Soil Zn Concentrations Research Articles

Comprehensive assessment of heavy metals in soil-crop system based on PMF and evolutionary game theory

The traditional assessment of farmland environmental quality usually focuses on soil heavy metals, but ignores agricultural produce safety. It is urgent to comprehensively assess the effects of farmland environmental quality based on soil quality and produce safety. To fill this gap, the comprehensive assessment method was improved based on previous studies, which was used to assess the pollution level of heavy metals in soil-crop system of Shenyang, Liaoning Province, Northeast China. In addition, this study also made a comprehensive analysis of pollution sources based on positive matrix factorization (PMF) model, and discussed soil-crop system income stability by evolutionary game theory. The mean concentrations of As, Cd, Cr, Hg, Pb, Cu, Zn, and Ni in soil exceeded the corresponding Shenyang soil background values (5.68 %, 14.36 %, 57.61 %, 7.86 %, 30.32 %, 5.21 %, 211.72 %, 171.88 %). The results showed that about 28.28 % of paired soil-crop points were polluted by heavy metals, especially rice-soil points. Furthermore, heavy metals in crops may be transmitted less from soil and more from other environmental media. The PMF analysis results showed that there were six pollution sources in study area, and the major contributor of pollution were agricultural activities, traffic-related activities, and industrial activities. In farmland environment protection, the only stable strategy is soil-crop system, and soil-crop system is better than the benefits of single soil or crop from the perspective of benefits. This study provides a scientific and reliable method to combine soil quality with produce safety to assess the risk of heavy metals in farmland.

Monitoring the concentrations of Cd, Cu, Pb, Ni, Cr, Zn, Mn and Fe in cultivated Haplic Luvisol soils using near-infrared reflectance spectroscopy and chemometrics

This study illustrates the successful application of near-infrared reflectance spectroscopy extended with chemometric modeling to profile Cd, Cu, Pb, Ni, Cr, Zn, Mn, and Fe in cultivated and fertilized Haplic Luvisol soils. The partial least-squares regression (PLSR) models were built to predict the elements present in the soil samples at very low contents. A total of 234 soil samples were investigated, and their reflectance spectra were recorded in the spectral range of 1100–2500 nm. The optimal spectral preprocessing was selected among 56 different scenarios considering the root mean squared error of prediction (RMSEP). The partial robust M-regression method (PRM) was used to handle the outlying samples. The most promising models were obtained for estimating the amount of Cu (using PRM) and Pb (using the classic PLS), leading to RMSEP expressed as a percentage of the response range, equal to 9.63% and 11.5%, respectively. The respective coefficients of determination for validation samples were equal to 0.86 and 0.58, respectively. Assuming similar variability of model residuals for the model and test set samples, coefficients of determination for validation samples were 0.94 and 0.89, respectively. Moreover, the favorable PLS models were also built for Zn, Mn, and Fe with coefficients of determinations equal to 0.87, 0.87, and 0.79.

Sustainability assessment of topsoil ecology in Chongqing, China based on the application of livestock and poultry manure

China is the world's largest livestock and poultry breeding country. Heavy metal trace element additives are widely used to prevent animal diseases and promote their growth. China produces approximately 3.8 billion tons of livestock and poultry manure annually, and untreated livestock and poultry manure causes a large amount of heavy metal elements to enter the soil environment. Currently, there is limited research on the accumulation of heavy metals in the soil due to the continuous application of livestock and poultry manure, the resulting pollution risk and the negative effects on soil ecology sustainability. This study thoroughly investigated the effects of livestock and poultry manure on the composition and function of soil microbial, and heavy metal resistance genes using 16S and metagene sequencing and 6 years of field experiments. The application of livestock and poultry manure for 6 consecutive years increased the accumulation of zinc (Zn), copper (Cu), mercury (Hg), and chromium (Cr) in the soil at the experimental sites, and cadmium (Cd) and Hg had higher potential risk levels (single potential ecological risk coefficients (Eri) of Hg and Cd were 190.49–336.52 and 385.43–468.52, respectively). Firmicutes and Zoopagomycota were significantly correlated with the soil Zn and Cd contents and pH. After continuous application of manure, the relative abundance of Hg resistance genes (merA) in soil increased by 7.3–8.2 times compared with inorganic feitilizer treatment (IF), and Cu resistance genes (copF and actP) increased by 2.45–5.45 times and 3.8–4.6 times. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt2) and metagenomic function prediction indicated that resistance genes, antioxidant response, and metal output played an important role in heavy metal bioresistance and biotransformation. This work presented heavy metal contents, microbial composition and resistance genes in continuous application of livestock and poultry manure in China, and these data will be of great use in the surveillance, maintenance, and biological removal of heavy metals in manure.

The Clean Water Act and biosolids: A 45‐year chronological review of biosolids land application research in Colorado

The 1972 U.S. Clean Water Act set forth the generation of biosolids. In Colorado, biosolids land application research began in 1976 and continues today. Pastureland research suggested that sewage effluent could effectively be land applied to benefit aboveground plant growth and to polish water prior to reaching receiving waters. Forest wildfire-affected ecosystems can also benefit from biosolids applications; application rates of up to 80 Mg ha-1 can lead to greater plant establishment, soil microbial activity, and nutrient turnover and reduced nutrient and heavy metal concentrations in runoff below livestock and USEPA drinking water standards. Long-term (24-yr) observations in oil shale-mined lands showed that biosolids (up to 224 Mg ha-1 ) can have a positive effect on microbial-mediated nutrient cycling and, in turn, on aboveground plant community structure. Biosolids applications of up to 40 Mg ha-1 in high-elevation shrubland ecosystems, dominated by Mo-containing shale deposits, can aid in reducing imbalances between Mo and Cu in soils and plants; excessive plant Mo, when consumed by ruminants, can lead to molybdenosis. Biosolids and lime applications (both at 224 Mg ha-1 ) have been shown to improve long-term reclamation success on acid-generating, heavy metal-containing fluvial mine tailings. Thirty years of grazing land research, focused on soil and aboveground plant benefits, illustrate that soil health and plant productivity can be improved to the greatest extent at biosolids application rates close to 10 Mg ha-1 . Finally, 40 yr of dryland agroecosystem research (a) have helped identify biosolids N fertilizer equivalency (∼8kg N Mg-1 ) and thus dryland winter wheat application rates (e.g., 4.5-6.7 dry Mg ha-1 ); (b) have identified first-year mineralization rates of 25-32%; (c) dispute the "time bomb" theory by showing that plant metal uptake follows an exponential rise to a maximum; (d) showcase economic return to producers via increased wheat grain protein content; (e) suggest that biosolids-borne proteins and their degradation products are labile C and N sources; (f) have led to long-term tracking of micronutrients and heavy metals in soils and revealed that plants-soil concentrations will not lead to groundwater degradation and that plants are safe for human consumption; and (g) have shown that biosolids provide Zn, helping to overcome soil deficiencies and enhancing Zn biofortification in wheat grain. This latter point is important because ∼2 billion people globally suffer from Zn deficiencies. Forty-five years of research in Colorado have proven that biosolids can enhance environmental quality, improve soil health, and produce healthy food products.

Coronilla juncea, a native candidate for phytostabilization of potentially toxic elements and restoration of Mediterranean soils

Soil contamination pattern due to industrial activities often leads to high concentrations of potentially toxic elements (PTE) decreasing with depth. This spatial heterogeneity of the soil contamination may have significant consequences on the soil properties and soil living communities. We evaluated the effects of both surface and solum soil contamination heterogeneity on Coronilla juncea L. (Fabaceae) functional traits in field conditions and the phytostabilization potential of this species. Plant and soil samples were collected on 3 sites along a PTE contamination gradient. The correlations between PTE concentration in plant and soil samples at 2 depths, physico-chemical properties of soil, plant biomass and soil microbial activity were tested. Field measurements highlight a decreasing PTE concentration with soil depth in addition to an important surface heterogeneity of As, Cu, Pb, Sb and Zn soil concentrations. Root PTE concentrations in C. juncea did not follow soil PTE concentrations. Concentrations of PTE in the root parts were higher than those of the aerial parts. Low PTE translocation and root symbioses with microorganisms suggest that this native plant species may play a role as engineer species with positive implications for the phytostabilization of Mediterranean PTE contaminated soils and their ecological restoration.

Effect of Land Use/Land Cover Change on the Concentration of Se and Heavy Metals in Soils from a "Return Cropland to Forest" Area, Southwest China

Human activities (land use) and environmental change (land cover change) affect the concentration of Se and heavy metals in soils. The implementation of the "Return Cropland to Forest (RCF)" ecological project has changed the land use and cover, which has provided an ideal experimental area for studying the effects of land use and cover change on selenium (Se) and heavy metals in the soil. In this study, 91 top soil samples from different land use and land cover types, including dry land, paddy land, natural forest land, and secondary forest land, were collected, and the contents of Se, heavy metals, and soil organic matter (SOM) and pH were analyzed. The results showed that:① the average values of ω(Se) (0.42×10-6), ω(As) (13.0×10-6), and ω(Sb) (1.03×10-6) were higher than the soil background values of western Chongqing. ② The concentrations of Se, Cd, Cr, Ni, Pb, and Zn in soils from secondary forest land were significantly higher than those from dry land soils, suggesting that the Se and heavy metals might have significantly increased in the surface soil after the implementation of the RCF ecological project. ③ The SOM was the key controlling factor for the enrichment and distribution of Se and heavy metals in the top soils. Our results indicated that the land use and land cover change would deeply impact the concentrations of Se and heavy metals in the top soils via influencing the soil properties, especially the SOM.

Contribution of arbuscular mycorrhizal fungi and soil amendments to remediation of a heavy metal-contaminated soil using sweet sorghum

Owing to their potential advantages such as waste reduction, recycling, and economic attributes, fast-growing bioenergy crops have the capacity to effectively phytoremediate heavy metal-contaminated soils. However, little is known about the role of microbial and chemical amendments in phytoremediation using bioenergy crops. Here, we studied the contributions of inoculation with the arbuscular mycorrhizal fungus (AMF) Acaulospora mellea and three soil amendments, i.e., hydroxyapatite (HAP), manure, and biochar, at doses of 0.1% and 1% (weight:weight) to heavy metal phytoremediation using sweet sorghum grown on an abandoned agricultural soil, with environmentally realistic contamination (2.6 mg kg−1 Cd, 1796 mg kg−1 Pb, and 1603 mg kg−1 Zn), in a plant growth chamber. Mycorrhizal colonization, plant biomass and metal accumulation, metal availability, and soil pH were determined in harvested seedlings 12 weeks after sowing. The results showed that root colonization by indigenous AMF decreased by 28%-46% with HAP, but increased after manure and biochar applications as compared to the no amendment control (CK). The AMF inoculation increased root colonization rates by 16%-128% and in particular, alleviated the inhibition of HAP. The remediation effects were highly dependent on the amendment type and dose. Among the three soil amendments, HAP was the most effective in promoting plant growth and phytostabilization of Cd, Pb, and Zn and phytoextraction of Cd, particularly at a dose of 1%. Compared to CK, 1% HAP decreased DTPA-extractable Cd, Pb, and Zn concentrations in soil by 31%-43%, 30%-38%, and 22%-23%, respectively. Manure and biochar also exerted positive effects on heavy metal immobilization, as indicated by lower DTPA extractability, but only the 1% manure treatment showed plant growth-promoting effect. The AMF inoculation did not affect plant growth, but increased soil pH and induced synergistic interactions with amendments on the immobilization of Cd and Pb. In conclusion, soil amendments, particularly HAP, produced positive impacts and synergistic interactions with AMF on the phytostabilization of heavy metals using sweet sorghum. Accordingly, sweet sorghum combined with soil amendments and AMF may be an effective strategy for heavy metal phytoremediation.

The biochar-improved growth-characteristics of corn (Zea mays L.) in a 22-years old heavy-metal contaminated tropical soil

Biochar was suggested to lower the concentrations of heavy metals in contaminated soils and therefore may improve plant growth. This research was to evaluate the growth of corn (Zea mays L.) in a biochar-amended heavy-metal-contaminated tropical soil. Soil samples were collected from well-maintained experimental plots 22 years after amendment with heavy-metal containing industrial waste at 0 – 60 Mg ha-1. Corn plants were grown for 4 weeks in the soil samples amended with biochar at 0 – 10 Mg ha-1. The corn plant height and dry masses (roots, shoots, and the whole plants) were lowered by waste in relation to the increase in the soil Cu and Zn concentrations. The corn plant dry–weight masses (roots, shoots, whole plant) were well and negatively correlated with the soil Cu and Zn concentrations. The corn plant uptake of Cu and Zn decreased with the increase in the soil Cu and Zn concentration. Biochar improved the corn plant height and dry-weight masses, related to the decrease in the soil Cu and Zn concentrations. Biochar also increased the Zn uptake at waste level of ≥ 15 Mg ha-1 and increased the Cu uptake at waste level ≤ 15 Mg ha-1. The corn plant Cu uptake was linearly and positively correlated with plant dry-weight masses of roots, shoot, and whole plant masses.

Change of Mn, Ni, and Zn concentrations in soils in the city center of Kastamonu and nearby by the use of soil

Change of Mn, Ni, and Zn concentrations in soils in the city center of Kastamonu and nearby by the use of soil

Change of Mn, Ni, and Zn concentrations in soils in the city center of Kastamonu and nearby by the use of soil

Environment pollution, especially heavy metal pollution, became one of the most important problems of urban areas. Heavy metals in the air threatening human and environmental health pass to the soil after a while. Thus, soil is the medium, which can reflect the level of pollution at best. In the present study, among the heavy metals posing threat to human health, Mn, Ni, and Zn concentrations were determined in soil samples taken from 15 points, which had different characteristics, in the city center of Kastamonu province and the changes in these heavy metals by location were compared using statistical methods. As a result, it was determined that rather than anthropogenic factors, the concentrations of these heavy metals in the soil samples were shaped by the soil lithology.

Zinc in soil reflecting the intensive coal mining activities: Evidence from stable zinc isotopes analysis

In the mining area affected by coal mining activities for a long time, heavy metal Zn pollution poses a serious threat to soil quality and human health, and direct evidence showing the relationship between Zn accumulation mechanism in soils and mining activities is lacking. In this study, the Zn content and isotopes composition (δ66Zn) from soil and environmental samples around mining area were determined and analyzed to clarify the Zn characteristics in soil. Moreover, the distribution and source of Zn content in soil of mining area were analyzed by mathematical statistics, correlation analysis and isotope mass mixing model. The results showed that: (1) the Zn content in soil ranged from 95 to 327 mg·kg−1 (mean: 233 mg·kg−1), exceeding the control point and the soil background value of Anhui Province; (2) the results of Zn isotope analysis showed that Zn in soil mainly derived from the wind dispersion input of fine particles in gangue and fly ash, followed by the natural weathering of parent material; (3) isotopic mass mixing model can be used to distinguish the contribution of anthropogenic and natural Zn sources. Mining input was the main contribution source of Zn in soil (mean: 67%), followed by natural background (mean: 33%). The employment of Zn isotopes can effectively evaluate the impact of anthropogenic and natural long-term processes on Zn in the soil of the mining area, and provide important information for the formulation of soil metal pollution control measures.

Metal contamination in soils and windowsill dusts: implication of multiple sources on dust metal accumulation within a city affected by Pb smelting.

The accumulation of total Pb, Cd, Cu, and Zn in soils (0-5cm) and windowsill dust fractions (45-125, 10-45, and < 10μm), and soil pollution indices (PI), were investigated in a long-term (~ 70years) Pb smelter area and in the nearby urban city of Jiyuan, China. Principal component analysis (PCA) was utilized to identify metal contamination sources. Results showed that mean soil Pb, Cd, Cu, and Zn concentrations in the smelter area were 803, 13.8, 118, and 323mgkg-1, while those of the urban area were 270, 7.95, 51.6, and 244mgkg-1, respectively. Lead and Cd had greater soil PI than Cu and Zn. Lead concentrations in the 45-125, 10-45, and < 10-μm urban dust fractions ranged from 197.1 to 1953 (mean 1020), 202-3962 (2407), and 51.1-1258 (310.7) mg kg-1, while Cd concentrations ranged from 11.1 to 111 (49.2), 10.4-159 (64.3) and 21.5-131 (60.0) mg kg-1, respectively. Excessive Zn concentrations (5000-22,000mgkg-1) in some urban dust samples were found at two sampling sites, while Zn concentrations were < 2600mgkg-1 in all other samples. Based on PCA results, metal accumulation near the Pb smelter was dominated by smelting activities. The PCA results further suggested that mass vehicular transportation modes may be an important source of metals such as Cu and Zn in the urban area. Certain samples in both sub-areas had unsafe potential non-carcinogenic risks of Pb for children. These findings suggest that reducing environmentally relevant metal concentrations in this, and similar areas, will likely require a multi-faceted approach.

Soil Mineral Composition and Salinity Are the Main Factors Regulating the Bacterial Community Associated with the Roots of Coastal Sand Dune Halophytes.

Simple SummaryEndophytic microbes that reside in roots are involved in resistance against various environmental stresses including high soil salinity and mineral deficiency. To date, the extent of their role in the plant host adaptation to arid, saline, and low nutrient environments such as coastal sand dune ecosystems remains unclear. Here, we present the first characterization study of the bacterial community associated with the roots of Spinifex littoreus and Calotropis gigantea, two plant species that grow wild across different areas of Parangkusumo coastal sand dune, Indonesia. We correlated the bacterial composition in the root with various soil properties and found that bacterial communities in the root are responsive to changes in soil mineral composition, especially in soil Calcium (Ca), Titanium (Ti), Cuprum (Cu), and Zinc (Zn) content. Some bacteria are also found to be sensitive to soil salinity levels; among them, Bacillus idriensis has previously been reported to have a growth promoting effect on plants. Our findings provided valuable information about the main factors that modulate bacterial communities associated with coastal plants and potential bacterial species that might be involved in plant resistance against stresses. Data from this study can be used as the basis for future studies that assess the biological role of endophytic microbes in plant resistance against environmental pressure. Soil salinity and mineral deficiency are major problems in agriculture. Many studies have reported that plant-associated microbiota, particularly rhizosphere and root microbiota, play a crucial role in tolerance against salinity and mineral deficiency. Nevertheless, there are still many unknown parts of plant–microbe interaction, especially regarding their role in halophyte adaptation to coastal ecosystems. Here, we report the bacterial community associated with the roots of coastal sand dune halophytes Spinifex littoreus and Calotropis gigantea, and the soil properties that affect their composition. Strong correlations were observed between root bacterial diversity and soil mineral composition, especially with soil Calcium (Ca), Titanium (Ti), Cuprum (Cu), and Zinc (Zn) content. Soil Ti and Zn content showed a positive correlation with bacterial diversity, while soil Ca and Cu had a negative effect on bacterial diversity. A strong correlation was also found between the abundance of several bacterial species with soil salinity and mineral content, suggesting that some bacteria are responsive to changes in soil salinity and mineral content. Some of the identified bacteria, such as Bacillus idriensis and Kibdelosporangium aridum, are known to have growth-promoting effects on plants. Together, the findings of this work provided valuable information regarding bacterial communities associated with the roots of sand dune halophytes and their interactions with soil properties. Furthermore, we also identified several bacterial species that might be involved in tolerance against stresses. Further work will be focused on isolation and transplantation of these potential microbes, to validate their role in plant tolerance against stresses, not only in their native hosts but also in crops.

Root Dipping, Foliar and Soil Application of Zinc Increase Growth, Yields, and Grain Zinc in Rice (Oryza sativa L.) Grown in Moderate Zinc Soil of Inceptisol Order

ABSTRACT Zinc (Zn) fertilization not only increased yield of rice but also serves as an economical source of Zn to fight Zn deficiency problems in humans and cattle. A pot experiment was conducted during 2016 (kharif) to study the response of different methods of Zn application on growth, yield, and zinc concentration of rice. Treatments consisted of T1 – without fertilizers (WF); T2 – recommended dose of fertilizer (RDF); T3 – RDF+soil application of 5.0 kg Zn ha−1 (SA5); T4 – RDF + soil application of 7.5 kg Zn ha−1 (SA7.5); T5 – RDF + soil application of 10 kg Zn ha−1 (SA10); T6 – RDF + root dipping in 2% ZnO (RD); T7 – RDF + SA5 + RD; T8 – RDF + foliar application of 0.5% ZnSO4 at tillering and flowering stage (2FA); T9 – RDF + foliar application of 0.5% ZnSO4 at tillering, flowering, and milking stage (3FA); T10 – RDF + SA5 + foliar application of 0.5% ZnSO4 at tillering stage (1FA); T11 – RDF + SA5 + 2FA; and T12 – RDF + SA5 + 3FA. Significantly higher grain and straw yield was obtained in T7 and T6, with a corresponding increase of 17.6 and 30.0% over RDF. Conjoint application of Zn (T7) increased the Zn concentration in grain and straw as compared to RDF, but FA of Zn was more effective than SA. Higher doses of Zn applied increased Zn and manganese (Mn), but decreased the concentration of iron (Fe) and copper (Cu) in grain. Application of 10 kg Zn ha−1 (T5) significantly increased (1.78 folds) the DTPA extractable Zn content in postharvest soil over RDF.

Environmental pollution, ecological and human health risk assessment of heavy metals in rice farming system near the Buriganga River in Dhaka, Bangladesh

ABSTRACT The current study focused on quantifying hazardous heavy metals (As, Cd, Cr, Pb, Ni, and Zn) in soil-rice systems near the Buriganga River in Bangladesh to assess their impact on human health and the environment. The mean concentrations of As, Cd, Cr, Ni, and Zn in soil exceeded FAO/WHO acceptable limits, and the metal pollution index (MPI) indicated that all soil samples collected from the rice fields were severely polluted (MPI˃30) than water and rice grain samples. According to the sum of pollution index (SPI) by studied metals, rice grains collected from Kamrangirchor (29.36), Dhakauddan (28.75), and Bosila (18.08) were severely polluted. Mean Bio-concentration factors (BCFs) and Transfer factors (TFgrain/soil) in rice grains were in the following order: Cd (6.034) > Zn (1.752) > Pb (0.697) ˃ Ni (0.666) > Cr (0.135) > As (0.037), and Cd (1.150) > Zn (0.421) > Ni (0.112) ˃ Pb (0.072) > Cr (0.015) > As (0.034) respectively indicating higher accumulation of Cd in rice grain than others toxic heavy metal. The potential ecological risk index (RI) showed that except for water in Kamrangirchar and Keraniganj rice fields, all other rice fields soil and water samples did not pose severe ecological pollution (RI˂110) by different toxic heavy metals. Health risk assessment showed that rice grains are unsafe for human consumption as the carcinogenic health risk (CHR˃10-3) and non-carcinogenic health risk (HI ˃1) quotients seem more than the safe level in all samples collected from rice fields surrounding the Buriganga River. Findings show that heavy metal concentrations are high in rice fields near the Buriganga River, endangering the environment and consumer health.

Ecological Risk Evaluation and Source Identification of Heavy Metal Pollution in Urban Village Soil Based on XRF Technique

The rapid urbanization in China has resulted in significant differences between urban and rural areas. The emergence of urban villages is inevitable in this context, for which complex problems regarding land use, industrial management and ecological environment have arisen. This study performed a case study on a typical urban village, by assessing heavy metal pollution and ecological risk in soil. It detected a total of 80 basic units through portable X-ray fluorescence (XRF) instrument. A total of 25 high-risk contaminated points were selected, sampled and analyzed in laboratory as confirmation. The results showed the mean concentrations of Pb, Cu, Zn and Ni in soil were significantly higher than background values. Pb, Zn and Ni showed obvious pairwise correlation, and the high-value zones could be attributed to automobile traffic and industrial activities. In addition, the pollution problem is complicated by a combination of agricultural activities, the absence of clear division between different functional zones, as well as a general lack of environmental awareness. All of these lead to increased ecological risk and are a serios threaten to public health.

Zinc fertilization strategies in soybean: plant uptake, yield, and seed concentration

Based on the expected increase in soybean (Glycine max L.) demand and the current yield gap, smart management strategies of crop nutrition are required to improve the use of resources. Given that zinc (Zn) deficiency is the most widespread micronutrient problem in agricultural production systems, the objective of this study was to evaluate, under field conditions, the effect of different Zn fertilization strategies on seed yield, Zn uptake, and seed Zn concentration in Zn-deficient soils. To this end, a field experiment was conducted at three sites evaluating the following treatments: (i) Control = no Zn application; (ii) Seed-Zn = Zn applied to the seed (0.3 kg ha−1); (iii) Foliar-Zn = Zn foliar-applied at V5 (0.7 kg ha−1); and (iv) Soil-Zn = Zn applied to the soil at sowing (2.1 kg ha−1). At all sites, Zn fertilization significantly (p < 0.05) increased seed yield (9.5%) regardless of the fertilization strategy. The Foliar- and Soil-Zn applications generated the greatest leaf Zn concentration at R5.5 stage (60 and 50 mg kg−1, respectively). Zinc concentration in stems, pods, and the whole plant did not differ between treatments (avg. 12, 41, and 31 mg kg−1, respectively). Only Soil-Zn application increased seed Zn concentration compared to the unfertilized Control (11%). Future research on Zn dynamic in soybean should focus on: (i) recalibrating thresholds based on leaf and seed Zn concentration and (ii) evaluating different times, sources, and rates of Foliar-Zn application in reproductive stages, alone or in combination with Soil-Zn applications, to reach Zn biofortification.

An Alliance of Trifolium repens-Rhizobium leguminosarum bv. trifolii-Mycorrhizal Fungi From an Old Zn-Pb-Cd Rich Waste Heap as a Promising Tripartite System for Phytostabilization of Metal Polluted Soils.

The Bolesław waste heap in South Poland, with total soil Zn concentrations higher than 50,000 mg kg–1, 5,000 mg Pb kg–1, and 500 mg Cd kg–1, is a unique habitat for metallicolous plants, such as Trifolium repens L. The purpose of this study was to characterize the association between T. repens and its microbial symbionts, i.e., Rhizobium leguminosarum bv. trifolii and mycorrhizal fungi and to evaluate its applicability for phytostabilization of metal-polluted soils. Rhizobia originating from the nutrient-poor waste heap area showed to be efficient in plant nodulation and nitrogen fixation. They demonstrated not only potential plant growth promotion traits in vitro, but they also improved the growth of T. repens plants to a similar extent as strains from a non-polluted reference area. Our results revealed that the adaptations of T. repens to high Zn-Pb-Cd concentrations are related to the storage of metals predominantly in the roots (excluder strategy) due to nodule apoplast modifications (i.e., thickening and suberization of cell walls, vacuolar storage), and symbiosis with arbuscular mycorrhizal fungi of a substantial genetic diversity. As a result, the rhizobia-mycorrhizal fungi-T. repens association appears to be a promising tool for phytostabilization of Zn-Pb-Cd-polluted soils.

Soil properties and grape yield of vineyard as affected by sawdust addition in a semi-arid region

Due to its high organic matter content, sawdust can be used for soil amendment. This study investigated the effect of sawdust obtained from a furniture industry (Yildiz Integre Akhisar flakeboard) on grape yield and loam texture soil (Typic Xerofluvent) properties of a vineyard located in Saruhanlı District, Manisa, Turkey. In the trial, three groups with dry sawdust (10 t ha-1, 20 t ha-1; 30 t ha-1) was added to plots of vineyard while 0 t ha-1 or without sawdust addition was set up as a control group. All the 4 treatments were replicated three times (4×3). Sawdust addition resulted in significant increase (p <0.05) of soil organic matter, total nitrogen, electrical conductivity (EC), available Na, Ca, Mg, Fe, Zn, P, K, and Mn contents, moisture, saturation percentage, field capacity, wilting point, available water and aggregation percentage values compared with control group. Also, the soil pH, bulk density, and dispersion percentage significantly decreased with sawdust addition. However, there was no significant change in lime, available Cu contents, structure stability index, aggregate stability of the soil with sawdust addition. Compared with control group, addition of 20 t ha-1 and 30 t ha-1 of dry sawdust significantly increased the grape yield of the vineyard. The highest yield of 4.23 t ha-1 was recorded with 30 t ha-1 sawdust addition. Sawdust can be used as a soil amendment given its positive effects on some soil properties and grape yield of the vineyard. It is suggested that nitrogen immobilization from the soil by microorganisms due to sawdust’s high C/N ratio is a key consideration for its future use.

Global analysis of nitrogen fertilization effects on grain zinc and iron of major cereal crops.

Human zinc (Zn) and iron (Fe) deficiencies can partly be alleviated by enhancing cereal concentrations of these micronutrients. Soil nitrogen (N) levels codetermine cereal grain yields and Zn and Fe nutrition of plants and grains. Grain Zn and Fe concentrations have been reported to be affected by both yield dilution and enhanced acquisition and grain allocation of Zn and Fe. A global meta-analysis of 100 publications concerning wheat, maize, and rice providing 785 records of Zn and 506 records of Fe allowed us to assess their relative importance and quantify the concentrations and bioavailability of Zn and Fe in major cereal grains over a wide range of N fertilization levels. Compared with the no N controls, N application significantly increased grain Zn and Fe concentrations in all crops except maize Zn. The increase in grain protein concentration correlated positively with the increases in Zn and Fe concentrations in all cereals except Zn in maize. In rice, the grain Zn and Fe concentration increase was independent of the rate of N applied. Grain concentrations of Zn and Fe in wheat and Fe in maize were positively correlated with N rate but were only higher than those in the controls above 40–60 kg N ha−1. At lower N rates, the dilution effect was thus stronger than the enhancement effect. N supply had a larger effect on Zn and Fe concentrations in loamy textured soils or at lower soil available N and phosphorus (P), or higher soil organic matter and available Zn contents or with P and Zn fertilization, but the effect sizes differed among crops. Reductions in phytic acid concentration after N fertilization occurred in wheat, potentially improving micronutrient bioavailability. Thus, our findings indicate that N fertilization could be managed in ways that simultaneously support high grain yields and enhance nutritional quality for major cereals.