Sulfate Soils Research Articles

Establishing critical limits of sulphur for groundnut (Arachis hypogaea)

Sulphur is essential for growth and development of groundnut (Arachis hypogaea L.). Deficiency of S is widespread in soils of India, and is becoming a major concern for the quality and yield of groundnut crop. Therefore, a study was conducted to investigate the response of groundnut to S application in alluvial Inceptisols of West Bengal with four levels of S, i.e. 0, 15, 30 and 45 kg/ha. The critical limits of Sulphur in soil and plant for deficiency, adequacy and toxicity were determined from Bray percent yield (BPY). The amount of CaCl2 extractable S in soils varied from11.90–29.17 mg/kg while the critical level for deficiency of S in groundnut was graphically 18.6 mg/kg and statistically 19.58 mg/kg in soils. Application of S increased groundnut yield significantly, concentration of S in plant and its uptake by groundnut parts. The critical limit was determined to be 3.0 g/kg for groundnut plants and 4.42 g/ kg for groundnut nuts at harvest.

Feasibility of bioleaching of heavy metals from sediment with indigenous bacteria using agricultural sulfur soil conditioners

Sediment bioleaching using a sulfur substrate is a promising approach to the removal of heavy metals. Compared with commercial sulfur powder used as the sulfur substrate, agricultural sulfur soil conditioners may reduce secondary pollution and facilitate the reuse of sediment. This study explored the bioleaching effect of three agricultural sulfur soil conditioners, including sulfur-coated urea, bentonite sulfur, and bio-sulfur, and the bioleaching potential of the indigenous sediment bacteria. The results showed that the sulfur-coated urea had a comparable bioleaching effect with sulfur powder (Ni 35.35%, Cu 74.27%, Zn 69.92%) and the highest maximum bioleaching rate because of the additional nitrogen. The bentonite sulfur leached the least but increased the proportion of the residual state due to its adsorption of heavy metal. Similar changes to the microbial flora structure and bioleaching mechanism were found with the use of sulfur powder, sulfur-coated urea, and bentonite sulfur as the bioleaching substrate. There was no significant difference between the indigenous bacteria and the sludge-enriched bacteria in the bioleaching effect except for bio-sulfur, which only performed well with the sludge-enriched bacteria. In the absence of inoculum, the bio-sulfur hindered the bioleaching process due to high levels of organic matter. This study provides insights into the practical application of bioleaching heavy metal removal technology from the perspective of sulfur substrate selection.

The oxygen and sulfur isotopic compositions of soluble sulfate in the needles of Pinus massoniana Lamb.: Source discrimination and contribution estimation

In order to identify the sources of sulfate in plant leaves, needles of Pinus massoniana Lamb. were collected from Guiyang (an area seriously affected by acid rain) and Yunnan areas (where acid rain barely occurred) in southwestern China to measure the isotopic compositions of the water-soluble sulfate (δ34SSO4 and δ18OSO4) and leaf water (δ18OH2O). Compared to atmospheric sulfate, all needle samples were quite depleted in 18O, indicating that sulfate in needles was rarely derived from atmospheric sulfate. The δ18OSO4 values in the needles (−5.3‰) were similar to those in the soil (−5.2‰) in the uncontaminated mountain area of Jinning, suggesting that sulfate in needles originated mainly from soil sulfate in barely SO2 pollution areas. However, the δ18OSO4 values in the needles were significantly more negative than that of soil in most areas with relatively severe SO2 pollution, and the δ18OSO4 values in the needles were positively correlated with the δ18OH2O values of leaf water, indicating that a substantial part of the sulfate in the needles might be derived from atmospheric SO2 oxidation in polluted areas. The estimated contributions of atmospheric SO2 oxidation to the sulfate in the needles increased significantly with increasing atmospheric SO2 and needle sulfate concentration. When the atmospheric SO2 concentrations were >30 μg m−3, the contributions of SO2 to needle sulfate were >50%. The δ18OSO4 values in needles decreased obviously with the increase of the distance from both the Steel Plant and the Power Plant, implying that part of needle sulfate likely to be derived from primary sulfate which generated in the industrial plant flues and secondary sulfate which generated in atmosphere.

Effects of Spartina alterniflora invasion in a seaward direction on variations of inorganic sulfur forms in marsh soils of the Minjiang River estuary, China

To explore the effects of Spartina alterniflora invasion in a seaward direction on variations of inorganic sulfur forms in marsh soils, the levels of inorganic sulfur forms (H2O-S, Adsorbed-S, HCl-Soluble-S and HCl-Volatile-S) were determined in bare flat (BF, before invasion), S. alterniflora marsh after seaward invasion for one year (SA') and S. alterniflora marsh after seaward invasion for three years (SA) in Shanyutan of the Minjiang River estuary with the method of space-for-time substitution. Results showed that the seaward invasion of S. alterniflora altered the stocks and distribution of inorganic sulfur form in marsh soils. Compared with BF, the contents of H2O-S, Adsorbed-S and HCl-Volatile-S in soils of SA increased by 52.6%, 78.2% and 21.0%, respectively, while that of HCl-Soluble-S decreased by 3.4%. In contrast, the levels of H2O-S, Adsorbed-S and HCl-Soluble-S in soils of SA' increased by 43.9%, 70.6% and 29.6%, respectively, whereas that of HCl-Volatile-S decreased by 11.6%. The contents of total inorganic sulfur (TIS) in soils of SA and SA' increased by 40.7% and 37.8%, while the stocks of TIS increased by 26.8% and 31.4%, respectively. The key factors affecting different forms of inorganic sulfur in marsh soils had changed due to the seaward invasion of S. alterniflora. In particular, the key factors affecting the variations of H2O-S contents changed from soil grain composition and bulk density in BF to soil organic matter in SA' and SA. The seaward invasion of S. alterniflora significantly increased the content of TIS in marsh soils, which was mainly contributed by H2O-S and Adsorbed-S. Thus, it was concluded that the seaward invasion of S. alterniflora significantly increased the supply capacity of available sulfur in marsh soils, which, to some extent, accelerated its seaward invasion.

Dactylis glomerata L. cultivation on mercury contaminated soil and its physiological response to granular sulphur aided phytostabilization

Most mercury (Hg) deposition in the environment results from anthropogenic inputs, Chlor-Alkali Plants (CAPs) particularly had a significant Hg impact on the environment at a regional scale. Exposure to mercury compounds resulting in various toxic effects for living organisms. The aim of this study was to investigate the capacity of granular sulphur (S) soil amendment and cultivation of Dactylis glomerata to decrease gaseous mercury emission to the atmosphere and mercury mobility in soils affected by CAP activity in the past. The effect of this approach on D. glomerata physiological status was also assessed (Hg concentration in biomass, chlorophyll a fluorescence, pigment contents and oxidative stress). Stabilization of mercury in soil and reduction of root and shoot concentration did not influence biomass production. Despite similar yields, photosynthetic efficiency was higher for plants grown in sulphur amended soil compared to unamended soil, particularly observed in phenomenological energy fluxes. Relative chlorophyll content was 30% lower for amended soil plants, however based on chlorophyll fluorescence data those were in high portion ineffective. Oxidative stress products and catalase activity did not differ significantly between experimental treatments. Sulphur amendment was a key factor for reduction of Hg mobility in soil (reduced by about 30%) while plant cover was significant for the reduction of Hg atmospheric emission (emissions were 2-times higher in sulphur amended soil without plant cover). Due to the very high concentration of Hg in soil (798.2 ± 7.3 mg kg−1), growth inhibition was consistent regardless of treatment, demonstrated in the overload Reactive Oxygen Species scavenging mechanism and similar biomass yields. This leads to the conclusion that Hg may have greater impact on Calvin-Benson cycle associated enzymes than on the light-dependent photosynthesis phase. Despite these limitations this approach may still decrease environmental risks by reducing Hg emission to the atmosphere and reducing groundwater contamination.

Chemo-Mechanical Interactions in the Ettringite Induced Expansion of Sulfate-Bearing Soils

Expansive sulfate-bearing soils are frequently encountered in transportation and construction practices. These soils are often treated with a lime or cement stabilizer to improve the relevant qualities. However, the reaction between sulfate and alumina in soils and calcium of lime or cement can lead to the formation of ettringite, an expansive sulfate mineral resulting in soil swelling or heaving. The underlying mechanisms often involve intricate interactions between chemical processes and mechanical responses. The present study explores a chemo–mechanical approach in an attempt to quantify several mechanisms potentially responsible for the volume expansion, including the geochemical formation of ettringite, crystallization pressure, and osmosis-induced swelling. The geochemical reaction leading to ettringite formation is examined with a specific focus on the circumstances under which it may lead to volume change. The crystallization pressure developed during the ettringite formation may also play a significant role in the soil expansion and is investigated in the present study based on thermodynamic formulations, and the resulting volume expansion is simulated. The osmosis-induced swelling is studied within the context of the chemo–mechanical framework, and its kinetics is also explored. Numerical simulations are performed in the present study to examine different scenarios driven by distinct predominant mechanisms. In particular, the interplay between ettringite formation and osmosis swelling as interpreted from some recently-reported experimental studies shows that these mechanisms can all contribute to the observed expansion processes, and overall, the modeling results are consistent with the experimental findings.

Available macronutrient status of soils in various cropping systems of Thotapalli irrigation project ayacut of North coastal Andhra Pradesh

Assessment of macronutrient status of soils under five major cropping systems namely, rainfed mango/cashew orchards, rainfed groundnut/mesta cropping, irrigated rice followed by pulses, irrigated rice followed by maize and irrigated sugarcane in Thotapalli irrigation project ayacut area of north coastal Andhra Pradesh was carried out. A total of 125 random soil samples were collected from five different cropping systems from five villages of five Tehsils (mandals) namely, Cheeprupalli, Therlam (both tehsils from Vizianagarm district), Ranasthalam, Regidiamadalavalasa and Laveru (from Srikakulam district). The results of the study revealed that the soil organic carbon (OC), available nitrogen (N), phosphorus (P), potassium (K) and sulphur (S) contents of the irrigated land was higher than adjacent rainfed upland, however the exchangeable calcium and magnesium were higher in rainfed uplands and relatively lower in irrigated cropping systems. Significant positive correlation was noticed between percent clay content with available N (r = 0.311**), available P2O5 (r = 0.232*), available K2O (r = 0.473**), available Sulphur (r = 0.249*), likewise organic carbon content also positively correlated with available N (r = 0.456**), available P2O5 (r = O.578**), available K2O (r = 0.211*) and available sulphur (r = 0.298*), while available phosphorous, was negatively correlated with soil pH, EC and CaCO3 contents. The variations in soil properties and nutrient status among cropping systems indicate need for employing integrated and soil test based nutrient management in sustainable manner.

Effect of short-term sulphate contamination on lime-stabilized expansive soil

ABSTRACT Lime stabilization is an age-old technique for controlling the swell-shrink characteristics of the expansive soil. However, the presence of sulphate in the expansive soils renders the lime stabilization ineffective due to the formation of detrimental compounds – ettringite and thaumasite. The formation of these detrimental compounds can be counteracted by treatment with low-calcium or non-calcium based stabilizers. However, there is a possibility of sulphate contamination post lime stabilization through external sources. Therefore, the present study brings out the effect of short-term sulphate contamination on lime-stabilized expansive soil using sodium sulphate solution. To achieve this objective, the lime-stabilized expansive soil was cured for 1, 7 and 28 days, and subsequently mixed with sulphate solutions of 5000–20,000 ppm concentration and allowed to equilibrate for 1 day. The experimental results showed that the sulphate contamination had a significant effect on the soil structure, physico-chemical and index properties of lime-stabilized soil. The mechanism governing the deterioration of the stabilized soil depended on the curing period of lime-stabilized soil prior to contamination with sulphate. Short-term sulphate contamination of lime-stabilized soil cured for 1 and 7 days resulted in highly flocculated structure, whereas the lime-stabilized soil cured for 28 days resulted in the formation of ettringite. This is evidenced with the aid of Scanning Electron Microscopy (SEM) images, X-ray diffraction (XRD) and Energy Dispersive X-Ray Analysis (EDAX). It can be concluded from this study that the ettringite formation occurs even after the formation of pozzolanic compounds in lime-stabilized soil.

Bioaugmentation of endosulfan contaminated soil in artificial bed treatment using selected fungal species

Pollutants when incorporated in the soil lead to adverse effect on soil quality. Bioaugmentation provides very attractive, eco-friendly, and economic solution to problems associated with hazardous pollutants. The present study conducted biodegradation potential of four fungal species namely; Cladosporium cladosporioides, Penicillium frequentans, Trametes hirsuta, and Trametes versicolor to degrade endosulfan in soil using artificial bed. Individual fungi as well as their consortium are able to degrade endosulfan in soil. Toxicological effect of endosulfan and its degradation products in soil fertility was also evaluated during study. To evaluate the toxicological effect of endosulfan and its degradation products in soil fertility, soil pH, total microbial population and the soil enzymes activity were also analyzed. At the end of 30 days of incubation period, maximum per cent degradation of endosulfan was observed in soil augmented with T. hirsuta (86.23%), followed by T. versicolor (67.35%) which was at par with fungal consortium (63.49%). Degradation of endosulfan in soil treated with C. cladosporioides and P. frequentans was 60.37% and 56.18%, respectively. In addition, degradation of endosulfan decreased in all treatments as its concentration increased in soil. All tested fungi degraded α-endosulfan more efficiently than β-endosulfan. At the end of experiment (after 30 days), maximum degradation of both isomers was recorded in soil augmented with T. hirsuta (α = 93.03 ± 2.86 and β = 79.42 ± 2.71%). Fungi which showed more endosulfan degradation also produced more endosulfan sulfate in soil. However, less endosulfan sulfate was recorded in T. hirsuta and T. versicolor, though they degraded endosulfan more efficiently. pH in natural soil (control) and abiotic control remain at par during the complete incubation period and ranged between 7.45 ± 0.03 to7.49 ± 0.01. In soil treated with T. hirsuta and T. versicolor, pH was decreased significantly to acidic range (6.44 ± 0.04 and 6.64 ± 0.01, respectively). In soil treated with fungal consortium, pH increased initially (7.57 ± 0.04), but later it was found to decrease (7.16 ± 0.03). Usually, after an initial toxic effect, mineralization of endosulfan leads to an increase in microbial populations and enzyme activities in bioaugmented soil, and the efficient fungi caused more pronounced increment.

Temporal availability of phosphorus and sulphur in acid Inceptisol as influenced by graded application of P and S under black gram (Vigna mungo L. Hepper) production

A pot culture experiment was conducted at School of Natural Resource Management, College of Post Graduate Studies in Agricultural Sciences, CAU, Umiam, Meghalaya to assess the temporal availability of phosphorus and sulphur in acid Inceptisol of Meghalaya as influenced by graded application of P and S under black gram (cv. SBC-47) production. The treatment consisted of four levels of P (20, 40, 60 and 80 mg P kg-1 soil) and four levels of S (10, 20, 30 and 40 mg S kg-1 soil). The experiment was laid out in factorial completely randomized design with three replications during kharif season of 2016. The experimental soil was deficient in available phosphorus (13.85 kg ha-1) and available sulphur (15.91 kg ha-1). The results revealed that combined application of P and S had significant effects on seed and stover yield of black gram. The optimum seed and stover yield were recorded with combined application of 60 mg kg-1 soil and 30 mg kg-1 soil, respectively which was statistically at par with combined application of 80 mg P kg-1 soil and 40 mg S kg-1 soil. The assessment of temporal availability of phosphorus and sulphur at 20, 40 DAS and after harvesting of black gram in acid Inceptisol of Meghalaya indicated that available phosphorus in soil increased with each successive increasing level of P application, however it showed decreasing trend with time intervals of 40 DAS and after harvesting of black gram at each successive dose of 40, 60 and 80 mg P kg-1 soil over 20 mg P kg-1 soil in the presence of S fertilization. Similarly, available sulphur in soil also increased with each successive increasing level of S application, whereas it also showed decreasing trend with time intervals of 40 DAS and after harvesting of black gram at each successive dose of 20, 30 and 40 mg S kg-1 soil over control as 10 mg S kg-1 soil in the presence of P fertilization.

Predicting Post-Harvest Soil Test Values in Hybrid Rice (Oryza Sativa L.) – Wheat (Triticum Aesitvum L.) Cropping Sequence Using a Multivariate Analysis Technique

ABSTRACTKnowledge of the initial soil fertility status is very crucial to make the soil test-based fertilizer recommendations and therefore it is necessary to develop alternative techniques to predict the post-harvest soil test values than analyzing the soils after every crop. The study was done to develop multiple linear regression (MLR) models to predict soil available nitrogen, phosphorus and sulfur in the hybrid rice-wheat cropping sequence. The post-harvest soil test values were considered as the dependent variable and initial soil nutrients applied nutrient through fertilizer and farmyard manure and grain yield as independent variables. In general, the accuracy of prediction for the calibration and validation models using the single year and two-year data model was significant and had a coefficient of determination was ≥0.75. Although the performance of MLR model to predict post-harvest soil N, P and S after the individual crop was better than that after whole rice-wheat cropping sequence, predictions of the post-rice-wheat sequence of soil N, P and S also had acceptable levels of accuracy. Thus, the concept of the using the MLR-based models to predict the post-harvest soil test values could be used in hybrid rice-wheat cropping sequence to make the soil test-based fertilizer recommendations to the individual crops or whole cropping sequence.

From Elemental Sulfur to Hydrogen Sulfide in Agricultural Soils and Plants.

Sulfur is an essential element in determining the productivity and quality of agricultural products. It is also an element associated with tolerance to biotic and abiotic stress in plants. In agricultural practice, sulfur has broad use in the form of sulfate fertilizers and, to a lesser extent, as sulfite biostimulants. When used in the form of bulk elemental sulfur, or micro- or nano-sulfur, applied both to the soil and to the canopy, the element undergoes a series of changes in its oxidation state, produced by various intermediaries that apparently act as biostimulants and promoters of stress tolerance. The final result is sulfate S+6, which is the source of sulfur that all soil organisms assimilate and that plants absorb by their root cells. The changes in the oxidation states of sulfur S0 to S+6 depend on the action of specific groups of edaphic bacteria. In plant cells, S+6 sulfate is reduced to S−2 and incorporated into biological molecules. S−2 is also absorbed by stomata from H2S, COS, and other atmospheric sources. S−2 is the precursor of inorganic polysulfides, organic polysulfanes, and H2S, the action of which has been described in cell signaling and biostimulation in plants. S−2 is also the basis of essential biological molecules in signaling, metabolism, and stress tolerance, such as reactive sulfur species (RSS), SAM, glutathione, and phytochelatins. The present review describes the dynamics of sulfur in soil and plants, considering elemental sulfur as the starting point, and, as a final point, the sulfur accumulated as S−2 in biological structures. The factors that modify the behavior of the different components of the sulfur cycle in the soil–plant–atmosphere system, and how these influences the productivity, quality, and stress tolerance of crops, are described. The internal and external factors that influence the cellular production of S−2 and polysulfides vs. other S species are also described. The impact of elemental sulfur is compared with that of sulfates, in the context of proper soil management. The conclusion is that the use of elemental sulfur is recommended over that of sulfates, since it is beneficial for the soil microbiome, for productivity and nutritional quality of crops, and also allows the increased tolerance of plants to environmental stresses.

Distribution of Nutrients in Sundarbans Coastal Ecosystem- A Case study

The distribution of nutrients were studied in six soil management units identified viz., Chandipur, Biprodaspur, Pathankhali, Manmathanagar-I, Manmathanagar-II and Bhupendranagar of Gosaba block (part) of sundarbans ecosystem. Data indicated that the soils were strongly acidic (< 4.5) to neutral in reaction and associated with marginal to severe salinity (> 13.3 dS m-1). The organic carbon content ranged from 0.67 to 1.66% in surface and 0.15 to 3.44% in sub-soils. The available nitrogen content varied from 90 to 502 kg ha-1 and it changed significantly with depth. The available phosphorus varied from 0.5 to 24.7 kg ha-1. Available potassium and sulphur in soils are very high, ranging from 178 to 572 kg ha-1 and 25 to 706 mg kg-1 respectively. DTPA -Fe and Mn varied from 18.9 to 336 and 2.17 to 37.6 mg kg-1 in soils being higher in sub-surface horizons, and DTPA- Zn and Cu ranged 0.27 to 4.73 and 0.63 to 14.5 mg kg-1 respectively.

Status of Sulphur and Boron in Soils of North Gujarat Region of India

The soils of North Gujarat region's were assessed for its Sulphur and Boron status due to its visible deficiency in plants. Study was conducted in three districts viz., Sabarkantha, Mehsana and Patan from which 60, 110 and 52 villages were selected and soils samples were collected with geo-tagging. A total of 1332 surface soil samples (Sabarkantha 360, Mehsana 660 and Patan 312) were collected from these respective districts. Analysis of these soil samples showed a wide variation in soil pH (6.04-9.72) from slightly acidic to alkaline. Organic carbon (OC) content ranged from 1.0 to 7.1 g kg-1, about 90, 65 and 74% of soil samples were found to be under the low OC in Mehsana, Sabarkantha and Patan districts, respectively. Available S content ranged from 1.7 to 68.5 mg kg-1 with a mean value of 15.6, 14.7 and 14.9 mg kg-1 in Mehsana, Sabarkantha and Patan districts, respectively. S deficiency in soils of all three districts was 18.1, 25.5 and 16.9 per cent, which appeared in medium-fertility class level as per Nutrient Index Value (NIV). The high magnitude of S deficiency was noticed in soils of Idar taluka (43.9 %) followed by Khedbrahma taluka (40.9%) of Sabarkantha district, showing medium-fertility class. Further, these samples were also found deficient in hot water-soluble boron (HWS-B) and it ranged from 0.06 to 3.12 mg kg-1 with a mean value of 0.44, 0.45 and 0.44 mg kg-1 in districts of Mehsana, Sabarkantha and Patan, respectively. The NIV indicated B fertility level of low to high. Per cent deficiency of B recorded about 29.4, 17.9 and 19.2 per cent in all three districts. A large scale of B deficiency was noticed in Satlasna taluka (52.4 %) of Mehsana district, which showed low fertility class.

Combined effects of carbonaceous-immobilizing agents and subsequent sulphur application on maize phytoextraction efficiency in highly contaminated soil.

The establishment of phytoextraction crops on highly contaminated soils can be limited by metal toxicity. A recent proposal has suggested establishing support crops during the critical initial phase by metal immobilization through soil amendments followed by subsequent mobilization using elemental sulphur to enhance phytoextraction efficiency. This 'combined phytoremediation' approach is tested for the first time in a pot experiment with a highly contaminated soil. During a 14-week period, relatively metal-tolerant maize was grown in a greenhouse under immobilization (before sulphur (S) application) and mobilization (after S application) conditions with soil containing Cd, Pb and Zn contaminants. Apart from the control (C) sample, the soil was amended with activated carbon (AC), lignite (Lig) or vermicompost (VC) all in two different doses (dose 1~45g additivekg-1 soil and dose 2~90g additivekg-1 soil). Elemental S was added as a mobilization agent in these samples after 9weeks. Biomass production, nutrient and metal bioavailability in the soil were determined, along with their uptake by plants and the resulting remediation factors. Before S application, Cd and Zn mobility was reduced in all the AC, Lig and VC treatments, while Pb mobility was increased only in the Lig1 and VC1 treatments. Upon sulphur application, Fe, Mn, Cd, Pb and Zn mobility was not significantly affected in the C, AC and VC treatments, nor total Cd, Pb and Zn contents in maize shoots. Increased sulphate, Mn, Cd, Pb and Zn mobilities in soil together with related higher total S, Mn, Pb and Zn contents in shoots were observed in investigated treatments in the last sampling period. The highest biomass production and the lowest metal toxicity were seen in the VC treatments. These results were associated with effective metal immobilization and showed the trend of steady release of some nutrients. The highest remediation factors and total elemental content in maize shoots were recorded in the VC treatments. This increased phytoremediation efficiency by 400% for Cd and by 100% for Zn compared to the control. Considering the extreme metal load of the soil, it might be interesting to use highly metal-tolerant plants in future research. Future investigations could also explore the effect of carbonaceous additives on S oxidation, focusing on the specific microorganisms and redox reactions in the soil. In addition, the homogeneous distribution of the S rate in the soil should be considered, as well as longer observation times.

Soil nutrient adequacy for optimal cassava growth, implications on cyanogenic glucoside production: A case of konzo-affected Mtwara region, Tanzania.

Soils in areas affected by konzo (a cassava cyanide intoxication paralytic disorder) are predominantly infertile and probably unable to supply cultivated cassava with the nutrients it needs to achieve optimal growth. Soil nutrient supply in these areas could also be influencing cyanogenic glucoside production in cassava, however there is hardly any knowledge on this. An assessment of soil nutrient levels on crop fields in konzo-affected areas was therefore carried out to determine their adequacy for optimal cassava growth. Konzo-affected Mtwara region of Tanzania, was used as a case study. Whether soil nutrient supply influences cyanogenic glucoside production in cassava cultivated in konzo-affected areas and how it could be doing this, was additionally investigated. To investigate this, correlations between total hydrogen cyanide (HCN) levels (a measure of cyanogenic glucoside content) in cassava roots and various soil nutrient levels on crops fields were carried out. This was followed by an investigation of relationships between cases of cassava cyanide intoxication and soil nutrient levels on crop fields from which the consumed toxic cassava roots had been harvested. Cases of cassava cyanide intoxication were used as a proxy for high cyanogenic glucoside levels in cassava roots. Logistic regression analysis was used in the latter investigation. Other important non-nutrient soil chemical characteristics, like pH and soil organic carbon, were also included in all analysis performed. The results revealed that most soil nutrients known to have reducing effects on cassava cyanogenic glucosides, like potassium (mean = 0.09 cmol/kg, SD = 0.05 cmol/kg), magnesium (mean = 0.26 cmol/kg, SD = 0.14 cmol/kg) and zinc (mean = 1.34 mg/kg, SD = 0.26 mg/kg) were deficient on several crop fields. The results also showed that cyanogenic glucosides in cassava roots could be increased with the increased supply of sulphur in soils in bitter cassava varieties (rs = 0.593, p = 0.032), and with the increased supply of P in soils in all cassava varieties (rs = 0.486, p = 0.026). The risk of cassava cyanide intoxication occurring (and thus high cyanogenic glucoside levels in cassava) was found to be likely increased by cultivating cassava on soils with high pH (X2 = 8.124, p = 0.004) and high iron (X2 = 5.740, p = 0.017). The study managed to establish that cassava grows under conditions of severe nutrient stress and that soil nutrient supply influences cyanogenic glucoside production in cassava cultivated in konzo-affected areas of Mtwara region. Despite the multiple soil nutrient deficiencies on crop fields, low soil fertility was however not the only probable cause of increased cyanogenic glucosides in cassava, as high soil nutrient levels were also found to be potential contributors.

Sulfur application combined with water management enhances phytoextraction rate and decreases rice cadmium uptake in a Sedum plumbizincicola - Oryza sativa rotation

Soil cadmium (Cd) contamination threatens food safety and human health. Increasing Cd phytoextraction efficiency by hyperaccumulators and growing safe products during remediation remain challenges. A pot experiment was conducted to explore the effects of different rates of sulfur (S) associated with alternating drying and wetting on a Sedum plumbizincicola-Oryza sativa rotation in Cd-contaminated neutral and calcareous soils. The oxidation of added S under aerobic conditions significantly decreased soil solution pH and increased soluble sulfate (SO42−), Cd and iron (Fe) concentrations in both soils. During the rice growing season the soil solution redox (Eh) decreased to < −200 mV and the solution pH increased to neutral during the first few days of flooding. Soluble SO42− and Cd in the S treatments decreased significantly with increasing duration of flooding. Sulfur addition promoted shoot Cd concentrations of S. plumbizincicola by 1.7–5.5 times on calcareous soil and 1.7–2.3 times on neutral soil compared to the controls. Rice yields increased but Cd concentrations decreased at suitable S addition rates. Appropriate sulfur amendment combined with water management can be a feasible strategy to enhance the Cd remediation efficiency of the hyperaccumulator and reduce the accumulation of Cd in the rice grains in this rotation.

Spatiotemporal variability in soil sulfur storage is changed by exotic Spartina alterniflora in the Jiuduansha Wetland, China

With an aim to determine whether Spartina alterniflora actively changes the habitat environment, thus facilitating its successful competition over native species, a field experiment was carried out at the Jiuduansha Wetland National Nature Reserve. Sulfur concentrations in the soil sediments were compared among wetlands dominated by the exotic Spartina alterniflora, the co-occurring native species S. mariqueter and unvegetated mudflat. The results show that the soil sulfur concentrations in the Spartina alterniflora community showed significant spatiotemporal variability with the years since invasion. The S. alterniflora community contained the highest concentrations of sulfur in the soil sediment. Moreover, the sulfur concentrations were higher in the initial invasion area than at the edges of the invading area. The was little difference in soil sulfur concentrations between communities containing native species S. mariqueter and unvegetated mudflat. There were significant correlations between soil sulfur concentrations and carbon and nitrogen concentrations; the soil nitrogen concentrations were negatively correlated with the sulfur concentrations, and the carbon concentrations were positively correlated with the sulfur concentrations. In different seasons, the concentration of sulfur is relatively higher in spring than which in other seasons. Furthermore, the sulfur concentrations at different soil depths also exhibited significant changes with depths. In addition, the soil sulfur concentrations associated with S. alterniflora also showed a trend of increasing first and then decreasing with depth, the soil sulfur concentrations in S. alterniflora soils were obviously higher than those in the S. mariqueter community and unvegetated mudflat, the maximum concentrations in S. alterniflora soils occurred at the depth of 40–60 cm. The findings of this study indicate that S. alterniflora increases wetland sulfur storage, which may explain the mechanism of expansion of S. alterniflora in the Jiuduansha Wetland.

Impacts of Anthropological Activities on Soils of Some Parts of Rivers State, Nigeria

The study is a post project implementation Environmental Monitoring (EM) of impacts of anthropological activities on levels of soil physicochemical parameters. The study evaluates levels of physicochemical parameters in soils of 9 locations in Port Harcourt and its environs in Rivers State, Nigeria, grouped into 3 categories; urbanized, industrialized and agricultural. Composite soil samples were collected between April to October 2018. Concentration levels of Benzene, Toluene, Ethyl-benzene, and Xylene (BTEX), Total Petroleum Hydrocarbon (TPH), Percent Total Organic Carbon (% TOC), Lead (Pb), Iron (Fe), Copper (Cu), Cadmium (Cd), Zinc (Zn), Calcium (Ca), Nickel (Ni), Sodium (Na), Potassium (K), Chromium (Cr), Magnesium (Mg), Manganese (Mn), and Sulphur (S) in soil was measured using standard analytical procedures. The study evaluates the impact magnitude (IM) of the obtained test values against control values. In industrial area, BTEX recorded the highest Impact Magnitude (IM) of 100% while TOC and TPH recorded 100.00% and 88.89% respectfully, and were classified as severely impacted (S). In the agricultural areas, TOC and Ni recorded IM of 88.89% while BTEX had an IM of 77.78% which were highest and were classified as severe impact (S). In urbanized areas, Ni and (Phosphate) PO43- recorded the highest IM of 88.89% and were classified as severe (S). The study establishes that urbanization, industrialization and agricultural activities do affect the level of physicochemical parameters in the study areas. Activities in industrial areas negatively impact on levels of BTEX, % TOC and TPH in soils. Activities in agricultural areas negatively impacted on levels of BTEX, NO3-, NO2- and SO42- in soils, and activities in urban areas negatively impact on levels of Ni, PO43-, Zn, Mn, TPH, % TOC and Ca in soils of the study areas. These findings form a reliable baseline data for future researchers in EM in the study areas. The study recommends EM of soil physicochemical parameters in the study area in order to ensure a healthy soil for food production in order for realization of Sustainable Development Goals (SDGs); Good Health and well-being, and sustainable cities and communities.

Consumption and alteration of different organic matter sources during remediation of a sandy sulfuric soil

Saturated acid sulfate soils with hypersulfidic material are productive wetland soils, but when they dry, they generate large amounts of sulfuric acid due to oxidation of pyrite to form sulfuric material (pH <4) and consequently sulfuric soils. After re-saturation of sulfuric soils and thus the re-establishment of reduced conditions, activity of sulfate reducing bacteria (SRB) can lead to a renewed formation of Fe sulfides and pH increase. Many SRB are heterotrophic and require sufficient available organic matter; however, little is known about OC consumption and changes of the composition of organic substrates during the amelioration process. To investigate remediation of a sandy, OC-poor sulfuric soil (initial pH = 2.5), short-term anoxic incubation experiments over a period of approx. 10 weeks were conducted after re-submerging under controlled laboratory conditions. We tested different organic matter quantities between 10% up to 200% of the native soil OC content. Besides wheat straw, we used lactate additions to test if this selectively promotes the activity of SRB, and thus, accelerates sulfate reduction and pH neutralization. The results showed that OC additions of ≥50% of native soil OC content and pre-adjustment of pH to values ≥5.0 were necessary to subsequently enable microbial reduction reactions to occur, which increased the pH to values ≥5.5. OC additions of ≥100% instead of 50% of native soil OC as wheat straw led to quicker changes of redox and pH values, to slightly higher microbial activity as indicated by CO2 release, and to higher proportions of newly-formed mineral-associated OC. The addition of OC as lactate solution to promote specifically SRB was only successful in combination with wheat straw addition. Here, the presence of lactate led to the quickest changes of pH and redox values and resulted in pH ≥7 and redox values ≤ −300 mV due to an active microbial population. Our results indicate that a diverse microbial community is more important for successful remediation than a selective promotion of SRB.