Uyo, to examine the effects of rabbit manure on the growth and yield of groundnut. The experiment consisted of three medium maturing groundnut varieties (Samnut, G-153 and Imata). The three groundnut varieties were treated to five rates of rabbit manure (0, 1.5, 3.0, 4.5 and 6.0(tonnes/ha)) in a 3×5 factorial arrangement. The experiment was replicated three times. Results indicated significant positive effects.

Planting date and tillage effects on yield and nutrient uptake of two sorghum cultivars grown in sub-humid and semi-arid regions in South Africa

IntroductionSorghum is emerging as a viable crop option to increase food production under changing climate due to its resilience to drought and marginal soils. Appropriate planting date, crop cultivars, type of tillage and rotations, under contrasting climatic conditions, could make significant contribution on the effective management of sorghum under changing climatic conditions. A short-term study was carried out to investigate the effects of planting date, crop cultivar, tillage type and rotations on the growth and primary nutrient uptake of sorghum in contrasting climatic regions.MethodsThe study was conducted in Free State - (FS) and KwaZulu Natal (KZN) Provinces of South Africa over two seasons (2020/21 and 2021/22). The two cultivars (Pan8816 and Macia) were sown in December (PD1) and in January (PD2) under conventional tillage (CT) and no-till (NT) and with two rotations (Sorghum-Cowpea-Sorghum and Sorghum-Sorghum-Sorghum) resulting in 2×2×2×2 factorial experiment.Results and discussionIn KZN, in both the first (2020/21) and second (2021/22) seasons, the effects of all the factors, except cultivar in the second season, were not significant on yield, and uptake of nitrogen (N), phosphorus (P) and potassium (K). In the second season, Pan8816 (4.40 t/ha) produced 3.3 times higher yield than Macia (1.32 t/ha), and took up higher N, K and P. In FS, the early planted sorghum (1.15 t/ha for season one; 3.39 t/ha for season two) had significantly higher yield than late planted sorghum (0.434 and 0.91 t/ha for seasons one and two, respectively). Furthermore, the early-planted crops took up higher N, K and P than when planted late, while Pan8816 took up 1.74 times more P than Macia. Plants grown under CT (2.61 t/ha) produced significantly higher yield than under NT (1.70 t/ha), with plants under CT taking up significantly more K than those grown on NT. These findings suggest that in the drier FS, early planting under conventional tillage, while in the wetter KZN, selecting the appropriate cultivar (PAN8816), are essential for sorghum grain yield, at least in the short-term.

Identifying phosphorus use efficient genotypes by evaluating a chickpea reference set across different phosphorus regimes

AbstractLow phosphorus use efficiency (PUE) is one of the abiotic factors that hamper yield and production potential in chickpea (Cicer arietinum L.). Higher yield coupled with improved PUE can make this crop more adaptive and competitive to wide cropland area, especially on marginal soils having low-level phosphorus (P). To identify chickpea germplasm lines that assimilate phosphorus more efficiently under P-deficient soils, 288 diverse genotypes of chickpea belonging to reference set were evaluated for yield component traits and PUE under field conditions for two consecutive years at two phosphorus levels (low P – no phosphorus application and high P – phosphorus application at 40 kg/ha). Based on 2-year evaluation of data under high and low P soil conditions, we identified strong correlations for traits like number of primary and secondary branches, number of pods, biological yield and seed yield indicating that these traits can be used as proxy traits for PUE. ICC 6571 was the best performing genotype under low P conditions while ICC 6579 yielded maximum under high P regime. We report 16 genotypes namely ICC 1052, ICC 1083, ICC 1098, ICC 1161, ICC 2072, ICC 4418, ICC 4567, ICC 4991, ICC 5504, ICC 5639, ICC 7413, ICC 8350, ICC 9590, ICC 9702, ICC 11584 and ICC 13357 as phosphorus use efficient genotypes based on their better performance for yield and yield-contributing traits under low P compared to high P conditions. These genotypes can be exploited in future as potential donors for development of phosphorus use efficient chickpea cultivars.

Miscanthus x giganteus biochar: Effective adsorption of pharmaceuticals from model solution and hospital wastewater

This study investigated the adsorption of pharmaceuticals, including atenolol (AT), 17-α-ethinylestradiol (EE2), and sulfamethoxazole (SMX), in model solutions and in the effluent from a hospital wastewater treatment plant. The pharmaceuticals were adsorbed on biochar prepared from Miscanthus x giganteus biomass obtained from the phytoremediation of contaminated or marginal soil. The feedstock was pyrolyzed at 360 °C (M-3) and 500 °C (M-5). The representation of functional groups, specific surface area, porosity, and pore volume were lower for M-5. Pore diameters were comparable, but their depth decreased for M-5. The specific surface area and porosity surface area of M-5 were 30 times higher after 4 h of shaking compared to properties without shaking. The biochar leachate pH was 9.8 ± 1.0 (M-3), and 11.1 ± 1.1 (M-5). No desorption of potentially risk organic compounds was detected. M-3 was generally a better adsorption material. The removal of EE2, AT and SMX was greater than 90%, 70% and 30 % respectively after 4 h in model waters. There was no evidence of a linear relationship between the sorption efficiency of pharmaceuticals and the biochar dose. Sorption experiments with real wastewater from a hospital wastewater treatment plant demonstrated high removal rates of monitored pharmaceuticals, including e.g. SMX (80%), trimethoprim (91%), venlafaxine (100%), clarithromycin (96%), tramadol (93%), diclofenac (86%). It was proven that the efficiency of the adsorption process is influenced not only by the dose or physico-chemical properties of the biochar, but also by the initial concentration of the pharmaceutical and its properties. The presence of other components of real wastewater, which can cause competitive sorption and overlapping of active centers on the surface of the biochar, also decreased the efficiency. The results demonstrate that both biochars are suitable for tertiary or quaternary water treatment for pharmaceutical removal. Due to the lower energetic, and therefore economic, costs of pyrolysis, a lower pyrolysis temperature can be preferred.

Tall wheatgrass response toward phosphorus deficiency: a constraint to its use as a forage resource in marginal soils

Tall wheatgrass is cultivated for pasture in marginal areas around the world due to its tolerance to abiotic stress including seasonal droughts and floods, as well as saline and alkaline soils. However, there is concern about its biomass productivity, which often does not exceed that of natural pastures. In this work we hypothesize that tall wheatgrass is a plant more sensitive to low P availability than commonly assumed. A glasshouse sand culture experiment was conducted to analyze morpho-physiological responses of tall wheatgrass to different P availability levels: 1 µmol L−1 phosphorus (severe deficiency, P1), 10 µmol L−1 phosphorus (representative value of soil solution in the region, P10) and 500 µmol L−1 phosphorus (full P supply, P500). Our results show that both limiting P conditions strongly decreased plant development and biomass accumulation, and altered above- and below-ground morphology, in comparison with P500 plants. The latter, in turn, had relative growth rate values comparable to those of other cultivated grasses under non-limiting conditions. In both P-deficient treatments, plant development was severely delayed starting from leaf number 3, even when P concentration in the pseudostem at early stages was similar or even higher than that of P500 plants. Our results suggest that developmental inhibition of tall wheatgrass at low P supply may be the consequence of a specific plant response to P concentration in soil solution, rather than to direct P starvation in plant tissues, and underlines the need of improvement of this species to enhance productivity in this environment.

Cocoa seedlings growth on marginal soil as affected by application of dry walnut leaf compost and arbuscular mycorrhiza fungi

Cocoa (Theobroma cacao L.) is a plantation commodity that is widely cultivated in Indonesia, this commodity is very important in Indonesia because it has played a role in the Indonesian economy since 1930. The problem faced in cocoa cultivation is the lack of nutrient availability due to chemicals that cause residue in the soil, resulting in the growth of cocoa seedlings are not optimal, to optimize the growth of cocoa seedlings, provide a mixture of organic fertilizer in the planting medium and provide mycorrhiza. This research used the basic pattern of a factorial Completely Randomized Design (CRD) consisting of 2 factors and repeated 3 times. The first factor is the dose of dry leaf compost (K) which consists of 3 levels, namely: Without dry leaf compost treatment/control (K₀), dry leaf compost 60 g/polybag (K₁), Dry leaf compost dose 120 g/polybag (K₂) and the second factor is the arbuscular mycorrhizal dose (M) which consists of 3 levels, namely: Without arbuscular mycorrhizal fungus treatment/control (M₀), arbuscular mycorrhizal dose of 15 g/polybag (M₁), and arbuscular mycorrhizal dose of 30 g/polybag (M₂) So there are 27 experimental units. The results of the study showed that (1) there was a real interaction between the treatment of compost dose (K) and mycorrhizal dose (M) in safety. The combination of compost dose (K) 120 g/plant and mycorrhiza dose (M) 30 g/plant (K2M2) was the best treatment combination. (2) The treatment of giving a compost dose (K) had a significant effect on the variables of plant height, number of leaves, stem diameter, and plant dry weight. The best treatment was a compost dose of 120g/plant (K2). (3) The mycorrhizal dose (M) treatment had a very significant effect on the variables of plant height, number of leaves, stem diameter, and plant dry weight. The best treatment was a mycorrhizal dose of 30g/plant (M2).

Prospects of crambe for the bioeconomy of the Swabian Alb in southwest Germany

Crambe (Crambe abyssinica Hochst. ex R.E.Fr.) is a drought-tolerant, non-edible annual oil crop with low fertilization needs, and there are compelling opportunities for crambe to capitalize on market growth in natural cosmetics and the regional sustainability. It is therefore proposed for cleaner biomass production on marginal land, and the development of novel value chains and webs in rural areas. Therefore, this study assesses the prospects for growing and processing crambe in the Swabian Alb, a rural area in southwestern Germany large parts of which are characterized by marginal shallow stony soil. A literature review, stakeholder questionnaires, and a SWOT analysis were used to assess crambe's potential in the region. This informed a locally adapted value web, which combines multiple value chains and stakeholders into one interlinked diagram showing present potential valorization opportunities for crambe in the region. However, it was found that it is not currently possible to implement a value web for crambe in the Swabian Alb. Instead, a single value chain involving farmers, cosmetics companies, and biogas plants is possible. To expand this value chain opportunity into a value web, more information is needed for all stakeholders. European Innovation Action projects could help by providing more information about crambe cultivation and by ensuring ecologic and social sustainability. Economic sustainability, however, will require the involvement of other stakeholders in the value web, so that supply matches demand. Local institutions and networks can share knowledge to grow the currently possible value chain into a broader value web. This approach could also be used in other regions to assess the sustainability of novel biobased value chains across social, economic, and environmental dimensions.

Effects of Different N Fertilizer Doses on Phenology, Photosynthetic Fluorescence, and Yield of Quinoa

Quinoa (Chenopodium quinoa Willd.) is gaining recognition as a pseudocereal due to its nutritional attributes and adaptability to challenging conditions and marginal soils. However, understanding the optimal fertilization for quinoa growth remains a challenge. This study investigates the effects of nitrogen fertilization (0, 90, 120, and 150 kg using urea) on quinoa phenology, growth, and photosynthesis in the Loess Plateau region of China, a critical area facing soil erosion and ecological degradation. The results showed that nitrogen fertilization significantly influenced quinoa phenology, prompting early flowering and shorter growth at an optimum rate of 120 kg ha−1. Nitrogen application enhanced growth traits such as plant height, stem diameter, and chlorophyll content, particularly at the heading and flowering stages. Photosynthesis-related parameters, including net photosynthesis rate, transpiration rate, stomatal conductance, and intercellular CO2 concentration, were affected by nitrogen application, with higher values observed at 120 kg ha−1. Non-photochemical quenching was significantly increased by nitrogen application, indicating the efficient dissipation of excess energy. The study demonstrated a positive correlation between grain yield and growth traits, photosynthesis-related traits, and chlorophyll content. In conclusion, quinoa yield could be significantly improved at the Loess Plateau region under rainfed conditions by an optimal nitrogen fertilizer rate of 120 kg ha−1, which reduces the growth duration while increasing photosynthesis traits.

Improving Tuber Yield of Tiger Nut (Cyperus esculentus L.) through Nitrogen Fertilization in Sandy Farmland.

The cultivation of tiger nut (Cyperus esculentus L.) on marginal lands is a feasible and effective way to increase food production in Northern China. However, the specific influence of nitrogen fertilizer application on the growth dynamics, tuber expansion, overall yield, and nitrogen use efficiency (NUE) of tiger nuts cultivated on these sandy lands is yet to be fully elucidated. From 2021 to 2022, we conducted a study to determine the effect of N fertilizers on the leaf function morphology, canopy apparent photosynthesis (CAP), tuber yield, and NUE of tiger nut. The results indicate that the tuber yield and NUE are closely related to the specific leaf area (SLA), leaf area index (LAI), leaf nitrogen concentration per area (NA), CAP, and tuber expansion characteristics. Notably, significant enhancements in the SLA, LAI, NA, and CAP during the tuber expansion phase ranging from the 15th to the 45th day under the 300 kg N ha-1 treatment were observed, subsequently leading to increases in both the tuber yield and NUE. Moreover, a maximum average tuber filling rate was obtained under the N300 treatment. These improvements led to substantial increases in the tuber yield (32.1-35.5%), nitrogen agronomic efficiency (NAE, 2.1-5.3%), nitrogen partial factor productivity (NPP, 4.8-8.1%), and nitrogen recovery efficiency (NRE, 3.4-5.7%). Consequently, 300 kg N ha-1 of N fertilizers is the most effective dose for optimizing both the yield of tiger nut tubers and the NUE of tiger nut plants in marginal soils. Structural equation modeling reveals that N application affects the yield and NUE through its effects on leaf functional traits, the CAP, and the tuber filling characteristics. Modeling indicates that tuber expansion characteristics primarily impact the yield, while CAP predominantly governs the NUE. Above all, this study highlights the crucial role of N fertilizer in maximizing the tiger nut tuber yield potential on marginal lands, providing valuable insights into sustainable farming in dry areas.

Evaluating the Efficiency of the Mine Workings Supporting Technology Application to Increase Contour Stability

Maintaining the mine workings will also require significant costs to repair them both before and after they are introduced into production, especially in the zone of influence of the mining operations. Maintaining and increasing the volume of underground coal mining is only possible with a highly efficient technology for conducting and maintaining preparatory workings. The purpose of the study was to assess the parameters for controlling the stability of the contours of mine workings secured by anchor support to create a technology for intensive and safe conduct of mine workings based on the identified patterns of behavior of the adjacent rock masses. The idea of the approach is to use the anthropogenic stress-strain state to develop an effective technology for securing the contour rock massif. The mechanism of rock deformation, shear and collapse in a structurally disturbed heterogeneous rock massif is studied to assess the state of the rock massif around mine workings. Technological prerequisites for anchoring the marginal soil rocks, taking into account the state of the rock mass around the excavation, are developed and the parameters of anchor support operation in mines to secure the rods in excavations to ensure the safety of mining operations are determined.

Early production of switchgrass (Panicum virgatum L.) and willow (Salix spp.) indicates carbon accumulation potential in Appalachian reclaimed mine and agriculture soil

AbstractThe production of bioproduct feedstocks such as switchgrass (Panicum virgatum L.) and willow (Salix spp.) on degraded lands provides an opportunity to grow dedicated bioenergy crops with the potential to capture and store carbon in the soil while reducing competition with land for food production. However, how the production of these crops alters plant–soil–microbe interactions that govern soil C accumulation in highly degraded soil is underexplored. The objectives of this study were to examine select biological and chemical properties related to stable soil organic matter (SOM) production from the growth of switchgrass and willow on marginal soil over two growing seasons and whether biochar amendment can positively affect these parameters. To address our objectives, paired former surface mined lands and non‐mine impacted marginal agriculture sites were selected across West Virginia, USA, and biochar and unamended control treatments were imposed. Through the first two growing seasons, microbial activity and demand for carbon (C) increased and was accompanied by a shift in extracellular enzyme investment for decomposition‐associated enzymes. Mineral‐associated organic matter C increased over the two growing seasons, and this increase was greater in the mine sites compared to the agriculture sites. Compared to each site's previous land use, C losses were observed under bioproduct systems in the agriculture, but not the mine sites. Biochar amendments did not impact microbial activity but did increase the C:N of SOM. Overall, our results suggest that the early growth of switchgrass and willow can result in C accumulation in marginal and highly degraded lands.

Linking marginal soil to sugarcane productivity in Takalar, Indonesia

Linking marginal soil to sugarcane productivity in Takalar, Indonesia

Effect of liming in plinthic and petroplinthic soils for soybean cultivation in the Brazilian Savanna

Agricultural expansion is advancing on marginal soils (Plinthic soils), but the liming recommendation for this soil, especially for soybean cultivation, remains unknown. This study aimed to evaluate soybean (Glycine max) responses to limestone doses in concretionary soils (plinthic and/or petroplinthic). The experiment was carried out in the greenhouse, in randomized blocks, with four soil types and six limestone doses (4x6 factorial scheme), with four replicates. Soils were: RYO: Red-Yellow Oxisols; CPP-29, CPP-72, CPP-82 corresponds to the Concretionary Petric Plinthosol with 29, 72, and 82% concretions, respectively. Limestone doses varied from 0 to 4 times for each soil, based on the recommendation of regional bulletins. Soil temperature, crop emergence, development, and soybean yield characteristics were evaluated. Results were evaluated by ANOVA, followed by the LSD test or polynomial regression adjustment (p ≤ 0.05). Soybean response to liming varied with soil types. Seedlings showed lower vigor in Plinthic soils with plinthite contents ≥72%. These soils showed higher thermal accumulation (°C), and this increase showed a strong negative correlation with soybean development and reproductive characteristics. Evidence of liming response was observed after crop stage V5. Limestone substantially improved soybean growth and development in Plinthic soils with high plinthite levels, although they had lower yield potential than low plinthite levels and Oxisol. In general, the maximum response of the crop occurred at doses ~2 times higher than that practiced in the Brazilian Savanna region, especially in Plinthic soils

Responses of growth, yield and chemical composition of tomato to phosphorus nutrition under different saline environments

Growing crops on marginal and salt-affected soils with saline water will be more important for agricultural production in the future. The most prevalent anions in saline soils, chloride (Cl-) and sulfate (SO4 2-) have distinct effects on plant growth, metabolism, nutrient composition, productivity, and nutrient requirements. In order to ascertain the role of phosphorus in mitigating salinity stress in tomato plants, a pot experiment was conducted in a screen house under two types of saline environments chloride-dominated (Cl-: SO4 2- = 7:3) and sulfate-dominated (Cl-: SO4 2- = 3:7), with two comparable ECe levels (non-saline and 6 dS m−1) and four graded phosphorus levels (0, 12.5, 25, 50 mg kg−1soil). The significant increase in yield up to 50 ppm added P indicated that plants require more P under chloride salinity than sulfate salinity. In non-saline, chloride, and sulfate-dominated conditions, increased P from 0 to 50 ppm increased chlorophyll 'a‘ and 'b‘ values by 21.4, 19.8 and 23.8% and 10, 20 and 14%, respectively. The reduced photochemical efficiency due to salinity, was increased 32%, 30% and 13% as P level increased from 0 to 50 ppm in non-saline, Cl--6 and SO4 2—6 conditions, respectively. The TSS, ascorbic acid content and titrable acidity of tomato fruits was improved with mild salinity stress but reduced with added P. The plant N, P and K content increased significantly with each added P level irrespective of types of salinity. The plant composition indicated an antagonism between phosphorus and chloride ions and synergism between phosphorus and sulfate ions.

Use of a rubber wood fly ash-based geopolymer for stabilizing marginal lateritic soil as green subbase materials

Use of a rubber wood fly ash-based geopolymer for stabilizing marginal lateritic soil as green subbase materials

Soil Physicochemical Characteristics and Spore Density of Indigenous Arbuscular Mycorrhizal Fungi (AMF) in Different Vegetation Patches of a Marginal Upland in Central Philippines

To show the importance of plant-microbe association in stressed tropical landscapes, the study evaluated the physicochemical characteristics and indigenous arbuscular mycorrhizal fungi (AMF) spore density in selected vegetation patches of marginal upland soils in Central Philippines. Five quadrats were used in the study, namely Andropogon aciculatus (control plot), Imperata cylindrica, Chromolaena odorata, Melastoma malabathricum and mixed vegetation patch. Results showed that soils in the studied vegetation patches had different physicochemical characteristics and AMF spore density. Although all patches had clay soil texture and comparable water-holding capacity, mixed vegetation patch had moderate compaction (1.33 g cm-3) and higher porosity (50.31%) compared with the other patches, which had extreme compaction (1.37-1.65 g cm-3) and lower porosity (37.74-48.76%). In terms of chemical properties, soils in different patches had moderate (5.69) to strongly acidic pH (5.13), moderate organic matter (2.69-2.91%) levels, low P (2.67-3.94 ppm) content and above critical K levels (0.2-1.2 cmol+ kg-1). Results also revealed that C. odorata patch had the highest spore density count (11.33 spores 100 g-1), followed by mixed vegetation (9 spores 100 g-1), M. malabathricum (8.33 spores 100 g-1), and A. aciculatus patch having the lowest spore density count (4 spores 100 g-1). The significant spore density variability was attributed to the differences in soil’s physicochemical characteristics among the different vegetation patches and AMF host specificity. Spores detection, therefore, indicated AMF presence and helped the adaptation mechanism of the natural vegetation in this degraded upland.

Limited effects of crop foliar Si fertilization on a marginal soil under a future climate scenario

Growing crops on marginal lands is a promising solution to alleviate the increasing pressure on agricultural land in Europe. Such crops will however be at the same time exposed to increased drought and pathogen prevalence, on already challenging soil conditions. Some sustainable practices, such as Silicon (Si) foliar fertilization, have been proposed to alleviate these two stress factors, but have not been tested under controlled, future climate conditions. We hypothesized that Si foliar fertilization would be beneficial for crops under future climate, and would have cascading beneficial effects on ecosystem processes, as many of them are directly dependent on plant health. We tested this hypothesis by exposing spring barley growing on marginal soil macrocosms (three with, three without Si treatment) to 2070 climate projections in an ecotron facility. Using the high-capacity monitoring of the ecotron, we estimated C, water, and N budgets of every macrocosm. Additionally, we measured crop yield, the biomass of each plant organ, and characterized bacterial communities using metabarcoding. Despite being exposed to water stress conditions, plants did not produce more biomass with the foliar Si fertilization, whatever the organ considered. Evapotranspiration (ET) was unaffected, as well as water quality and bacterial communities. However, in the 10-day period following two of the three Si applications, we measured a significant increase in C sequestration, when climate conditions where significantly drier, while ET remained the same. We interpreted these results as a less significant effect of Si treatment than expected as compared with literature, which could be explained by the high CO2 levels under future climate, that reduces need for stomata opening, and therefore sensitivity to drought. We conclude that making marginal soils climate proof using foliar Si treatments may not be a sufficient strategy, at least in this type of nutrient-poor, dry, sandy soil.

Large Triaxial tests on Marginal soil admixed with Randomly Distributed with coir fiber and fly ash

The Due to a lack of suitable granular soils, it has become necessary for various construction types to use marginal soils (soils of lower strength) at various work sites. Typically, soil with higher percentages of silt and clay (finer particles) exhibits unfavourable engineering characteristics, making it unsuitable for a variety of construction-related operations. These soils are typically possessing plasticity in nature and have low strength, especially when it comes to shear strength. Common approaches like admixture stabilisation are being implemented to enhance the strength characteristics of these soils. The quality of these marginal soils to make them amenable for construction is also being improved by the chemical additives. By adopting such procedures that involve chemical admixing for the process of modifying marginal soils, the cost of construction process rises. In this work, an effort was undertaken with regard to examine the efficacy of modifying marginal soil admixing with cement/lime and with dispersed randomly with coir fibre as reinforcing material. Additionally, shear testing was carried out by admixing fly ash. The objective of the present work is to investigate the shear strength characteristics modified marginal soil and could be affected by the reinforcement of coir fibres. Using the proposed marginal soil, a number of significant triaxial laboratory works were carried out. The experimental study is intended to provide a workable answer for increasing the shear strength of marginal soil. It was observed that the shear strength of marginal soil modified/admixed with ordinary Portland cement and reinforced with random distribution of 2 percent coir fibre and admixed with 10 percent fly ash was roughly one and half to two times that of plain marginal soil.

The effect of arbuscular mycorrhizae inoculation on growth and yield of red chili on the highland andisol soil

One effort to improve soil fertility and plant productivity is through the inoculation of arbuscular mycorrhizae. Mycorrhizae plays a role in increasing the absorption of phosphorus elements in the soil. The study aimed to determine the effect of the inoculation of arbuscular mycorrhizae on increasing the growth and production of chili. The experiment was carried out in the highlands of West Bandung in 2017-2018. The experimental design used was a randomized completely block design (RCBD) with 5 treatments and 5 replications. The treatments consisted of control, 2 kg/m2 mycorrhizae in the nursery, 4 kg/m2 mycorrhizae in the nursery, 10 g/plant mycorrhizae at transplanting, and 20 g/plant mycorrhizae at transplanting. The mycorrhizae used was Glomus sp. in the form of inoculum (soil as a carrier). Variables observed included soil chemical properties, degree of root infection, vegetative growth, and yield of chili. Data were analyzed using analysis of variance (anova) and continued with Tukey’s Honestly Significantly Difference (Tukey’s HSD) test at 5% significancy level. The results showed that the inoculation of mycorrhizae to andisol on low P soils increased soil P availability, degree of root infection, vegetative growth, and red chili production, but high doses hurt chili yields. The inoculation of mycorrhizae doses of 2 kg/m2 in the nursery and 10 g/plant at transplanting can increase red chili production by 13.19% and 15.59%. To see the effectiveness of mycorrhizae more clearly, it is suggested to test mycorrhizae on chili in the dry season and on marginal soils.

Variations in strength and stiffness of cement-stabilized reclaimed asphalt pavement and marginal lateritic soil blends in tropical climate

This article investigated the effects of temperature on the variations in strength and stiffness of cement-stabilized reclaimed asphalt pavement (RAP) and marginal lateritic soil (MLS) as a sustainable bound base course of flexible pavement. A site investigation to assess the temperature profile of highway pavement in the northeast of Thailand was conducted to find the temperature variation of pavement structure in tropical country. Laboratory tests including unconfined compressive strength (UCS), modulus of elasticity (E50), and indirect tensile strength (ITS) tests were conducted on cement-stabilized RAP and MLS blends at varying mix proportions and temperatures. It is evident that the temperature significantly affects the strength and stiffness of specimens containing RAP due to the presence of bitumen covering the RAP aggregate. The additional MLS and cement can reduce the viscoelasticity of RAP aggregate. The strength reduction due to the temperature is characteristic of the RAP mixtures with MLS and cement. The normalized relationships of UCS and temperature and the empirical correlations between E50 and ITS versus UCS were presented. This set of relationships is a valuable tool for the mix design of cement-stabilized RAP and MLS blends as a bound base course in tropical countries.