The influence of soil properties on 134Cs availability to sunflower and soybean plants

134Cs uptake by sunflower and soybean plants grown on seven different soils and its relation to soil properties were studied in a greenhouse pot experiment. Sunflower and soy bean plants were grown for three and two successive periods, respectively. 134Cs plant uptake was expressed as the transfer factor (TF) (Bq Kg-1 plant/Bq Kg-1 snl) and as daily plant uptake (flux) (Bq pot-1 day-) for the studied soils and for both plants, no consistent trend of TF5 with time was observed. The use of fluxes, in general, provided less variable results than TF5 and stronger functional relationships. A negative power functional relationship between exchangeable potassium expressed as a percentage of CEC of each soil and 134Cs TF5 and fluxes was found. This relationship explained up to 90% and 85% of the variability of 134Cs fluxes for sunflower and soybean plants, respectively. In addition, strong negative relationships between the potassium Q/I characteristics in soils and 134Cs uptake were observed and explained up to 93% and 76% of the variability of 134Cs uptake values for sunflower and soybean respectively. The results of the present study suggested that soil and plant characteristics may affect 134Cs uptake more than that of K. Finally, no 134Cs was detected in the oils extracted from seeds of both plants with high concentration of 134Cs.Σε πείραμα θερμοκηπίου με γλάστρες σε έξι επαναλήψεις μελετήθηκε η επίδραση των ιδιοτήτων επτά γεωργικών εδαφών στην απορρόφηση του 134Cs από φυτά ηλίανθου και σόγιας. Για να εκτιμηθεί η επίδραση του χρόνου στη διαθεσιμότητα του 134Cs τα φυτά του ηλίανθου καλλιεργήθηκαν για τρεις περιόδους και της σόγιας για δύο. Για την αξιολόγηση των αποτελεσμάτων χρησιμοποιήθηκαν δύο τρόποι, ο συντελεστής μεταφοράς του 134Cs (Σ Μ) (Bq kg-1 Ξ Β φυτού/Bq kg-1 Ξ Β έδαφος) και η ημερήσια απορρόφηση ανά γλάστρα (Η.Α.Γ.) (Bq γλάστρα-1 ημέρα-). Δεν παρατηρήθηκε κάποια σταθερή τάση (αυξητική ή πτωτική) των Σ Μ του 134Cs με το χρόνο. Βρέθηκε μία σημαντική αρνητική εκθετική σχέση των Σ Μ του 134Cs με τη συγκέντρωση του ανταλλάξιμου Κ όταν αυτό εκφράστηκε σαν ποσοστό της Ι.Α.Κ. των εδαφών, η οποία στη περίπτωση του ηλίανθου ερμήνευσε το 89% της διακύμανσης των Σ Μ του 134Cs. Με τη χρήση παραμέτρων των καμπυλών ρυθμιστικής ικανότητας των εδαφών για το Κ ερμηνεύθηκε έως και το 93% της διακύμανσης των τιμών της Η.Α.Γ. Παρατηρήθηκε διαφορετική κατανομή των 134Cs και Κ στα διάφορα μέρη των δύο φυτικών ειδών, ενώ είναι πιθανόν τα φυτά να απορροφούν επιλεκτικά το Κ σε βάρος του 134Cs από το έδαφος. Τέλος, δεν ανιχνεύθηκε 134Cs στα σπορέλαια που εκχυλίστηκαν από σπόρους των δύο φυτικών ειδών με μεγάλη συγκέντρωση 134Cs

Selenium Uptake by Lettuce Plants and Se Distribution in Soil Chemical Phases Affected by the Application Rate and the Presence of a Seaweed Extract-Based Biostimulant

To tackle selenium (Se) malnutrition, biofortification is among the proposed strategies. A biostimulant application in soils is thought to support a plant’s growth and productivity. Biofortification with Se(VI) may lead to a leaching hazard due to the high mobility of Se(VI) in the soil environment. In this study, the effect of the application of two Se(VI) rates—5 and 10 mg kg−1 soil—and a biostimulant on the Se uptake by lettuce plants and on the Se(VI) distribution in soil fractions following the plants harvest, was investigated. Phosphorus (P) and sulfur (S) concentrations in plants were also determined. A high Se(VI) rate suppressed plant growth, leading to a significant fresh weight decrease from 12.28 to 7.55 g and from 14.6 to 2.43 g for the control and high Se(VI) without and with biostimulants, respectively. Impaired plant growth was verified by the SPAD, NDVI and NDRE measurements. The significantly highest Se concentration in plants, 325 mg kg−1, was recorded for the high Se(VI) rate in the presence of the biostimulant. Compared to controls, the low Se(VI) rate significantly decreased P and increased the S concentrations in plants. The post-harvest soil fractionation revealed that, in the presence of the biostimulant, the Se(VI) soluble fraction increased from 0.992 to 1.3 mg kg−1 at a low Se(VI) rate, and decreased from 3.T85 to 3.13 mg kg−1 at a high Se(VI) rate. Nevertheless, at a low Se(VI) rate, 3.6 and 3.1 mg kg−1 of the added Se(VI) remained in the soil in less mobile forms, in the presence or absence of the biostimulant, respectively. This study indicated that the exogenous application of Se in soil exerted dual effects on lettuce growth and Se availability, depending on the level of selenate applied

Selenium Uptake by Lettuce Plants and Se Distribution in Soil Chemical Phases Affected by the Application Rate and the Presence of a Seaweed Extract-Based Biostimulant

To tackle selenium (Se) malnutrition, biofortification is among the proposed strategies. A biostimulant application in soils is thought to support a plant’s growth and productivity. Biofortification with Se(VI) may lead to a leaching hazard due to the high mobility of Se(VI) in the soil environment. In this study, the effect of the application of two Se(VI) rates—5 and 10 mg kg−1 soil—and a biostimulant on the Se uptake by lettuce plants and on the Se(VI) distribution in soil fractions following the plants harvest, was investigated. Phosphorus (P) and sulfur (S) concentrations in plants were also determined. A high Se(VI) rate suppressed plant growth, leading to a significant fresh weight decrease from 12.28 to 7.55 g and from 14.6 to 2.43 g for the control and high Se(VI) without and with biostimulants, respectively. Impaired plant growth was verified by the SPAD, NDVI and NDRE measurements. The significantly highest Se concentration in plants, 325 mg kg−1, was recorded for the high Se(VI) rate in the presence of the biostimulant. Compared to controls, the low Se(VI) rate significantly decreased P and increased the S concentrations in plants. The post-harvest soil fractionation revealed that, in the presence of the biostimulant, the Se(VI) soluble fraction increased from 0.992 to 1.3 mg kg−1 at a low Se(VI) rate, and decreased from 3.T85 to 3.13 mg kg−1 at a high Se(VI) rate. Nevertheless, at a low Se(VI) rate, 3.6 and 3.1 mg kg−1 of the added Se(VI) remained in the soil in less mobile forms, in the presence or absence of the biostimulant, respectively. This study indicated that the exogenous application of Se in soil exerted dual effects on lettuce growth and Se availability, depending on the level of selenate applied

Efficient urea-N and KNO

Vegetable production demands high nitrogen inputs. Fertigation is a means to increase fertilizer-N use by plants. However, the effect of different N sources and doses, and how they relate to the total available N in soils are poorly known. In this study we applied 15N-labeled fertilizers to green pepper in the field using a drip irrigation system during the dry summer. KNO3-N and urea-N were applied at a total of 6, 12 and 18 g plant−1. Our results show that urea was as effective as KNO3 as a N source. The fertilizer-N utilization efficiency was dramatically reduced at higher N doses, from 48% for the 6 g N plant−1 dose to 36% and 26% for the 12 and 18 g N plant−1 doses, respectively. However, the N in plants derived from fertilizer consistently exceeded 60%, indicating high availability of fertilizer-N even at the lowest dose. Negative added nitrogen interactions – the effect of added N on the fate of soil-N – were observed, particularly at high fertilizer-N doses. The fertilizer-N utilization efficiency calculated by the difference method was lower compared with the 15N enrichment method. This clearly indicates luxury N applications and excess N availability brought about by precise localized placement of fertilizer-N that leads to limited uptake of the available soil-N. N leaching risks in the following rain period should therefore be based on both the residual fertilizer-N and the increased amounts of residual soil mineral-N

Efficacy of EDTA and Olive Mill Wastewater to Enhance As, Pb, and Zn Phytoextraction by Pteris vittata L. from a Soil Heavily Polluted by Mining Activities

A pot experiment was conducted to evaluate the effect of Na2-EDTA 0.01 M (E) and olive mill wastewater 15% (OMW) on As, Pb, and Zn uptake by Pteris vittata L. grown in a soil highly contaminated by mining activities. A two-factor experimental design was followed; 3 treatments (E, OMW, and E + OMW) × 2 batches (single or double dose). Six weeks after the P. vittata transplanting, all pots received the selected dose of each treatment (Batch I). At 8 weeks, in half of the pots, a second dose of the same treatments was added (Batch II). Plants were harvested after 10 weeks and As, Pb, and Zn concentrations were determined in fronds and roots. Depending on the element, both treatment and batch effects were significant. In Batch II, EDTA application resulted in a 55% increase of As and 9- and 4-fold of Pb and Zn concentrations in the fronds, while OMW treatment substantially reinforced plant uptake when combined with EDTA. Roots to fronds translocation of the metal(loid)s highly increased in Batch II. After harvest, composite soil samples of all treatment–batch combinations were subjected to sequential extraction, but no significant differentiations of As, Pb, and Zn partitioning in soil phases were detected

Growing of the Cretan Therapeutic Herb <i>Origanum Dictamnus</i> in The Urban Fabric: The Effect of Substrate and Cultivation Site on Plant Growth and Potential Toxic Element Accumulation

Origanum dictamnus L. (Lamiaceae) is a perennial herb endemic to the Greek island of Crete, widely used for tea preparation, medicinal purposes, and food flavoring, as well as an ornamental plant. The aim of this work was to introduce the species to the green roof sector while serving urban agriculture. Thus, its growth potential was investigated, along with the content of nutrients (N, P, K, Na) and the accumulation of heavy metals (Cu, Pb, Ni, Mn, Zn, Fe) in its tissues, in two cultivation sites in Athens, Greece, i.e., an extensive green roof and at ground level next to a moderate traffic road. Cultivation took place in plastic containers with a green roof infrastructure fitted, in two substrate types (grape marc compost, perlite, and pumice 3:3:4 v/v, and grape marc compost, perlite, pumice, and soil 3:3:2:2 v/v), with 10 cm depth. Plant growth was favored by the soil substrate, but it was also satisfactory in the soilless one. Cultivation site affected heavy metal accumulation, resulting in higher concentrations both in leaves and in flowers at street level, while no differences were observed in roots. Washing the tissues reduced heavy metal concentrations only in leaves produced at the street level. Substrate type significantly affected Mn concentration in all plant tissues and Fe in roots, with the highest values measured in the soil substrate. Thus, O. dictamnus could be effectively cultivated in sustainable green roofs, better on a soilless substrate to lower construction weight. Careful selection of the cultivation site could minimize contamination with environmental pollutants if human consumption is also desired

Assessment of Potentially Toxic Element Contamination in the Philippi Peatland, Eastern Macedonia, Greece

The Philippi peatland is considered the biggest peat deposit in the Balkan Peninsula and one of the deepest in the world. The purpose of this study was to access the impact of eight potentially toxic elements (PTEs), i.e., As, Se, Pb, Cr, Ni, Zn, Mn and Cu, on the local environment. PTE content was determined in corn grains and surface soil samples collected from 16 sites in the peatland, and pollution indices were calculated to evaluate the environmental risks. Soil organic matter ranged between 93 and 557 g kg−1 soil, whereas the soil pH was >7, classifying the soils as neutral to slightly alkaline. Mean PTE contents in soil samples were 24.6 mg kg−1 soil for As, 1.68 mg kg−1 soil for Se, 113 mg kg−1 soil for Pb, 32 mg kg−1 soil for Cr, 36.3 mg kg−1 soil for Ni, 141.4 mg kg−1 soil for Zn, 35.5 mg kg−1 soil for Cu and 845 mg kg−1 soil for Mn. In corn grain samples, 0.06 mg kg−1 grain for As, 0.14 mg kg−1 grain for Se, 1.34 mg kg−1 grain for Cr, 0.69 mg kg−1 grain for Ni, 27 for Zn, 8.4 mg kg−1 grain for Cu and 3.2 mg kg−1 grain for Mn were recorded. No Pb was detected in the corn grains. The bioaccumulation factor (BF) was high for Cu, Zn and Se, indicating increased mobility of these elements in the soils and preferential plant uptake. For most soil samples, the geoaccumulation index (Igeo) and single pollution index (PI) showed low to moderate contamination. However, Igeo and PI values of Se in many sampling sites and of Pb and Zn in few were substantially increased, pointing to heavily contaminated soils. According to potential ecological risk (RI), the PTE content in the peat soils of Philippi imposes low to moderate risk on the environment

Using the Halophyte Crithmum maritimum in Green Roofs for Sustainable Urban Horticulture: Effect of Substrate and Nutrient Content Analysis including Potentially Toxic Elements

The effect of substrate type and cultivation site in the urban fabric on growth, nutrient content and potentially toxic element (PTE) accumulation in tissues of the halophyte Crithmum maritimum was studied. Plantlets were cultivated for twelve months in containers with a green-roof infrastructure fitted and placed either on an urban second-floor roof or on ground level by the side of a moderate-traffic street. Two substrate types were used; one comprising grape marc compost, perlite and pumice (3:3:4, v/v) and one composed of grape marc compost, perlite, pumice and soil (3:3:2:2, v/v), with 10 cm depth. Plants grew well on both sites, although aboveground growth parameters and nutrient content in leaves were greater at street level. Both cultivation site and substrate type affected heavy-metal accumulation in plant tissues. Cu, Ni and Fe concentrations in leaves and Pb in roots were higher in street-level-grown plants compared to the roof-grown plants, and concentrations of Cu and Mn in leaves and Fe in both leaves and roots were lower in the soilless substrate compared to the soil-substrate, making the soilless type preferable in the interest of both safer produce for human consumption and lower construction weight in the case of green-roof cultivation

Enhanced As, Pb and Zn Uptake by Helianthus annuus from a Heavily Contaminated Mining Soil Amended with EDTA and Olive Mill Wastewater Due to Increased Element Mobilization, as Verified by Sequential Extraction Schemes

Soils close to former mines or metallurgical facilities often contain extreme concentrations of potentially toxic elements (PTEs), and among soil remediation actions needed, enhanced phytoextraction techniques using chelating agents could be a very promising option. In this context, a pot experiment was conducted to evaluate the effect of Na2-EDTA, olive mill wastewater (OMW), and their combination (EDTA + OMW) on As, Pb and Zn uptake by Helianthus annuus (sunflower), grown in a heavily contaminated soil from Lavrio, Greece. After harvest, aboveground and belowground biomass and the concentrations of As, Pb and Zn were determined. Additionally, composite soil samples of all treatments were subjected to appropriate sequential extraction procedures for each PTE. Results showed that although nonstatistically significant effects on plant growth and As concentration were observed, Pb and Zn plant concentrations increased by the EDTA addition, alone or combined with OMW. When the total bioavailability parameter was assessed, EDTA treatment was also found to significantly enhance As uptake (50% increase, p &le; 0.05). These results were further supported by the respective sequential extraction schemes in which both Pb and As showed increased concentration in the corresponding more soluble soil fractions, probably as an outcome of partial Fe&ndash;Mn amorphous oxide dissolution. Our study thus suggests that the applied treatments of EDTA, OMW or their combined application could play a key role as reductive agents in enhancing the mobility of these PTEs in the soil environment, triggering their increased uptake by H. annuus