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The creation of high quality plants and their maintenance depends, primarily, on proper fertilization, deriving mainly from the knowledge of their nutrient requirements (NR). Spray-applied chlormequat chloride (CCC), at the concentrations of 3000 and 6000 mg L-1, has been reported to contribute to the production of attractively flowering Lantana camara L. subsp. camara (lantana) plants. However, no information is available about the NR of these plants. The effects of the aforementioned CCC concentrations plus 0 mg L-1 (control) on specific leaf area (SLA) and leaf potassium (K), phosphorus (P), calcium (Ca), iron (Fe) and manganese (Mn) contents of lantanas were examined under the 0% and 66% shading levels. Chlormequat chloride (3000 and 6000 mg L-1) decreased, generally, SLA of lantanas compared to control, at both shadings. Increased SLA values were estimated with increased shading. Phosphorus content increased with the increased CCC concentrations at 66% shading level. Phosphorus and Fe contents increased while Ca and Mn decreased with the increasing shading. The results of our study may contribute to the planning of a fertilization program for CCC-treated Lantana plants, a promising genus in landscaping in many countries around the world. [ABSTRACT FROM AUTHOR]

The internal structure, iron and manganese distributions of Fe-Mn nodules from imperfectly drained soils of central Greece were studied by scanning electron microscopy (SEM) and elemental analysis. Nodules exhibited a differentiated structure with discontinuous concentric rings as expression of their redox history. Fe and Mn have shown distinct repartition and were distributed mainly in concentric bands. The microstructure and the arrangement of iron-manganese compounds reflect the periodical development and the relative slow accretion rates of the studied nodules. These properties provide ample opportunity for adsorption and isolation of heavy metals from the soil system. [ABSTRACT FROM AUTHOR]

The article offers information on increase in yields of wheat crop by incorporation of elemental sulfur as fertilizer coating material. Topics discussed include information on fertilizers which contains elemental sulfur; information on the rhizospheric soil in which sulfur was used contains low concentration of humic substances and sands; and information on decreased crop yield in soil with phosphate content coupled with low potassium content.

The article offers information on the impact of elemental sulfur coated fertilizers application over calcareous soil under wheat cultivation. It mentions that the elemental sulfur coating of the applied fertilizers significantly boosted the action of the above mentioned plant growth promoting rhizobacteria, which in turn contributed to the mobilization of immobilized sulfate. It presents information on fertility dynamics and microbial population dynamics in crop's rhizosphere.

In the present study, the ability of a modified CaCl 2 zeolite (Ca-Z) to both increase Se(IV) availability and restrict Se(VI) mobility in soils is examined. As it was resulted from batch experiments and verified by X-ray absorption fine structure (XAFS) and X-ray fluorescence (XRF) spectroscopies, higher amounts of both Se species adsorbed on Ca-Z compared to natural zeolite (Z-N) forming outer-sphere complexes while the oxidation state did not alter during agitation of samples. Thereafter, Ca-Z was incorporated in six Greek soils, divided into acid and alkaline, at a 20% (w/w) rate and a series of equilibrium batch experiments were performed with soils alone and soils-Ca-Z mixtures to investigate sorption and desorption processes and mechanisms. The acid soils, either treated with Ca-Z or not, adsorbed higher amounts of Se(IV) than alkaline ones, whereas soils alone did not adsorb Se(VI) but impressively high adsorption of Se(VI) occurred in the Ca-Z-treated soils. Desorption of Se(IV) was higher from the Ca-Z-treated soils and especially from the acid soils. Higher distribution coefficients of desorption than the distribution coefficients of sorption were observed, clearly pointing to a hysteresis mechanism. The experimental data fitted with Langmuir and Freundlich isotherms. In the presence of Ca-Z, the Langmuir q m values increased indicating higher Se(IV) retention while Langmuir b L values decreased suggesting lower bonding strength and higher Se(IV) mobility. Overall, treating the soils with Ca-Z increased Se(IV) adsorption and mobility whereas it provided sites for Se(VI) adsorption that did not exist in the studied soils., (© 2023. The Author(s).)

The established practices of intensive agriculture, combined with inadequate soil Κ replenishment by conventional inorganic fertilization, results in a negative environmental impact through the gradual exhaustion of different forms of K reserves in soils. Although biochar application as soil amendment has been established as an approach of integrated nutrient management, few works have focused on the impact of biochar application to soil K availability and crop uptake. This review provides an up-to-date analysis of the published literature, focusing on the impact of biochar in the availability of potassium in soil and crop growth. First, the effect of biomass type and pyrolysis temperature on potassium content of biochar was assessed. Second, the influence of biochar addition to the availability of potassium in soil and on potassium soil dynamics was examined. Finally, alternative methods for estimating available K in soils were proposed. The most promising biomasses in terms of potassium content were grape pomace, coffee husk and hazelnut husk however, these have not been widely utilized for biochar production. Higher pyrolysis temperatures (>500 °C) increase the total potassium content whereas lower temperatures increase the water-soluble and exchangeable potassium fractions. It was also determined that biochar has considerable potential for enhancing K availability through several distinct mechanisms which eventually lead directly or indirectly to increased K uptake by plants. Indirect mechanisms mainly include increased K retention capacity based on biochar properties such as high cation exchange capacity, porosity, and specific surface area, while the direct supply of K can be provided by K-rich biochar sources through purpose-made biochar production techniques. Research based on biochar applications for soil K fertility purposes is still at an early stage, therefore future work should focus on elucidating the mechanisms that define K retention and release processes through the complicated soil-biochar-plant system., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Soil contamination with potentially toxic elements (PTEs) is considered one of the most severe environmental threats, while among remediation strategies, research on the application of soil amendments has received important consideration. This review highlights the effects of biochar application on soil properties and the bioavailability of potentially toxic elements describing research areas of intense current and emerging activity. Using a visual scientometric analysis, our study shows that between 2019 and 2020, research sub-fields like earthworm activities and responses, greenhouse gass emissions, and low molecular weight organic acids have gained most of the attention when biochar was investigated for soil remediation purposes. Moreover, biomasses like rice straw, sewage sludge, and sawdust were found to be the most commonly used feedstocks for biochar production. The effect of biochar on soil chemistry and different mechanisms responsible for PTEs' immobilization with biochar, are also briefly reported. Special attention is also given to specific PTEs most commonly found at contaminated soils, including Cu, Zn, Ni, Cr, Pb, Cd, and As, and therefore are more extensively revised in this paper. This review also addresses some of the issues in developing innovative methodologies for engineered biochars, introduced alongside some suggestions which intend to form a more focused soil remediation strategy.

Selenium deficiency in humans and animals can be reduced through dietary supplementation. Therefore, Se biofortification strategy is important in food plants and pastures. In this study, the effects of selenium (Se) addition (4 mg Se/kg) as sodium selenate (Na 2 SeO 4 ) on lettuce ( Lactuca Sativa L.) and berseem cultivation ( Trifolium alexandrinum L.) were investigated. The experiment was conducted under greenhouse conditions with two different soil types, an acidic (pH = 6.3) and an alkaline (pH = 8.0) soil with different organic matter content, in a completely randomized design. The results indicated higher Se content in berseem cultivated on acidic soil. It was also observed a significant reduction (~ 45%) in plant biomass of lettuce in the acidic soil combined with Se application. The results showed that leaf Se content was negatively correlated with soil organic matter. The decreased Se content in plants cultivated on the alkaline soil with high organic matter content support that the effect of pH on Se uptake decreased as the soil organic matter content increased., Competing Interests: The authors declare no conflict of interest.

Application of chelating and reductive agents in soils can increase the availability of potentially toxic elements facilitating their uptake by plants. This study discusses the effect of single or combined EDTA (E), sodium dithionite (SD), and olive mill wastewater (OMW) treatments on As, Pb, and Zn mobility over time in a heavily contaminated mine-affected soil. Soil samples were incubated for 1, 3, 7, 15, 30, 60, and 90 days and at each incubation time the easily mobilizable fraction obtained by (NH 4 ) 2 SO 4 (for As) and CH 3 COOH (for Pb/Zn). The results showed that the highest availability of As (mean value 41 mg kg -1 ) was observed for the EDTA treatment followed by E+OMW (mean value 32 mg kg -1 ) and E+SD+OMW (mean value 27 mg kg -1 ). For Pb and Zn, significantly higher available concentrations were obtained by the EDTA and E+OMW treatments (mean values 2532 mg kg -1 and 1427 mg kg -1 for Pb and Zn respectively) followed by the E+SD (mean value 2259 and 1333 mg kg -1 for Pb and Zn) and E+SD+OMW treatments (mean value 2388 and 1340 mg kg -1 for Pb and Zn). Moreover, the incubated for 90 days soil samples subjected to two different sequential extraction protocols (SEPs): Wenzel (for As) and BCR (for Pb, Zn, Fe, and Mn). The results showed that As, Pb, and Zn mobility was mainly regulated by the amorphous Fe oxides. Our findings suggest that OMW application in soils should focus more attention since when combined with other amendments produced contradictory results.

The demand to develop fertilizers with higher sulfur use efficiency has intensified over the last decade, since sulfur deficiency in crops has become more widespread. The aim of this study was to investigate whether fertilizers enriched with 2% elemental sulfur (ES) via a binding material of organic nature improve yield when compared to the corresponding conventional ones. Under the scanning electron microscope, the granules of the ES-containing fertilizer were found to be covered by a layer of crystal-like particles, the width of which was found to be up to 60 μm. Such a layer could not be found on the corresponding conventional fertilizer granules. Several fertilization schemes with or without incorporated ES were tested in various durum wheat varieties, cultivated in commercial fields. The P-Olsen content of each commercial field was found to be correlated with the corresponding relative change in the yields (YF/YFBES) with a strong positive relationship. The content of 8 ppm of available soil phosphorus was a turning point. At higher values the incorporation of ES in the fertilization scheme resulted in higher yield, while at lower values it resulted in lower yield, compared with the conventional one. The experimental field trials that established following a randomized block design, were separated in two groups: One with P-Olsen ranging between 18⁻22 ppm and the other between 12⁻15 ppm, the results of which corroborated the aforementioned finding. The use of ES in all portions of fertilization schemes provided higher relative yields. The coexistence of ES with sulfate in the granule was more efficient in terms of yield, when compared to the granule enriched with ES alone under the same fertilization scheme and agronomic practice. The application of fertilizer mixtures containing the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), ES and ammonium sulfate resulted in even higher relative yields. Yield followed a positive linear relationship with the number of heads per square meter. In this correlation, the P-Olsen content separated the results of the two groups of blocks, where the applied linear trend line in each group presented the same slope.

Toxic chromium [(Cr(VI)] in food chain has created an alarming situation for human life and ecosystems. The present study through a greenhouse pot experiment aims to (a) investigate the ability of organic matter in reducing Cr uptake by lettuce (Lactuca sativa L.) from a sandy loam soil irrigating with Cr(VI)-water, (b) to provide a way for the restriction of Cr transfer from contaminated soils and irrigation water to plants/crops and (c) to contribute to the better management of soil (land) and water use, without reduction of the agricultural production. Since soil and groundwater contamination by Cr is a potential risk in a worldwide scale, due to industrial activities and/or natural processes, organic carbon may play a key role in the mobility of added Cr(VI) to soil via irrigation water, in a significant way. The cultivation of lettuce, using organic matter in the form of leonardite (10 and 30 wt%) and Cr(VI)-irrigation water (100, 200 and 300 mgL -1 ), showed that the uptake of Cr in both shoots and roots increased with increasing concentration of Cr in the irrigation water. The highest Cr values in shoots (average = 10 mg/kg) and in roots (average = 28 mg/kg) were recorded in those plants cultivated in soil after the addition of Cr(VI)- water without organic matter, whereas the lowest Cr values in shoots (average = 0.44 mg/kg) and in roots (average = 0.7 mg/kg) were recorded in those plants cultivated in soil with addition of 30 wt% organic matter. The used leonardite as organic matter that is an oxidized form of lignite, due to its high content of humic acid is considered to be a useful organic fertilizer that provides possibilities for combining food production with soil protection. Therefore, the application of the natural organic material leonardite, as a land management technique, seems to be a cost-effective method consistent to related protocols for the protection of the soil quality., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Emissions from civil airports are similar to those observed in industrial and urban areas. While air pollution and noise levels are regularly monitored and assessed, information on the status of heavy metals in soils close to airport facilities is limited. In this study, we monitored and assessed heavy metal distribution in soils close to Athens International Airport (AIA) in Attica, Greece. Following a grid sampling scenario, topsoil samples were collected from 86 sites at the periphery of AIA and total and available forms of Cu, Zn, Fe, Mn, Ni, Cr, Pb, and Ba concentrations were determined in aqua regia and DTPA soil extracts, respectively. Median concentration values for both metal forms are not considered as particularly high. However, 90th percentile concentration values for some metals are high, indicating soil enrichment. Evaluation of enrichment factor (EF) and availability ratio (AR) values and EFs spatial distribution have led to consistent conclusions of secondary and ongoing metal accumulation in the soils of the studied area. Tessier sequential extraction procedure was applied to 10% of the soil samples and the results showed high potential availability of Pb, Mn, Cu, and Ni, further supporting the continuous metal accumulation in the studied soils.

The Thriassio plain is located 25 km west of Athens city, the capital of Greece. Two major towns (Elefsina and Aspropyrgos), heavy industry plants, medium to large-scale manufacturing, logistics plants, and agriculture comprise the main land uses of the studied area. The aim of the present study was to measure the total and available concentrations of Cr, Zn, Ni, Pb, Co, Mn, Ba, Cu, and Fe in the top soils of the plain, and to asses soil contamination by these metals by using the geoaccumulation index (I geo), the enrichment factor (EF), and the availability ratio (AR) as soil pollution indexes. Soil samples were collected from 90 sampling sites, and aqua regia and DTPA extractions were carried out to determine total and available metal forms, respectively. Median total Cr, Zn, Ni, Pb, Co, Mn, Ba, Cu, and Fe concentrations were 78, 155, 81, 112, 24, 321, 834, 38, and 16 × 10(3) mg kg(-1), respectively. The available fractions showed much lower values with medians of 0.4, 5.6, 1.7, 6.9, 0.8, 5.7, 19.8, 2.1, and 2.9 mg kg(-1). Though median total metal concentrations are not considered as particularly high, the I geo and the EF values indicate moderate to heavy soil enrichment. For certain metals such as Cr, Ni, Cu, and Ba, the different distribution patterns between the EFs and the ARs suggest different origin of the total and the available metal forms. The evaluation of the EF and AR data sets for the soils of the two towns further supports the argument that the EFs can well demonstrate the long-term history of soil pollution and that the ARs can adequately portray the recent history of soil pollution.