Soil Chemical Properties Research Articles

Impact of fertility levels and rice genotypes on yield, quality, and chemical properties of soil under tarai region of Uttarakhand

A field experiment was conducted during kharif season of 2019 at Crop Research Centre of G.B. Pant University of Agriculture and Technology, Pantnagar (Uttarakhand) for evaluation of six rice genotypes (IET-27263, IET-26418, IET-26420, NDR-359, PD-19 and PD-26) under varying fertility levels (Control, 100% RDF, 150% RDF). Treatments were tested in Split Plot Design with three replications keeping fertilizer levels in main plots and genotypes in sub plots. Application of fertilizer at 150% RDF resulted in significantly higher grain and straw yield over all other fertilizer levels. The rice genotype IET-27263 produced highest grain, straw and biological yield over other genotypes. Similarly, total nitrogen, phosphorus and potassium content and uptake were also found to be increased significantly up to 150% RDF. Similarly, maximum uptake of N and K in grain and straw was also recorded in genotype IET-27263. It can be concluded that application of fertilizers at higher dose up to 150% RDF is essential for obtaining higher yield of rice. The new rice genotype IET27263 was found superior to all other tested genotypes.

Changes in the soil microbial community 5 years after the application of sewage sludge biochar to soils cultivated with corn

AbstractBackgroundSewage sludge biochar has been widely used in agriculture for various purposes; however, knowledge about its residual effect on the soil microbial community is limited.AimsThis study aimed to evaluate changes in the microbial community 5 years after the application of sewage sludge biochar.MethodsBiochar was produced from sewage sludge obtained at a wastewater treatment pyrolyzed at 300°C (Biochar300) and 500°C (Biochar500). Both biochar treatments were applied in corn fields for two growing seasons (2014/2015; 2015/2016). Biochar was not applied from the third (2016/2017) to the seventh (2020/2021) growing season to assess the residual effect. Soil samples were collected after harvesting in 2020/2021 growing season, therefore in the fifth year subject to the residual effects of biochar. The microbial community was evaluated by accessing bacterial and fungal groups using DNA techniques. Amplicon sequencing analysis was performed with the samples by Illumina MiSeq 250 bp.ResultsAt genus level, the Lachnospira, Faecalibacterium, Bacteroides, Epulopiscium, and Parabacteroides were affected by Biochar500. Furthermore, at upper levels of taxonomy, this biochar treatment increased the relative abundance of bacterial classes Clostridiaceae and Bacteroidia and the fungal families Chaetomiaceae and Aspergillaceae. Concerning the relationship between microbial community and soil chemical properties, soil phosphorus (P) and calcium (Ca) were significantly affected by biochar treatments within the bacterial community; the fungal ones affected significantly soil P and potential acidity (H + Al).ConclusionsEven under the residual effect of 5 years, the application of biochar altered the microbial community on corn plantation, especially concerning on the richness and the abundance of some groups. Biochar500 was the most responsive among the treatments.

Variation in Leaf Functional Traits of Populus laurifolia Ldb and Ulmus pumila L. Across Five Contrasting Urban Sites in Ulaanbaatar, Mongolia.

Amid urbanization, studying leaf functional traits of woody plants in urban environments is essential for understanding how urban green spaces function and how they can be effectively managed sustainably. In this study, we investigated the effects of different growing conditions on the morpho-physiological traits of Populus laurifolia and Ulmus pumila across five contrasting urban sites. The leaf area (LA), leaf length (LL), leaf width (LW), leaf biomass (LB), specific leaf area (SLA), leaf chlorophyll concentration, chlorophyll fluorescence parameters, leaf water potential at predawn (Ψpd) and midday (Ψmd), leaf performance index (PIabs), and phenotypic plasticity index (PPI) were compared across five contrasting urban sites. The soil chemical and physical properties were also compared between sites. There were significant differences in soil physicochemical characteristics between sites. We found significant effects of site on most of the morpho-physiological traits measured, except for Ψmd. The leaf chlorophyll concentration of P. laurifolia and U. pumila varied significantly between sites. The Ψpd was significantly different between years and sites. In U. pumila, the mean PPI for morphological traits (0.20) was lower than that for physiological traits (0.21). In conclusion, we revealed significant variations in the morpho-physiological traits of P. laurifolia and U. pumila across the five urban sites. Hence, long-term, large-scale studies are recommended to examine how diverse species respond to different urban growing conditions and to include other ecologically important plant traits for a better understanding of urban trees in a changing environment.

Effects of understory intercropping with salt-tolerant legumes on soil organic carbon pool in coastal saline-alkali land

Phytoremediation through understory intercropping with salt-tolerant legumes (forest-green manure composite patterns) efficiently and sustainably enhances saline-alkali soils, while significantly improving the stability of monoculture forest ecosystems and the efficacy of soil upgrades. However, exactly how forest-green manure patterns regulate the dynamics of the soil organic carbon (SOC) pool and related mechanisms remain unclear. For this study, a pure forest was used as the control, and three leguminous herbaceous plants (M. sativa, S. cannabina, and C. pallida) were intercropped under two forest stand types (T. hybrid ‘Zhongshanshan’ and C. illinoensis). The variable characteristics and control factors of SOC and its components under different patterns were elucidated by analyzing the soil physical and chemical properties, enzyme activities, and microbial communities. The results revealed that the composite pattern improved soil salinization and increased the activities of β-1,4-glucosidase, polyphenol oxidase, peroxidase (PER), invertase (INV), and urease, as well as the carbon pool management index and the proportion of active organic carbon. At the T. hybrid ‘Zhongshanshan’ experimental site, planting M. sativa effectively increased the total carbon (TC) content. The ammonium nitrogen, soil moisture content, total phosphorus, alkaline phosphatase, PER, and polyphenol oxidase were the primary driving factors that affected the SOC pool. At the C. illinoensis experimental site, S. cannabina planting was observed to increase the TC content, with the TC, exchangeable Na+, β-1,4-N-acetylglucosaminidase, and INV being the main driving factors that impacted the SOC pool. The composite pattern can indirectly influence the SOC pool by altering the soil properties to regulate the microbial community. Further, it was found that soil inorganic carbon (SIC) was the main contributor to increasing the soil carbon pool following the short-term planting of legumes; thus, there may have been a transfer process that occurred from the SOC to SIC. Our study suggests that the forest-green manure pattern has more positive effects on improving soil quality and the carbon pool in saline-alkali land.

Enhancing Agroecology in Pepper (Piper nigrum L.) Cultivation with Centrosema pubescens Ground Cover: A Study from Central Bangka, Indonesia

<p>Pepper cultivation in Bangka Island primarily takes place on sandy land. Legume cover crops, such as <em>Centrosema pubescens</em>, which has been widely used as a ground cover, are anticipated to improve land quality by maintaining soil temperature and humidity, increasing soil organic carbon content, increasing soil porosity, and improving soil fertility. This research aims to analyze the agroecosystem of pepper plants, by comparing the use of the cover plant <em>C. pubescens</em> as a soil treatment and the absence of using these cover plants as a control. The research was conducted in farmers’ pepper gardens in Perlang Village, Central Bangka Regency, Bangka Belitung Province. The research employed a randomized block design, with <em>C. pubescens</em> and natural vegetation as treatments, each replicated 3 times. The variables measured were soil temperature and humidity; abundance of microorganisms; weed density, frequency, and dominance; chlorophyll a, chlorophyll b, and anthocyanin content of pepper leaves; photosynthesis rate; transpiration rate; stomatal conductance; soil chemical and physical properties. The results showed that <em>C. pubescens</em> as ground cover could reduce the dominance of the <em>Bidens pilosa</em> weed (relative dominance of 36.16%) but led to an increase in the dominance of <em>Chromolaena odorata</em> (relative dominance of 38.7%). <em>C</em>.<em> pubescens</em> ground cover could also maintain stable soil temperature and moisture, and increase P, K, Ca, and Mg soil content by 100%, 100%, 43.6%, and 48.3%, respectively. Furthermore, pepper plants grown with <em>C. pubescens</em> exhibited 25%, 23.7%, and 16% higher chlorophyll a, total chlorophyll, and carotenoid content, respectively, compared to those grown without the cover crop.</p>

Depth Wise Distribution of Soil Physico-Chemical Properties and Nutrients Across a Toposequence Located at KVK Farm, Sakhigopal, Odisha, India

This study aims to identify soil-related constraints for crop production and provide insights for soil management by analyzing soil profiles across different topographic positions (upland, medium land, and lowland) at KVK farm, Sakhigopal, Puri located in the East and Southeastern Coastal Plain Agro-Climatic Zone of Odisha. The profiles were evaluated for key physico-chemical properties and nutrient contents, revealing significant variations influenced by topography. The results showed that the soil's physical and chemical properties and available nutrient status showed distinct variations among the pedons. Among soil physical properties, the sand percentage, bulk density, and particle density increased with soil depth. Whereas, the clay percentage, total porosity, and water-holding capacity decreased with soil depth. Soil pH ranged from 6.32 to 7.50 and the electrical conductivity was recorded below 1 dSm-1. The organic carbon content ranged from 8.6 to 10.3 g kg-1. In general, soil pH, base saturation, and exchangeable cations increased with soil depth. On the other hand, soil organic carbon content and exchangeable acidity decreased with soil depth. Available nitrogen, phosphorus, potassium, and sulphur contents decreased with soil depth. However, in general, their concentrations increased along the slope (towards low land), which may be attributed to increased levels of organic carbon and clay contents in the lower topographic positions owing to high moisture content and higher cropping intensity. The findings of this study provide valuable insights regarding soil property characterisation across a transect for sustainable land use planning.

Effects of mulch films with different thicknesses on the microbial community of tobacco rhizosphere soil in Yunnan laterite.

The mulch film (MF) management model of the agricultural field affects the physical and chemical properties of soil (PCPS) and the structure of the microorganism community; however, studies on the relationship between the rhizosphere microorganism community structure and the thickness of MF are still limited. To understand the interactions among the MF thickness, PCPS, and rhizosphere microorganism, a study was conducted by using an integrated metagenomic strategy, where tobacco rhizosphere soil was treated with four commonly representative and used thicknesses of MFs (0.004, 0.006, 0.008, and 0.010 mm) in Yunnan laterite. The results showed that agronomic traits such as the tobacco plant height (TPH), leaf number (LN), fresh leaf weight (FLW), and dry leaf weight (DLW) were significantly (p < 0.01) improved in the field mulched with the thickest film (0.010 mm) compared with the exposed field (CK), and there was a 6.81 and 5.54% increase in the FLW and TPH, separately. The correlation analyses revealed a significant positive correlation of the MF thickness with the soil water content (SWC), soil organic matter (SOM), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), and available phosphorus (AP; all p < 0.01), while the MF thickness was negatively correlated with the soil temperature (ST; p < 0.01). In addition, the community structure of the rhizosphere soil bacteria was significantly changed overall by the MF thickness, which also interfered with the function of the rhizosphere soil bacteria. The correlation analyses also showed that the abundance of Bradyrhizobium and Nitrospira was positively correlated with the MF thickness, while the abundance of Sphinsinomonas and Massilia was negatively correlated with it. This indicated that with the increase of the MF thickness, the ability of the rhizosphere soil to utilize N and remove harmful molecules was strengthened, while the capacity of the rhizosphere soil to degrade pollutants was greatly reduced. These findings provide additional insights into the potential risks of the application of different thicknesses of MFs, particularly concerning the PCPS and soil microbial communities.

Fire Impacts on Soil Properties and Implications for Sustainability in Rotational Shifting Cultivation: A Review

Fire, a prevalent land management tool in rotational shifting cultivation (RSC), has long been debated for its immediate disruption of surface soil, vegetation, and microbial communities. While low-intensity and short-duration slash-and-burn techniques are considered beneficial for overall soil function, the dual nature of fire’s impact warrants a comprehensive exploration. This review examines both the beneficial and detrimental effects of fire on soil properties within the context of RSC. We highlight that research on soil microbial composition, carbon, and nitrogen dynamics following fire events in RSC is gaining momentum. After fires, soil typically shows decreases in porosity, clay content, aggregation, and cation exchange capacity, while sand content, pH, available phosphorus, and organic nitrogen tend to increase. There remains ongoing debate regarding the effects on bulk density, silt content, electrical conductivity, organic carbon, total nitrogen, and exchangeable ions (K+, Ca2+, Mg2+). Certain bacterial diversity often increases, while fungal communities tend to decline during post-fire recovery, influenced by the soil chemical properties. Soil erosion is a major concern because fire-altered soil structures heighten erosion risks, underscoring the need for sustainable post-fire soil management strategies. Future research directions are proposed, including the use of advanced technologies like remote sensing, UAVs, and soil sensors to monitor fire impacts, as well as socio-economic studies to balance traditional practices with modern sustainability goals. This review aims to inform sustainable land management practices that balance agricultural productivity with ecological health in RSC systems.

Effects of soil amendments and coverings on the kenaf yield and soil physicochemical properties in saline-alkali land

In order to investigate the effects of various treatments on the growth of kenaf in saline soil, this study employed a comprehensive experimental design incorporating a dual approach of soil amendment and mulching techniques. Soil treatment of saline and alkaline land, as well as biological material mulching treatment after sowing kenaf, were conducted. The growth dynamics of kenaf were assessed before the mid-term investigation, and the harvest period was examined. Soil physicochemical properties were measured and analysed at different periods. The results show that in the analysis of red sesame yield traits, the differences mainly appeared between soil treatments. There is no significant difference between the different mulching treatments within each soil treatment. In the mid-term study, significant differences were observed in kenaf plant height. Plant height was the most affected by soil conditioners, while other yield traits did not show significant variations. During harvest, only stem thickness and dry weight of a single plant did not show significant differences, whereas other yield traits did. The application of soil conditioners resulted in a 58.15% increase in dry hull yield compared to organic fertilizers and a 22.66% increase compared to regular fertilizers. Soil conditioners also led to higher levels of effective phosphorus, quick-acting potassium, organic matter, and total nitrogen throughout the kenaf growth period compared to organic and regular fertilizers. This is beneficial for enhancing soil quality and reducing soil alkalinity. Combined with the results of kenaf yield and soil physical and chemical properties analysis, it has been proven that the application of soil conditioner has the best effect, followed by the application of compound fertilizer, with organic fertilizer treatment being the least effective.

Characteristics of soil pore structure response to electric field strength and their effects on Cr(VI) removal from a historically chromium-contaminated soil

The characteristics of soil pore structure response to electric field strength and their effects on the migration of hexavalent chromium during electrokinetic remediation remain unclear. This paper investigates the effects of soil actual voltage and pore redistribution on hexavalent chromium removal under various voltage gradients during electrokinetic remediation. The electric field across the soil was the dominant factor that affected the soil properties, pore structure, and transportation of hexavalent chromium. The removal efficiency of dissolved hexavalent chromium was significantly enhanced from 36.1 % to 80.5 % as the theoretical voltage gradients increased from 0.5 V·cm−1 to 3 V·cm−1 due to the highest voltage proportion (52.7 %) of the soil chamber at 3 V·cm−1, while it only increased to 82.0 % at 4 V·cm−1. The optimal actual electric field strength of 1.00–1.50 V·cm−1 across the soil matrix facilitated the efficient electromigration of hexavalent chromium. The electric field force exerted a direct (0.70) or indirect action intensity (1.55) on soil pore structure by altering soil chemical properties. Soil mesopores and ultra-micropores transformed into micropores through collapsing, shrinking, ion migration, weakening electrostatic repulsion, and enhancing adhesive bonding among particles with increasing electric field. The distribution and structure of soil pores were more homogenous under optimal electric field conditions, thereby improving the migration path of hexavalent chromium. Soil mesopores facilitated hexavalent chromium removal and the formed micropores were opposite. These findings have significant scientific and practical implications for applying the in-situ electrokinetic techniques in the remediation of metal-contaminated soils.

Assessment of soil chemical characteristics in the context of Bangladesh: A comprehensive review

This study presents a thorough examination of the chemical properties inherent to soil, with a focus on the unique context of Bangladesh. Soil functions are intricately linked to its chemical composition, which plays a vital role in determining agricultural productivity and ecological vitality. The soil within Bangladesh's geographical boundaries is characterized by its richness and fertility, contributing significantly to its agricultural output and overall ecosystem health. By delving into the chemical properties of Bangladeshi soil, this review aims to enhance our understanding of this dynamic ecosystem. Insights gained from this exploration can shed light on factors influencing soil fertility, nutrient availability, and overall ecosystem health, thereby informing strategies for sustainable land management and agricultural practices in Bangladesh and beyond.

Effect of Potassium and Zinc on Soil Properties and Fraction of Potassium and Zinc in Soil

A field experiment was carried out on Agronomy Farm, B. A. College of Agriculture, Anand Agricultural University, Anand during rabi season of the year 2020-21. The experiment comprising nine treatment combinations consisted of three levels of potassium (0, 20 and 40 kg/ha) and three levels of zinc (0, 2.5 and 5.0 kg/ha). These treatments were evaluated in Randomized Block Design (factorial) with four replications. The soil of the experimental plot was loamy sand in texture, alkaline in reaction, low in organic carbon and available nitrogen, medium in available phosphorus, potassium and zinc. Results of the experiment revealed that the available K2O in soil was significantly increased due to application of 40 kg K2O/ha (K2) and was found to be at par with application of 20 kg K2O/ha (K1). All other chemical properties of soil (pH, EC, organic carbon, available N, P2O5, S, Fe, Mn, Zn and Cu) were not differ significantly due to application of different levels of potassium. Levels of zinc also failed to produce its significant effect on chemical properties of soil except available Zn in soil as it was significantly increased with the treatment of Z2 (5.0 kg Zn/ha) than control but was found to be at par with treatment Z1 (2.5 kg Zn/ha). Moreover, no any chemical property of soil differ due to the interaction of different levels of potassium and zinc. The water soluble K and exchangeable K fractions in soil significantly increased with the treatment of K2 (40 kg K2O/ha) otherwise non-exchangeable K, total K and different zinc fractions in soil did not differ significantly by the different levels of potassium. Different potassium fractions and total Zn fraction in soil were found to be non-significant under the different zinc levels but all the zinc fractions in soil (water soluble plus exchangeable Zn, carbonate bound Zn, Fe/Mn oxide bound Zn, organically bound Zn and residual Zn) significantly increased with the treatment of Z2 (5.0 kg Zn/ha) and was remained at par with treatment Z1 (2.5 kg Zn/ha). The interaction between potassium and zinc failed to influence significantly on potassium and zinc factions in soil.

Effects of the combination of biochar and organic fertilizer on soil properties and agronomic attributes of soybean (Glycine max L.)

This research aimed to investigate the impacts of a combination of rice husk biochar and organic fertilizer on the physical and chemical properties of soil, the population of soil bacteria, the relative chlorophyll content of leaves, the development of soybean root nodules, and yield components under strongly acid soil conditions. A greenhouse and pot experiment was designed using a randomize complete block design with factorial 2 × 3 treatments and three replications. The experimental treatments comprised two rates of biochar (35 and 70 g/pot) and three rates of organic fertilizer (70, 105, and 140 g/pot). After 100 days of amendment of strongly acidic soils, the results showed that application of treatments B35F70 and B70F140 increased soil pH by 16.80% compared to the control group (CK). On the other hand, treatments B35F140 and B70F105 resulted in an increase of soil electrical conductivity by 66.67% compared to CK. In addition, after 100 days of amendment with treatments B35F105, B35F105, B35F140, B70F105, B70F70, B70F70, and B35F140, organic matter, available phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn), organic matter, available phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn), significantly increased when compared to the control group (CK). Treatment B35F140 increased relative leaf chlorophyll content and soybean seed weight per plant by 60.76% and 100.56%, respectively when compared to the CK. Furthermore, treatment B35F70 produced 125% more root nodules than CK. Moreover, each amended strongly acid soil resulted with a significant upsurge in total soil bacteria compared to the CK. Overall, statistics proved that a combination of biochar and organic fertilizer improved soil properties and soybean agronomic attributes.

Unlocking higher yields in Urochloa brizantha: the role of basalt powder in enhancing soil nutrient availability

This study investigates the effect of basalt powder on soil fertility through changes in its chemical characteristics and the response of Urochloa brizantha to different application doses. The experiment was conducted in a greenhouse using two distinct soil types: Oxisol (OX) and Typic Quartzipsamment (TQ). Basalt powder dosages were determined based on the calcium levels required to adjust calcium contents in each soil (Ca2+) to recommended levels for the U. brizantha,ranging from 0 to 4 times the recommended amount. After 170 days of incubation, soil samples were collected for analysis to evaluate soil attributes. U. brizantha was then planted to assess the efficiency of basalt powder, which was harvested at 40 days after sowing (first cut) and 70 days after sowing (second cut). The accumulation of nutrients and shoot dry mass (SDM) production were subsequently measured. The findings revealed that applying the highest dose of basalt powder (96 Mg ha−1) substantially elevated pH, and increased concentrations of phosphorus (P), potassium (K+), calcium (Ca2+), magnesium (Mg2+), copper (Cu), boron (B), and silicon (Si) in Oxisol (OX), while decreasing aluminum (Al3+) contents in the same soil. Furthermore, an average increase in the SDM of both U. brizantha harvests was observed, with a 6% increase in TQ and a 27% increase in OX. Additionally, an increase in the accumulation of P, K, Ca, Mg, and sulphur (S) in the shoot dry mass of the plants was observed with the basalt powder doses. These findings suggest that basalt powder has the potential to be an environmentally friendly alternative for soil fertilization, with positive impacts on soil chemical attributes and plant growth and nutrition.

Identification of land fertility and farmer income after an earthquake natural disaster

Liquefaction is a phenomenon where saturated sand and silt take on the characteristics of a liquid during the intense shaking of an earthquake. It takes place when a quake has increased water pressure in saturated soil and made particles in the soil lose contact with each other, making the soil, particularly sandy soil, act like a liquid. On September 28, 2018, an earthquake was occurred which caused liquefaction and a tsunami in Central Sulawesi, Indonesia. This incident triggered a new phenomenon, namely liquefaction in several residential areas in Palu City, especially in the Balaroa and Petobo areas. The liquefaction phenomenon in Petobo Village caused changes in the shape of the land surface. The changes that occurred had an impact on decreasing soil fertility levels in the area along with low crop production and decreased farmer incomes. Soil fertility is a quality value of the soil's ability to provide nutrients for growth. This research aims to determine the level of fertility of agricultural land and the amount of farmer income as well as the best efforts to overcome changes in agricultural land after natural disasters. This research used a descriptive method with a population of all farmers living in the Petobo area affected by the earthquake and liquefaction. There were 25 informants who were determined using a purposive sampling technique. Soil samples were analyzed at the Soil Science laboratory, Faculty of Agriculture, Tadulako University, Palu. The method used in this study is a direct survey method in the field, then continued soil sampling at several points according to the coordinate points carried out by purposive sampling techniques. The status of soil chemical properties at 4 sample points affected by liquefaction and 2 sample point not affected by liquefaction in Petobo Village, which classified as very low to very high. Areas affected by liquefaction had neutral to slightly alkaline soil pH content, very low to low C-organic content, very low N-total content, very high P-total content, low K-total content, and have medium to high CEC content. Meanwhile, areas that are not affected by liquefaction had neutral soil pH content, very low to low C-organic content, very low N-total content, very high P-total content, low K-total content, and have medium to high CEC. The low level of soil fertility in this area means that crop production is also low. Changes in the amount of income experienced by affected farmers who initially had around 77.26 USD- 186.71 USD/month declined to 61.16 USD-77.26/month. This is due to changes in the polarization of farmers' work. Actions that can be implemented to increase soil fertility are correct soil management, use of organic fertilizers such as compost, manure, harvest residues such as (legume plant stover, rice straw) and the addition of chemical fertilizers according to the dosage.

SPATIAL VARIABILITY OF PRODUCTION AND BROMATOLOGICAL COMPOSITION OF Brachiaria AND Panicum ACCORDING TO THE SOIL CHEMICAL ATTRIBUTES IN A SILVIPASTORAL SYSTEM WITH EUCALYPTUS

The variability of the soil chemical attributes in an area where woody crops are integrated with forage is quite complex, so it is important to understand the distribution of these soil attributes and their correlation with the forage yield. This study aimed to analyze the spatial variability of the production and bromatological composition of Brachiaria and Panicum forage species according to the soil chemical attributes when cultivated in a silvopastoral system integrated with eucalyptus to optimize the forage yield and nutritional quality of the forage in this multiple-use system. The study was conducted in the municipality of Ribas do Rio Pardo (MS) in the 2011/2012 crop season, where linear and spatial correlations were analyzed between attributes of eucalyptus, forage plants, and the chemical attributes of a Neossolo Quartzarênico (pH, organic matter (OM) and organic carbon (OC) contents, and carbon stock (CS)) at two soil layers: 0.00-0.10 and 0.10-0.20 m. A geostatistical grid with 72 sample points was used. Spatially, eucalyptus height can be estimated by cokriging with OM, and cellulose by cokriging with pH. OM contents above 6 g cm-3 indicated sites with the highest eucalyptus heights. On the other hand, pH values below 4.3 indicated sites with the highest cellulose content for the forage plants. Using geostatistics is technically feasible for creating specific management zones in the eucalyptus forage silvopastoral system.

Study of soil heterotrophic respiration as a function of soil moisture under different land covers

The relationship between soil heterotrophic respiration (Rh) and soil moisture has been often studied using disturbed soil samples and simple gravimetric and volumetric soil moisture indicators. The objective of this study was to investigate the relationship between Rh and soil moisture in terms of water-filled porosity (WFP), matric potential (Ψm), and relative soil gas diffusivity (Dp/Do) using undisturbed soil cores obtained under different land covers. Soil CO2 efflux, WFP, and Ψm were measured in undisturbed soil samples (250 cm3) collected in the 0–5 cm soil layer (without any vegetation or living roots) under laboratory conditions by combining a CO2 gas analyzer, a scale, and precision mini-tensiometers. For each site and land cover, we also measured soil chemical properties, soil physical properties, and soil microbial composition using phospholipid fatty acid analysis. Grassland soils had the largest total microbial biomass (6275 ng g−1), followed by soils from riparian (5327 ng g−1), and cropland (2745 ng g−1) sites. Bacteria were the dominant group representing 46% (SD = 5%) of the total microbial biomass across all sites and land covers. Maximum Rh was 1.88 (SD = 0.40) μmol CO2 m−2 s−1 in grassland, 1.64 (SD = 0.82) μmol CO2 m−2 s−1 in riparian, and 0.94 (SD = 0.56) μmol CO2 m−2 s−1 in cropland soils. Considering all land cover and soil types, our observations revealed that peak Rh occurred at mean WFP = 0.81 ,Ψm = −6 kPa, and Dp/Do = 0.003. Thus, we recommend avoiding the traditional field capacity definition of −33 kPa for representing peak microbial activity. Water-filled porosity was a more consistent predictor of Rh than Ψm or Dp/Do across soils with contrasting organic matter content, total microbial biomass, soil texture, and soil structure.

Enhancing pyromorphite formation through hydroxyapatite application in lead-contaminated, water-unsaturated soils: influence of low percolation velocity and high soil porosity

Abstract Purpose Chemical immobilization using hydroxyapatite (HAP) is a cost effective and environmentally sound strategy for remediating lead-contaminated soils, such as shooting range soils. Understanding the combined impact of soil chemical and physical properties on enhancing the formation of pyromorphite, a lead-insoluble phase, is crucial for mitigating environmental risks associate with contaminated soil. This study aimed to elucidate the relationship between percolation velocity and lead leaching as well as pyromorphite transformation to optimize pyromorphite formation in water-unsaturated soils. Methods Two up-flow suction percolation tests were performed: one varying percolation velocity with soil porosity achieved by incorporating clay minerals, and the other varying percolation velocity while keeping soil porosity constant. Results Application of HAP substantially suppressed lead leaching in both percolation tests. Enhanced pyromorphite formation was observed with higher percolation velocities relative to soil porosity. Pyromorphite formation was more pronounced at lower percolation velocities compared to higher velocities at equivalent soil porosity level. The percentages of lead formed as pyromorphite in HAP-treated soil were higher than those of lead leached in non-HAP-treated soil among the lower percolation velocities. Conclusions This study provides experimental evidence indicating pyromorphite formation is favored in soils with lower percolation velocities and higher soil porosities. Therefore, considering both soil chemical and physical properties is essential for understanding immobilization mechanisms in contaminated soils.

Studying the effect of irrigation water quality (fresh water, treated water and wastewater) on some soil physical and chemical proper-ties and the protein content in the paulownia leaves.

Samples of soil irrigated with three types of water: Fresh water (F), wastewater (W), fresh water and wastewater (F1W1, alternative irrigation) were collected at two depths (0-15 cm and 15-30 cm) for two consecutive years. The bulk density, true density, soil total porosity, electrical conductivity, pH, percentage of organic matter, and concentration of phosphorus and potassium were measured. In addition, the length and circumference of paulownia tree trunk were measured, and the protein content of dry and green leaves was estimated. The results showed the differences in the apparent density values, as wastewater irrigation decreases the apparent density and increased the soil total porosity. The results also indicated that there were significant differences in the soil PH between the three treatments, as treated water irrigation decreased the pH and insignificantly increased the soil electrical conductivity. However, there were significant differences when irrigating with wastewater, as the electrical conductivity and organic matter content increased in the soil irrigated with wastewater compared to soil irrigated with fresh water at two depths (0-15cm and 15-30cm). Moreover, the concentrations of phosphorus and potassium increased in the soil irrigated with wastewater and treated water compared to fresh water. Furthermore, there were significant differences in the height of paulownia tree and its trunk circumference when irrigating with treated water compared to wastewater and fresh water. As for the protein content in paulownia leaves, it was observed that there were significant differences when irrigating with wastewater compared to treated water and fresh water. There was high protein content in the dry and green leaves when irrigating with the three types of water, but the highest protein content was for wastewater irrigation.

Fertilized soils enhance the efficiency of phytoremediation by tropical grasses in cadmium-contaminated soils

The effectiveness of phytoremediation in Cd-contaminated soils is crucial for enhancing nutrient availability and plant tolerance to Cd. We simulated soil contamination with varying textures and fertilization conditions. Two experiments were conducted: one without liming and fertilization and another with soil fertilization for grasses. The soil types used were Oxisol and Entisol, and the grasses tested were Megathyrsus maximus and Urochloa brizantha at three Cd levels: 0 mg kg−1 (Control), 2 mg kg−1 (Low), and 12 mg kg−1 (High). Soil amendments and fertilization did not significantly change Cd availability. Soil chemical attributes were unaffected by Cd contamination but were influenced by fertilization, which kept the pH below optimal levels. Cd availability was higher in more contaminated soils, with Entisol showing greater concentrations than Oxisol. Dry matter production of the grasses decreased with higher contamination, with U. brizantha being more productive than M. maximus in fertilized soils. Cd accumulation was higher in highly contaminated soils, particularly for U. brizantha. The bioconcentration factor was higher in Entisol, while the translocation factor exceeded 1.0 only for M. maximus in low-contamination Oxisol. Fertilization can mitigate Cd contamination effects, with U. brizantha showing greater tolerance and accumulation capacity in fertilized soils.