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Ferrous sulfate application is important in improvement of agricultural production, elimination of micronutrient deficiencies in human and animal populations, and promotion of sustainable food and feed production. This study was carried out to investigate the effects of different doses of foliar iron sulfate (FeSO4) applications on cotton plant yield and yield components, soil enzyme activity and chlorophyll content (SPAD value) and Normalized Difference Vegetation Index (NDVI) values of cotton plants. The results of both growing periods indicated that 0.4% FeSO4 application dose was more effective than the other doses compared to the control (Co), therefore, the evaluations were carried out based on 0.4% FeSO4 application dose. The application dose increased the cotton yield by 20.53 and 19.08% in the 2020 and 2021 season, respectively. The SPAD value increased by 54.88 and 98.68% in the 2020 and 2021 season. The NDVI values were 0.83 and 0.85 in the 2020 and 2021 seasons, respectively. Soil enzymes responded positively to FeSO4 application. The urease enzyme activity at this application dose varied between 17.81 and 18.76 µg N g−1 dry soil h−1 (13.73 to 26.33% increase compared to Co), and the highest value was recorded in 2021. The Dehydrogenase (DHG) enzyme activity was between 18.38 and 16.05 µg TPF g−1 dry soil 24 h−1 (39.8 and 46.30% increase compared to Co). The Catalase enzyme activity (CAT) was 36.40 and 38.73 ml O2 g−1 dm 5 min−1 in (51.23 and 39.32% compared to control) and the highest value was recorded in 2021. Nitrate Reductase Activity (NRA) was 18.66 and 17.14 µg N g−1 dm 2 h−1 in 2020 and 2021 seasons. The values of NRA were 54.11 and 59.54% lower in 2020 and 2021 seasons compared to the NRA in Co. [ABSTRACT FROM AUTHOR]

Iron (Fe) is abundant in soils but with a poor availability for plants, especially in calcareous soils. To favor its acquisition, plants develop morphological and physiological responses, mainly in their roots, known as Fe deficiency responses. In dicot plants, the regulation of these responses is not totally known, but some hormones and signaling molecules, such as auxin, ethylene, glutathione (GSH), nitric oxide (NO) and S-nitrosoglutathione (GSNO), have been involved in their activation. Most of these substances, including auxin, ethylene, GSH and NO, increase their production in Fe-deficient roots while GSNO, derived from GSH and NO, decreases its content. This paradoxical result could be explained with the increased expression and activity in Fe-deficient roots of the GSNO reductase (GSNOR) enzyme, which decomposes GSNO to oxidized glutathione (GSSG) and NH3. The fact that NO content increases while GSNO decreases in Fe-deficient roots suggests that NO and GSNO do not play the same role in the regulation of Fe deficiency responses. This review is an update of the results supporting a role for NO, GSNO and GSNOR in the regulation of Fe deficiency responses. The possible roles of NO and GSNO are discussed by taking into account their mode of action through post-translational modifications, such as S-nitrosylation, and through their interactions with the hormones auxin and ethylene, directly related to the activation of morphological and physiological responses to Fe deficiency in dicot plants. [ABSTRACT FROM AUTHOR]

Increasing multi-nutrient deficiencies and water scarcity is a major challenge for rice cultivation. In calcareous soils, nitrogen (N), iron (Fe) and zinc (Zn) deficiencies are major constraints for aerobically grown rice. Thus, a field study was conducted in factorial randomized block design with 18 treatment combinations viz. 75% recommended dose of nitrogen (RDN) through chemical nutrient source and 25% RDN through of organic sources (vermicompost or poultry manure or farm yard manure) and foliar spray with Zn and Fe at tillering and panicle initiation stage. All the growth related traits, yield attributes, yield and nutrient uptake were significantly influenced by nutrient management practices. On an average, mean grain yield was improved by 28.5% with the application of 100% RDN through chemical fertilizers + 25% RDN through vermicompost over alone 100% RDN through chemical fertilizer. Higher nitrogen uptake (100.4 kg ha−1), phosphorous (14.7 kg ha−1), potassium (95.9 kg ha−1), iron (1085.1 g ha−1) and zinc (295.1 g ha−1) were also recorded with same treatment. Application of 75% RDN through chemical fertilizer + 25% RDN through poultry manure recorded significantly higher water productivity of 0.130 US$/m3 than all other treatments while application with 100% RDN through chemical fertilizers recorded lowest water productivity of 0.091 US$/m3. The present finding indicates that under current situation of declining water resources and increasing multi-nutrient deficiencies, combined application of chemical fertilizers and poultry manure along with foliar spray of Zn and Fe will enhance the quality produce, and water productivity in aerobically grown rice in calcareous soils. [ABSTRACT FROM AUTHOR]

For optimum growth and yield production, plants need all soil minerals to be available in adequate level, and unsuitable soil conditions can restrict root's ability for uptake of minerals nutrient. For that matter, foliar sprays can be the best option for plants to benefit from nutrients. Field experiments with split-split plot design with three replications were conducted in 2018 and 2019 to determine the effects of foliar spraying zinc and iron treatments on some quality parameters of soybean (Glycine max L.) plants under calcareous soil with high pH conditions. Varieties (Arisoy, Bravo, Nazlican) were placed in main plots, growth stages of the soybean (V3, R1, R3) in sub plots and foliar fertilizers (Zn, Fe, Zn + Fe) in sub-sub plots. Foliar application of iron and zinc increased oil and protein content per soybean seed at different stages of growth in contrast to control (non-fertilizers) groups. The highest protein contents (33.61%) and oil contents (22.02%) were obtained from Zn treatment in both years. However, Zn + Fe mixture (102.25 kg da−1) was more efficient on oil yield in both years. It was observed that two-year average of polyunsaturated fatty acids was 58.93% (linoleic 50.13%; linolenic 8.80%), monounsaturated fatty acid was 24.83% (oleic), and saturated fatty acids were 14.68% (palmitic 11.82%; stearic 2.86%). Foliar Zn + Fe mixture spraying can be recommended to get high oil yield, and foliar Zn spraying for oil and protein contents from soybean based on this study. [ABSTRACT FROM AUTHOR]

The spatial variability characterization of micronutrients is needed for agricultural quality produce and environmental safety. However, study on this aspect is weakly implicit. In present study, Global Positioning System (GPS)-based 283 surface soil samples were collected and analyzed for pH, electrical conductivity (EC), organic carbon (OC), and micronutrients. Classical results revealed that soils are slightly acidic pH, safe in EC, low to medium in OC, and non-calcareous. OC was in order of Typic Haplustalfs-Chromic Haplusterts (S8)>Vertic Ustochrepts-Chromic Haplusterts (S3)>Typic Haplustalfs-Typic Haplustalfs (S9)>Typic Haplustalfs-Typic Ustipsammarts (S7)>Typic Haplusterts-Typic Ustorthents (S6)>Vertic Ustochrepts -Chromic Haplusterts (S5)> Lithic Ustochrepts -Typic Haplusterts (S4)>Typic Haplusterts -Vertic Ustochrepts(S2)>Typic Haplusterts-Typic Haplusterts (S1). In soils, zinc (Zn) and hot water-soluble boron (HWS-B) in order of S4>S5>S7>S9>S3>S2>S8>S1>S6 and S1>S2>S3>S4>S5>S9>S6>S7>S8, respectively. Overall, about 54.06 and 9.89% soil samples to be deficient in Zn and HWS-B in study area, respectively. Geo-statistical results showed that the exponential model was best-fitted for pH, calcium carbonate (CaCO3), OC, Zn and HWS-B and spherical model for EC and iron (Fe). However, the circular model was fitted for copper (Cu) and Manganese (Mn). The pH, EC, OC Zn, Cu, and Fe fall between 26 and 71%, which exhibit moderate spatial dependency. However, CaCO3 and Mn show 81 and 76% Nugget/sill ratios, respectively. Variability maps also showed the prediction of micronutrients using geo-statistical method better than classical methods. [ABSTRACT FROM AUTHOR]

In concert with oxygen, soil alkalinity strongly restricts the availability of iron, an essential nutrient with a multitude of functions in living organisms. In addition to its role in mitochondrial energy metabolism and as a cofactor for enzymes, in plants iron also plays key roles in photosynthesis and is required for chlorophyll biosynthesis. The ability to thrive in calcareous soils, referred to as calcicole behaviour, is the readout of an amalgam of traits of which efficient foraging of iron is a decisive factor. Recently, the well-established concept of two distinct iron uptake strategies, phylogenetically separating grasses from other land plants, was expanded by the discovery of auxiliary mechanisms that extend the range of edaphic conditions to which a species can adapt. Secretion of a tailor-made cocktail of iron-mobilising metabolites into the rhizosphere, the composition of which is responsive to a suite of edaphic and internal cues, allows survival in calcareous soils through a competitive iron acquisition strategy, which includes intricate interactions with the consortium of associated microorganisms in, on, and around the roots. This versatile, reciprocal plant-microbiome interplay affects iron mobilisation directly, but also collaterally by impacting growth, fitness, and health of the host. Here, we review the mechanisms and the multifaceted regulation of iron acquisition in plants, taking into consideration the specific constraints associated with the uptake of iron from alkaline soils. Knowledge on how plants extract iron from such soils sets the stage for a better understanding of essential ecological processes and for combatting iron malnutrition in humans. [ABSTRACT FROM AUTHOR]

Iron (Fe) deficiency restricts crop yields in calcareous soil. Thus, a novel Fe chelator, proline‐2′‐deoxymugineic acid (PDMA), based on the natural phytosiderophore 2′‐deoxymugineic acid (DMA), was developed to solve the Fe deficiency problem. However, the effects and mechanisms of PDMA relevant to the Fe nutrition and yield of dicots grown under field conditions require further exploration. In this study, pot and field experiments with calcareous soil were conducted to investigate the effects of PDMA on the Fe nutrition and yield of peanuts. The results demonstrated that PDMA could dissolve insoluble Fe in the rhizosphere and up‐regulate the expression of the yellow stripe‐like family gene AhYSL1 to improve the Fe nutrition of peanut plants. Moreover, the chlorosis and growth inhibition caused by Fe deficiency were significantly diminished. Notably, under field conditions, the peanut yield and kernel micronutrient contents were promoted by PDMA application. Our results indicate that PDMA promotes the dissolution of insoluble Fe and a rich supply of Fe in the rhizosphere, increasing yields through integrated improvements in soil‐plant Fe nutrition at the molecular and ecological levels. In conclusion, the efficacy of PDMA for improving the Fe nutrition and yield of peanut indicates its outstanding potential for agricultural applications. Summary Statement: Recently, a novel Fe chelator, proline‐2′‐deoxymugineic acid (PDMA), based on the natural phytosiderophore 2′‐deoxymugineic acid (DMA), was developed to correct the Fe deficiency of rice and cucumber in hydroponic culture and calcareous substrates. However, the effects and mechanisms of PDMA relevant to the Fe nutrition and yield of dicots grown under field conditions require further exploration. Our results indicate that PDMA application promotes the dissolution of insoluble Fe and a rich supply of Fe in the rhizosphere of peanut, increasing iron nutrition and yields and kernel micronutrient contents through integrated improvements in soil‐plant Fe nutrition at the molecular and ecological levels. Our results demonstrate the excellent potential of PDMA for wide use as an iron fertiliser and biostimulant in sustainable agriculture and food security. [ABSTRACT FROM AUTHOR]

Yield loss due to abiotic stress is an increasing problem in agriculture. Soybean is a major crop for the upper Midwestern United States and calcareous soils exacerbate iron deficiency for growers, resulting in substantial yield losses. Fiskeby III is a soybean variety uniquely resistant to a variety of abiotic stresses, including iron deficiency. Previous studies identified a MATE transporter (Glyma.05G001700) associated with iron stress tolerance in Fiskeby III. To understand the function of this gene in the Fiskeby III response to iron deficiency, we coupled its silencing using virus-induced gene silencing with RNAseq analyses at two timepoints. Analyses of these data confirm a role for the MATE transporter in Fiskeby III iron stress responses. Further, they reveal that Fiskeby III induces transcriptional reprogramming within 24 h of iron deficiency stress, confirming that like other soybean varieties, Fiskeby III is able to quickly respond to stress. However, Fiskeby III utilizes novel genes and pathways in its iron deficiency response. Identifying and characterizing these genes and pathways in Fiskeby III provides novel targets for improving abiotic stress tolerance in elite soybean lines. [ABSTRACT FROM AUTHOR]

Polyphosphate fertilizer is an alternative to traditional orthophosphate fertilizer, but it is unclear whether it provides greater soil phosphorus (P) mobility and availability than orthophosphate fertilizer. This study aimed to examine the chemical behaviour of polyphosphate after its application to the soil. The hydrolysis, sorption, and P transformation of two types of polyphosphate fertilizers (short‐chain and long‐chain) were examined for two types of soils (acidic Acrisol and calcareous Cambisol), with orthophosphate serving as the control treatment. 31P NMR spectroscopic analyses indicated that polyphosphate in soil was rapidly converted to pyrophosphate, which was then hydrolyzed to orthophosphate at a slower rate. In general, in the calcareous Cambisol, the addition of short‐chain polyphosphate fertilizer resulted in greater soil P mobility as measured by greater soil pore water orthophosphate concentration than the control. Thus, short‐chain polyphosphate fertilizer tended to be more effective than orthophosphate in calcareous soils. This was in contrast to the result of an aqueous incubation experiment, in which a lower pH increased the rate of polyphosphate hydrolysis. Indeed, in both soils, the sorption of total P was greater when P was added as polyphosphate than when it was added as orthophosphate. Moreover, polyphosphate sorption appeared to be mainly controlled by soil iron and aluminium minerals, because the Acrisol showed stronger polyphosphate sorption than the Cambisol due to its greater amorphous iron content. It appears that polyphosphate was first adsorbed on soil minerals before being hydrolyzed to release orthophosphate, and calcium may have played an important role in the hydrolysis of polyphosphate as evidenced by the greater P release in calcareous Cambisol. Our results suggest that soil characteristics, such as acidity, iron, aluminium, and calcium content, should be considered when evaluating the P efficiency of polyphosphate fertilizers. Highlights: 31P NMR spectroscopy successfully tracked the fate of added Poly‐P in soilPoly‐P was rapidly converted to Pyro‐P, and then hydrolyzed to Ortho‐P slowlyP supplied as Poly‐P had stronger sorption affinity than Ortho‐P in all soilsShort‐chain Poly‐P induced greater P mobility than Ortho‐P in Cambisol but not in Acrisol [ABSTRACT FROM AUTHOR]

Date palm is an important fruit for many human populations, especially in arid and semiarid regions. In addition, the fibers of the plant have the capability to remove various pollutants such as dyes, heavy metal ions, and phosphates. In the present study, micronutrients were used for enhancing various features pertaining to qualitative and quantitative aspects in date plants under the aforementioned soil. Six micronutrient levels were used as treatments, i.e. control (without micronutrients), zinc sulfate (ZnSO4), copper sulfate (CuSO4), sulfur (S), manganese sulfate (MnSO4), and iron chelate (Fe). According to the results of the combined analysis, the effects of micronutrients were significant on fruit yield (FY), 10 seeds mass (TSM), fruit diameter (FD), fruit length (FL), seed diameter (SD), and sucrose (P <.05). The results demonstrated that iron (Fe) significantly enhanced the FY, FD, FL, TSM in comparison with the control. Based on the cluster analysis, the Fe treatment separated from the other treatments, indicating the extent of difference that this treatment had on the plants in comparison with other treatments. Finally, the results suggested that the application of Fe could improve several features of date palm fruits, especially the FY in the said soils. [ABSTRACT FROM AUTHOR]

Plants need all plant nutrition elements to be available and adequate level in soil for optimum growth and yield production. The uptake of macro and micro nutrients by plants is limited or they can not be beneficial for plants in calcareous soils with high pH such as being in Mediterranean Region. In such situations, management strategies such as foliar spray can be useful to benefit of plants from them particularly under soil-limed condition with restricted micronutrients uptake. In this study, it was aimed to evaluate the effects of foliar-applied zinc and iron on chlorophyll content, leaf area index (LAI) and chemical composition of soybean (Glycine max L.) at different growth stages. Field experiments were conducted over during the second crop seasons of the years 2018 and 2019 under the conditions of Hatay Province. The experiment was designed as split-split plot design with three replications. Varieties (Arısoy, Bravo, Nazlıcan) were placed in main plots, growth stages (V3, R1, R3) in subplots and foliar fertilizers (control, zinc, iron, zinc + iron) in sub-sub-plots. Foliar application of iron and zinc increased chlorophyll content and LAI values at different stages of growth in contrast to control (untreated) groups. The highest SPAD value (36.03) was obtained from Nazlıcan × R3 × Zn + Fe treatment and the highest LAI (7.57) was obtained from Bravo × V3 × Fe treatment. Generally, the higher results of SPAD value were observed in reproductive stages while the higher results of LAI were observed in vegetative stages. Leaf zinc and iron accumulations were higher in reproductive stages. As a result of this study, it was observed that micro nutrients needed by soybean plant can be supplied with foliar applications in calcareous soils. [ABSTRACT FROM AUTHOR]

Iron (Fe) deficiency is a major nutritional disorder in crops growing in calcareous soils. Varagu crop are more susceptible to (Fe) deficiency in the early stage of growth and the deficiency is exhibited as chlorosis developing interveinally in the new leaves. The objective of the present study was to see the impact of different levels iron on mitigation of chlorosis in varagu, Paspalum scrobiculatum under calcareous soil and to investigate the influence of soil and foliar application of iron on growth, physiological and improvement of yield potential of varagu under calcareous soil condition. The varagu variety CO3 taken for this study The treatments comprised T1, NPK (44:22:0 kg ha-1) + 12.5 t FYM/ha,T2, NPK (44:22:30 kg ha-1) +12.5 t FYM/ha, T3, T1 + Soil application of FeSO4 (25 kg ha-1), T4, T2 + Soil application of FeSO4 (25 kg ha-1), T5, T1 + Soil application of FeSO4 (50 kg ha-1), T6, T2 + Soil application of FeSO4 (50 kg ha-1), T7, T3 + Foliar spray of 0.5% FeSO4, T8, T4 + Foliar spray of 0.5% FeSO4, T9,T5 + Foliar spray of 0.5% FeSO4, T10, T6 + Foliar spray of 0.5% FeSO4. During experimentation, morphological characteristics, growth attributes, physiological and biochemical components and biomass traits determined the mitigation of iron chlorosis. The iron deficiency in varagu was effectively controlled by T10, soil treatment 50 kg ha-1 FeSO4 and foliar spray of 0.5% FeSO4 applied on the 30th and 50th days after sowing through maintaining highest growth parameter values, maximum catalase and peroxidase activity and maintaining more chlorophyll content. [ABSTRACT FROM AUTHOR]

The most effective agricultural practice to prevent iron deficiency in calcareous soils is fertilizing with synthetic chelates. These compounds are non-biodegradable, and persistent in the environment; hence, there is a risk of leaching metals into the soil horizon. To tackle iron deficiency-induced chlorosis (IDC) in crops grown on calcareous soils, environmentally friendly solutions are needed rather than chemical application as it affects the soil health further. Hence, the present work focused on isolating and screening calcareous soil-specific bacteria capable of producing iron-chelating siderophores. Siderophore-producing bacteria (SPB) was isolated from the groundnut (Arachis hypogea L.) rhizosphere region, collected from Coimbatore district, Tamil Nadu, of which 17 bacterial isolates were positive for siderophore production assayed by chrome azurol sulphonate. The performance of SPB isolates was compared for siderophore kinetics, level of siderophore production, type of siderophore produced and iron-chelating capacity under 15 mM KHCO3. Four best performing isolates were screened, with average siderophores yield ranging ∼60–80% under pH 8, with sucrose as carbon source and NH2SO4 as nitrogen source at 37 °C. The four efficient SPB were molecularly identified as B. licheniformis, B. subtilis, B. licheniformis, and O. grignonense based on 16S rDNA sequencing. The simultaneous inhibition method showed T.viride has the highest antagonistic effect against S.rolfsii, and M.phaseolina with a reduction of mycelial growth by 69.3 and 65.1%, respectively, compared to control. Our results indicate that the optimized conditions enhanced siderophores chelation by suppressing the stem and root rot fungi, which could help in a cost-effective and environmentally friendly manner. [ABSTRACT FROM AUTHOR]

Tomato (Solanum lycopersicum L.), grown in iron deficient and calcareous soils, exhibits poor growth and yield loss, which may be moderated using biostimulants. A field experiment was conducted to determine the efficacy of the application of iron glutamate (Fe-Glu), iron sulfate (FeSO4), and L-glutamate (Glu) on growth and yield performance. Foliar application included: no treatment (NS), 0.50% FeSO4, 1% FeSO4, 0.50% Fe-Glu, 1% Fe-Glu, 0.50% L-Glu, or 1% L-Glu. Foliar application of 1% Fe-Glu increased plant height by 31%, shoot fresh weight by 25%, root fresh weight by 38%, and canopy diameter by 23%. Exogenous application with 1% Fe-Glu improved the fruit count and overall yield by 57% and 44%, respectively. There was an increase in fruit length by 20% and an increase in fruit diameter by 25%, respectively, due to foliar application of 1% Fe-Glu. Use of 1% Fe-Glu foliar might act as a better biostimulant than conventional sulfate salts in increasing tomato crop performance. [ABSTRACT FROM AUTHOR]

Iron is an essential micronutrient for living organisms, but its solubility is extremely low under alkaline conditions. Plants often suffer from iron deficiency chlorosis in calcareous soils, which consist of approximately 30% of the world's cultivated area, severely limiting plant productivity. Iron deficiency anemia is also a widespread problem in humans, especially in Asian and African people who take up iron mainly from staple foods containing low iron concentrations. Transgenic manipulation of genes involved in plant iron uptake, translocation, and storage has made improvements in enhancing iron deficiency tolerance or iron accumulation in edible parts, but these two properties have been characterized separately. We previously produced transgenic rice lines, with concomitant improvement of iron deficiency tolerance and grain iron accumulation by knocking-down OsHRZ ubiquitin ligases, which negatively regulate iron deficiency response and iron accumulation in rice. In the present report, we aimed to further improve the iron deficiency tolerance and grain iron accumulation of OsHRZ knockdown rice by the simultaneous introduction of the engineered ferric-chelate reductase gene Refre1/372 under the control of the OsIRT1 promoter for further enhancement of iron uptake. We obtained several transgenic rice lines with repressed OsHRZ expression and induced Refre1/372 expression. These lines showed a variable degree of iron deficiency tolerance in calcareous soils, with increased iron accumulation in brown seeds under both iron-deficient and iron-sufficient soil cultures. Selected OsHRZ knockdown plus Refre1/372 lines showed similar or better growth compared with that of singly introduced OsHRZ knockdown or Refre1/372 lines in calcareous soils under both non-submerged and submerged conditions. After submerged calcareous soil cultivation, these OsHRZ knockdown plus Refre1/372 lines accumulated 2.5–4.3 times and 17–23 times more iron concentrations than that of non-transformants in brown rice and straw, respectively, which was comparable or superior to a single OsHRZ knockdown line. Our results indicate that the combined introduction of OsHRZ knockdown and OsIRT1 promoter-Refre1/372 is highly effective in further improving the iron deficiency tolerance without compromising the iron accumulation of the OsHRZ knockdown effects. [ABSTRACT FROM AUTHOR]

SUMMARY: Iron deficiency is a major constraint for plant growth in calcareous soils. The interplay between NO3− and Fe nutrition affects plant performance under Fe‐deficient conditions. However, how NO3− negatively regulates Fe nutrition at the molecular level in plants remains elusive. Here, we showed that the key nitrate transporter NRT1.1 in Arabidopsis plants, especially in the shoots, was markedly downregulated at post‐translational levels by Fe deficiency. However, loss of NRT1.1 function alleviated Fe deficiency chlorosis, suggesting that downregulation of NRT1.1 by Fe deficiency favors plant tolerance to Fe deficiency. Further analysis showed that although disruption of NRT1.1 did not alter Fe levels in both the shoots and roots, it improved the reutilization of apoplastic Fe in shoots but not in roots. In addition, disruption of NRT1.1 prevented Fe deficiency‐induced apoplastic alkalization in shoots by inhibiting apoplastic H+ depletion via NO3− uptake. In vitro analysis showed that reduced pH facilitates release of cell wall‐bound Fe. Thus, foliar spray with an acidic buffer promoted the reutilization of Fe in the leaf apoplast to enhance plant tolerance to Fe deficiency, while the opposite was true for the foliar spray with a neutral buffer. Thus, downregulation of the shoot‐part function of NRT1.1 prevents apoplastic alkalization to ensure the reutilization of apoplastic Fe under Fe‐deficient conditions. Our findings may provide a basis for elucidating the link between N and Fe nutrition in plants and insight to scrutinize the relevance of shoot‐expressed NRT1.1 to the plant response to stress. [ABSTRACT FROM AUTHOR]

Iron deficiency, which severely decreases the plant yield and quality, is one of the major problems of calcareous soils. Foliar applications of humic substances and/or Fe fertilizers are environmentally friendly methods to cope with Fe deficiency. The aim of this study was to investigate the combined effect of Fe/nano Fe and humic/fulvic acid-based biostimulant foliar applications on the Fe content and plant growth parameters of spinach. Treatment solutions were prepared either by mixing a common Fe fertilizer, FeSO4·7H2O, with different commercial biostimulants (Fulvic-based: Fulvagra®, Fulvagra®WSG; Humic-based: HS300®, Humin Fe® and Liqhumus®, Grevenbroich, Germany) or by mixing nano ferrihydrite with different ratios of fulvic substance (FA-50, FA-75, and FA-100) and humic acid (Nano Iron). Growth parameters (plant fresh and dry weights, plant dry matter, root fresh and dry weights, root dry matter, leaf number per plant, and leaf area); chlorophyll reading value (SPAD); chlorophyll (a,b, and total) and carotenoid contents; and leaf and root mineral contents (N, P, K, Ca, Mg, S, Cu, Mn, Zn, B, active Fe, and total Fe) of samples were determined. Our results showed that foliar application of biostimulants together with Fe sources improved the nutrient uptake, chlorophyll contents, growth characteristics, and yield; however, not all humic substances had the same effect. When all parameters were considered, Fulvagra treatment—which contained 17% fulvic acid and microorganisms in its content together with 20 mM FeSO4·7H2O—was the most effective application, followed by FA100 treatment containing fulvic acid and 20 mM nano ferrihydrite. This finding indicates that fulvic acid containing biostimulants is more effective in foliar applications than humic-based biostimulants against Fe deficiency due to their low molecular weight which enables better penetration into the leaves. In conclusion, foliar applications of fulvic substances together with Fe fertilizers can be used to increase the Fe uptake of crops and the yields under Fe-deficient conditions. [ABSTRACT FROM AUTHOR]

One of the problems of calcareous soils is the lack of absorbable iron for plants grown in these areas. Research by various researchers has shown that some rhizosphere-dwelling microorganisms have the ability to solubilize resources containing low-soluble iron and conversion it to soluble and absorbable for the plants. Different mechanisms such as proton secretion, production of organic acids, and production of siderophore can be effective in solubilizing low-soluble iron. Accordingly, in this study, the potential of twenty rhizobacteria for solubilizing low-soluble iron sources (eg, iron phosphate, hematite, and goethite) has been evaluated. The experiment was performed under in-vitro condition in a completely randomized design with three replications. According to the results, three isolates, namely, ZP15, ZC10, and ZP13 were characterized as promising isolates. In the presence of iron phosphate, the concentration of solubilized iron by isolates ZP15, ZP13, and ZC10 was 5.19, 4.35, and 4.27 mg/l, respectively. These values for the isolates ZC10 and ZP13 in the presence of hematite was recorded 6.49 and 5.35 mg/l, respectively, and in the presence of goethite was 7.02 and 6.70 mg/l, respectively. The amount of siderophore production for the three isolates ZP15, ZC10, and ZP13 was 16.47, 17.1, and 31.55 µM, respectively. The high-performance liquid chromatography analysis revealed that the most important acids produced by these isolates were 2-ketogluconic acid (303.8 µg/ml) for ZP15, oxalic acid (246.9 µg/ml) for ZC10, and gluconic acid (100.2 µg/ml) for ZP13, respectively. The molecular and biochemical identification of these three isolates ZP15, ZC10, and ZP13 showed that they belong to the genera Stenotrophomonas, Pantoea, and Agromyces, respectively. [ABSTRACT FROM AUTHOR]

Water and iron are crucial elements for soybean growth and development, particularly in calcareous soils and arid climatic conditions. The aim of this study was to improve iron and water use efficiency and enhance soybean resilience to water scarcity and iron deficiency. So, the effect of 16 treatments; 4 deficit irrigation water regimes (25, 50, 75 and 100 % crop water requirements (CWR)) combined to 4 foliar iron gradual concentrations (F0=0, F1=1, F2=3 and F3=5 g/L of FeSO 4) applied at 3–4 leaves, at the beginning of flowering and at the end of flowering; was investigated in this split plot experiment with 4 replicates. Our results showed that supplying iron and water to plants can improve chlorophyll florescence a, chlorophyll content, stomatal conductance, yield, iron uptake, and protein content. Determining the optimal combination of deficit irrigation treatment and gradual iron sulfate concentrations for soybean is an alternative to save water and improve growth parameters. In our manuscript, we can conclude that 75 % CWR × F2 is the best combination of the two factors that led to the same biological yield as 100 % CWR. Consequently, we can say that applying F2 as a foliar iron concentration led to an economy of 25 % of the soybean crop water requirement by ensuring an adequate supply of soluble iron, facilitating root uptake, promoting protein synthesis, enhancing chlorophyll formation, and supporting overall nutrient uptake and metabolism. • Supplying water and iron to soybeans can improve chlorophyll florescence a and chlorophyll content. • Deficit irrigation and gradual iron sulfate treatments in soybeans saves water and boosts growth. • Applying F2=3 g/L as foliar iron concentration saves 25 % of soybean crop water requirements (CWR). • 75 % CWR*F2 is the best combination that led to the same biological yield as 100 % CWR. • Adequate supply of water and iron facilitates root nutrient uptake and promotes protein synthesis. [ABSTRACT FROM AUTHOR]

In the last decade, annona crop was introduced to Lebanon. This experiment was conducted to enhance the adaptation of annona to local conditions. Three scion/rootstock combinations were obtained from self– and cross– cleft grafting of Annona squamosa (Sq) and Annona cherimola (Ch), planted in calcareous “white soil” and clay–loamy “red soil”, and fertilized or not by iron (Fe) through fertigation. In the third year, the treatment red soil–iron fertilization–Sq/Ch had significantly highest plant height, trunk diameter, leaf number, number of primary roots, fruit number and yield. In the third year, despite iron fertilization, plants of the three graft combinations cultivated in red soil had higher flower number, fruit number, individual fruits weight and yield, than those planted in white soil. In the same year, iron fertilization in white soil had only affected total dry mass, leaf mass fraction and leaf iron content. However, iron fertilization of Sq/Ch planted in red soil has improved leaf number, primary root number, primary root length, leaf chlorophyll index, and leaf iron content compared to non–fertilized plants. Conclusively, iron fertilization in red soil could be a useful method improving the performance and yielding capacity of annona crop mainly in Sq/Ch combination. [ABSTRACT FROM AUTHOR]

Manganese (Mn) and iron (Fe) are the two vital micronutrients for plants and moreover essential nutritional health components in humans. Iron deficiency is common in humans and causes many health issues. In this survey, wheat grains of two major wheat cultivars were analyzed for their Mn and Fe concentrations beside the natural gradient of micronutrient availability across Sulaymaniyah province, Iraqi Kurdistan. However only 20% and 7.5% of the soils samples were Mn and Fe deficient or below recommended level. The considered micronutrient concentrations in the grains of wheat were in the acceptable range which are reported globally (range 41.3 and 37.6 mg kg-1 respectively). Furthermore, high application of nitrogen and phosphorus fertilizer in the studied calcareous soils could be strongly affected on the studied micronutrients concentration in the studied grain samples. The results indicate that adequate levels of Mn and Fe in the surveyed grains is a beneficial guide for quality of grains associated with human healthiness, where wheat grain bread is an essential food. [ABSTRACT FROM AUTHOR]

The investigation of the adaptive strategies of wild plant species to extreme environments is a challenging issue, which favors the identification of new traits for plant resilience. We investigated different traits which characterize the root-soil interaction of Parietaria judaica , a wild plant species commonly known as "Pellitory-of-the-wall". P. judaica adopts the acidification-reduction strategy (Strategy I) for iron (Fe) acquisition from soil, and it can complete its life cycle in highly calcareous environments without any symptoms of chlorosis. In a field-to-lab approach, the microbiome associated with P. judaica roots was analyzed in spontaneous plants harvested from an urban environment consisting in an extremely calcareous habitat. Also, the phenolics and carboxylates content and root plasticity and exudation were analyzed in P. judaica plants grown under three different controlled conditions mimicking the effect of calcareous environments on Fe availability: results show that P. judaica differentially modulates root plasticity under different Fe availability-impaired conditions, and that it induces, to a high extent, the exudation of caffeoylquinic acid derivatives under calcareous conditions, positively impacting Fe solubility. • Understanding plant resilience to various natural habitats and climate changes is an emerging and urgent goal. • The root plasticity, exudation and microbiome associated in Parietaria Judaica, a calcicole wild plant, has been studied. • P. judaica differentially modulates root plasticity under direct Fe deficiency when compared to calcareous and alkaline conditions. • P. judaica induces the exudation of caffeoylquinic acid derivatives under calcareous conditions impacting Fe solubility. [ABSTRACT FROM AUTHOR]

Purpose: Evaluation of various mechanisms of Cd2+ and Zn2+ root uptake through modelling, including interactions with Fe uptake. Methods: Four increasingly complex models were developed and tested against measured uptake by the hyperaccumulator Noccaea caerulescens grown on three contaminated soils. Model 1 formalises root uptake of free hydrated ions only, to which the dissociation of soil-borne metal complexes was added in Model 2, together with the root uptake of these complexes through the Fe pathway in Model 3. Model 4 represents Strategy I for Fe uptake, with Cd2+ and Zn2+ complexed by a root organic exudate hijacking the Fe adsorption/reduction pathway. Results: Model 1 enables a good prediction of Cd and Zn uptake in acidic or neutral soils. In contrast, the high Cd uptake in the alkaline soil cannot be reached either by simulating additionnally the dissociation of Cd complexes with soil-borne ligands (Model 2), nor by replicating their uptake through the Fe pathway (Model 3). These results suggest that the plant increases the Cd availability in alkaline soil during the uptake process. Supporting this idea, the uptake of Cd desorbed from iron hydroxide and calcium carbonate by root exuded ligands for Fe acquisition (simulated in Model 4) can explain the high Cd uptake from alkaline soil. Conclusions: In acid soils, Cd and Zn uptake can be predicted from their free hydrated concentrations, while in calcareous soils with very low concentrations of free hydrated ions, root exudation for Fe acquisition could make other soil Cd species phytoavailable. [ABSTRACT FROM AUTHOR]

Development of alleviation strategies, which enhance plant growth under heavy metal stress, is important. Inorganic (zeolite) and organic (diethylene triamine penta‐acetic acid, DTPA) amendments affecting the alleviation of lead (Pb) stress in a calcareous soil were tested by investigating leaf nutrient uptake of tomato (Lycopersicon esculentum L.) plants.Experimental quantities of lead (Pb) at 0, 50, 100 and 150 mg·kg−1 soil, zeolite (clinoptilolite) at 0%, 0.5% and 1%, and DTPA at 0, 50 and 100 mg·kg−1 soil were tested in a factorial experiment with three plant replicates.According to the anova, Pb, zeolite, DTPA and their interactions significantly affected plant concentrations of nitrogen (N), potassium (K), iron (Fe), zinc (Zn), copper (Cu), manganese (Mn) and lead (Pb). With increasing DTPA concentration at different levels of zeolite and Pb, plant concentrations of macro‐ and micronutrients significantly increased. Increasing soil Pb increased leaf Pb concentration and decreased the uptake of N, K, Fe, Zn, Cu and Mn. Although with increasing Pb concentration the uptake of macro‐ and micronutrients decreased in tomato, the use of zeolite and DTPA alleviated this stress by increasing nutrient uptake compared to the control. Interestingly, however, increased levels of zeolite and DTPA led to a decreased uptake of nutrients by plants (compared with control), indicating the absorption of such nutrients by the two amendments and their partial release for further plant use.Zeolite and DTPA may alleviate the negative effects of soil Pb on tomato growth by decreasing nutrient leaching and increasing plant nutrient uptake. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to study the interaction effects of phosphorus and copper on wheat. The soils used were calcareous loamy sand (ls) and non calcareous sandy loam (sl). Four levels of Cu (0, 5, 10 and 20 mg Cu kg−1 soil) and six levels of P (0, 25, 50, 100, 200 and 400 mg P kg−1 soil) were applied in all possible combinations with three replications. Soil pH decreased with Cu application while Olsen P increased with P application in both soils. Growth and yield of wheat improved significantly with graded levels of applied P. However, when any level of P was combined with 20 mg Cu kg−1 soil, severe iron chlorosis of leaves, a drastic reduction in growth and chlorophyll content was observed in calcareous ls only. The results indicated that it was Cu and not P that induced Fe deficiency in wheat grown in alkaline calcareous soil and the Cu requirement of the crop seemed to be much lower in the calcareous ls. Root dry matter, grain and straw yield decreased with increasing levels of applied Cu in ls but in sl maximum increase of 62.5, 74.3 and 63.7 per cent in root, grain and straw yield was observed with a combined application of 400 mg P and 5 mg Cu kg−1 soil over control. Accumulation of Cu in roots decreased the Fe absorption by roots which indicated that Fe chlorosis of wheat leaves is expected when Cu: Fe concentration ratio in root is > 0.30. [ABSTRACT FROM AUTHOR]

Iron availability in alkaline and calcareous soils is very much limited due to high pH and presence of the excess amount of carbonate and bicarbonate ions. Iron is though adequately present in soils, it is not always sufficiently available to plants due to their faster conversion into unavailable ferric (Fe3+) forms. The present study was taken up to understand the availability of Fe in soils and its relationship with various soil properties. A laboratory experiment was conducted with two calcareous soils and a noncalcareous soil and incubated for 45 days with various levels (0, 5 and10 kg Fe ha-1) and sources of Fe (FeSO4 and Fe EDTA) on calcareous and noncalcareous soils. The results revealed that increasing levels of Fe either as FeSO4 or Fe EDTA increased the availability in soils and higher availability was noted with the application of 10 kg Fe EDTA in all the three soils. A linear increase in the Fe availability was observed with the addition of Fe EDTA at 10 kg ha-1 up to 45 days while with the addition of 50 kg FeSO4 ha-1 higher availability was noticed up to 30 days after incubation. Inclusion of amendments viz., 12.5 t FYM and 0.25% Acetic acid though further improved the availability in all soils, the effect was much better with FYM than the acetic acid in calcareous soils than in noncalcareous soil. A strong negative correlation was observed between soil pH and calcareousness with DTPA Fe availability. [ABSTRACT FROM AUTHOR]

A field study was conducted to assess the effect of two levels each of Fe (2.5 and 5.0 kg ha-1) and Mo (1.0 and 2.0 kg ha-1) applied alone or in combination on nodulation, nitrogen fixation, fresh pods yield and nutrient uptake of pea [Pisum sativum L.] under silt-loam alkaline soil conditions. Treatments were arranged in randomized complete block design (RCBD) with three replications. The required Fe and Mo as [(NH4)6Mo7O244H2O] and FeSO4.7H2O respectively were applied to soil followed by thorough mixing before sowing. Both Fe and Mo induced significant increases in fresh pods pea yield and nutrient uptake. Their combined effect was more prominent than their alone application. The maximum fresh pods yield of 5458 kg ha-1 and biomass yield of 10315 kg ha-1 were obtained with the combine application of high levels of Mo and Fe (2 and 5 kg ha-1) and has also enhanced nodules number by 152 %, fresh weight of nodules by 135 %, N concentration in plant by 29 %, N uptake by 50 %, N2 fixation by 85 % over the control. Application of Mo and Fe at all levels alone or in combinations also improved soil organic matter, mineral N, P and K status that could be associated with more N2 fixation, enhanced plant and root growths of plants. These results suggested that application of both Mo and Fe is necessary for pea crop enhanced nodulation, N2 fixation, yield, nutrient uptake and for improved soil fertility. [ABSTRACT FROM AUTHOR]

The accumulation of reactive oxygen species (ROS) leads to oxidative damage; however, ROS also acts as signaling molecules. We previously demonstrated that the inducible silencing of thylakoid membrane-bound ascorbate peroxidase Arabidopsis plants (IS-tAPX) accumulated H 2 O 2 in their chloroplasts, resulting in the clarification of ROS-responsive genes. In IS-tAPX plants, the transcript levels of the basic helix-loop-helix (bHLH) transcription factor bHLH101, which belongs to clade Ib bHLH, were down-regulated. In order to investigate the participation of bHLH101 in chloroplastic H 2 O 2 -mediated signaling, we isolated dominant negative expression mutants of bHLH101 ( DN-bHLH101 ). DN-bHLH101 plants showed a significant phenotype that was sensitive to a methylviologen treatment, even under iron-sufficient conditions. Furthermore, the knock out mutant of bHLH101 showed a photo-oxidative sensitive phenotype, indicating that other clade Ib bHLHs do not compensate for the function of bHLH101. Thus, bHLH101 appears to act as a regulatory component in photo-oxidative stress responses. We also found that ferric chelate reductase activity was stronger in IS-tAPX plants than in control plants, suggesting that there is a close relationship between iron metabolism and oxidative stress responses. [ABSTRACT FROM AUTHOR]

Natural concentrations of trace elements are necessary for assessing trace elements contamination affected by anthropogenic activities in soils. This study was conducted to establish background concentrations of cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn) in 50 unpolluted native soils with a total of 100 soil samples (surface and subsurface soil layers) in Hamedan province of Iran. Different methods have been used for the evaluation of background limits, and the relationships between soil properties and trace elements concentrations and among trace element concentrations have been analyzed. Values from Geometric Mean (GM) procedure had the lowest background limit, while the GM × GSD 2 (geometric standard deviation) method produces the highest background limits. The percentage of outliers in Median + 2MAD (median absolute deviation) ranged from 4.0 to 16.0% for natural data and from 0.0 to 12% for log-transformed data. The smallest outlier percentage was for Cd and Cr, and it was higher for Co, Cu, and Zn. The obtained geochemical baseline concentrations (mg kg −1 ) based on Median + 2MAD were (log-transformed data) Cd 1.36, Co 15.42, Cr (natural data) 36.69, Cu 29.99, Fe 25.79 (g kg −1 ), Mn 368.68, Ni (natural data) 53.59, Pb 39.60, Zn 103.80. Carbonate calcium had significant negative correlations with Co, Cr, Cu, Fe, and Mn, indicating that trace elements are not included in the crystal structure of secondary carbonate minerals; consequently, accumulation of CaCO 3 causes a dilution effect in the soils. The content of clay, silt and organic matter had significant role in the accumulation of Mn, Ni, and Pb in the soils of the studied area. Significant correlation was found among Co, Cr, Cu, Fe, Mn, and Ni and between Zn with Cd, Cr, Cu, Mn, and Ni. Factor analysis of trace elements explored six factors attributing 64.1% of the total variability. According to the results found by upper whisker method, correlation analysis and factor analysis, studied trace elements contaminated none of the soil samples, natural accumulation processes influenced their contents in soils and origin of trace elements may be lithogenic, but their sources may be different. [ABSTRACT FROM AUTHOR]

A two-year experiment was conducted in an iron(Fe)-deficient orchard with calcareous soil to find out an alternate method for soil application of Fe ethylenediamine-N,N'-bis(2-hydroxyphenylacetic acid) (Fe-EDDHA) in orange trees. Foliar sprays of Fe-EDDHA (5 g l−1, pH = 7.8), sulfuric acid (pH = 3), citric acid (5 g l−1, pH = 2.4), Fe (II) sulfate solutions (250, 500, and 750 mg Fe l−1) with their initial pH (6.5, 6.35, and 6.12) and reduced ones to pH of 3 were compared with soil applied (75 g tree−1) Fe-EDDHA and a control test. Although optimum chlorophyll content, leaf Fe concentration, fruit quantitative and qualitative attributes were resulted from soil application of Fe-EDDHA, repeated sprays of Fe-EDDHA or acidified Fe solutions created suitable results. Acidification of Fe solutions made them more effective in alleviation of leaf Fe concentration and Fe chlorosis, probably due to remobilization of inactive Fe within the plant and prevention of Fe oxidation and precipitation in foliar solutions. [ABSTRACT FROM AUTHOR]

Background and aims: Iron (Fe) is an essential micronutrient for all higher organisms. Fe is sparingly available in calcareous soils and Fe deficiency is a major agricultural problem worldwide. Nicotianamine (NA) is a metal chelator involved in metal translocation in plants. Sweet potato is an attractive crop that can grow in poor soil and thus is useful for planting in uncultivated soil. In addition, the sweet potato has recently been suggested as a source of bioethanol. Our aim is to increase NA concentration in sweet potato to ameliorate Fe deficiency. Method: Sweet potato plants expressing the barley NA synthase 1 ( HvNAS1) gene under the control of CaMV 35S promoter were produced by Agrobacterium-mediated transformation. Results: The transgenic sweet potato exhibited tolerance to low Fe availability when grown in calcareous soil. The level of tolerance to low Fe availability was positively correlated with the HvNAS1 expression level. The NA concentration of the transgenic sweet potato leaves was up to 7.9-fold greater than that of the non-transgenic (NT) plant leaves. Furthermore, the Fe and zinc concentrations were 3- and 2.9-fold greater, respectively, in transgenic sweet potato than in NT plant leaves. Conclusions: Our results suggest that increasing the NA concentration of sweet potato by overexpression of HvNAS1 could significantly improve agricultural productivity and energy source. [ABSTRACT FROM AUTHOR]

Iron (Fe) deficiency is a critical agricultural problem, especially in calcareous soil, which is distributed worldwide. Rice plants take up Fe(II) from soil through a OsIRT1 transporter (Strategy I-related system) and also take up Fe(III) via a phytosiderophore-based system (Strategy II system). However, rice plants are susceptible to low-Fe conditions because they have low Fe(III) reduction activity and low-level phytosiderophore secretion. Previously, we produced transgenic rice plants expressing a mutationally reconstructed yeast ferric chelate reductase, refre1/372, under the control of the OsIRT1 promoter. This transgenic rice line exhibited higher Fe(III) chelate reductase activity and tolerance to Fe deficiency. In addition, we produced transgenic rice overexpressing the Fe deficiency-inducible transcription factor, OsIRO2, which regulates the expression of various genes involved in the strategy II Fe(III) uptake system, including OsNAS1, OsNAAT1, OsDMAS1, OsYSL15, and TOM1. This transgenic rice exhibited improved phytosiderophore secretion ability and tolerance to Fe deficiency. In the present research, transgenic rice plants that possess both the OsIRT1 promoter-refre1/372 and the 35S promoter-OsIRO2 (RI lines) were produced to enhance both Strategy I Fe(II) reductase ability and Strategy II phytosiderophore productivity. RI lines exhibited enhanced tolerance to Fe-deficient conditions at the early and middle-late stages of growth in calcareous soil, compared to both the non-transgenic line and lines harboring either OsIRT1 promoter-refre1/372 or 35S promoter-OsIRO2 alone. RI lines also exhibited a 9-fold higher yield than the non-transgenic line. Moreover, we successfully produced Fe-deficiency-tolerant Tachisugata rice, which is a high-biomass variety used as fodder. Collectively, our results demonstrate that combined enhancement of two Fe uptake systems in rice is highly effective in conferring tolerance to low Fe availability in calcareous soil. [ABSTRACT FROM AUTHOR]

A small collection of echinoderm holdfasts from the Ludlow Cardiola Formation of the Carnic Alps (Austria) contains a wide range of morphologies as a response of environmental adaptation. In general, the holdfasts have a globous and massive dome-like profile with several processes arranged in a sub-radial disposition, so to create a sort of 'star-like' outline. A small central depression is common but not present on all specimens. The distinctive holdfasts are preserved in an iron-rich phase, documenting a substitution that has also affected other non-echinoderm calcareous material. [ABSTRACT FROM AUTHOR]

Laboratory experiment was carried out in order to study the adsorption of Fe as FeEDDHA as related to some soil properties in six calcareous soils from the middle of Iraq. Langmuir, Freundlich and Temkin equations were used for describing Fe adsorption. The best equation was chosen according to highest value of r, r2 and t and least value of Standard error of estimate. The results showed that Freunglich equation was more efficient for describing Fe sorption compared with other physicochemical equations used, depending on highest values of, r (0.985), r 2 (0.970) and t ( 20.01) and lower standard error SE.e (0.186). Maximum adsorption capacity in tested soils were 415.2, 393.7, 353.7, 344.2, 318.4 and 306.0 µg Fe g-1 soil while the binding strength were 0.059, 0.046, 0.059, 0.051, 0.059 and 0.064 ml Fe µg-1 for Balad, Al-Khalis, Al-Raaid, Al-Wehda, Al-Mussayib and Al-Rashidaaa. 59.2% of the applied Fe was sorbed on soil while 40.8% remained soluble in soil solution. Freunglich adsorption constants (lnKf and 1/n) significantly correlated with Langmuir maximum adsorption (b) and binding strength (K). Also, the maximum adsorptive capacity (b) of Langmuir models statistically related to soil properties (EC, total and active carbonate and plant available Fe). It can be concluded from this study that Freunglich and Langmuir equations were more suitable for describing Fe adsorption in all tested soils. Tested soils sorbed Fe according to the following arrangement: Balad > Al-Khalis > Al-Raaid > Al-Wehda > Al-Mussayib > Al-Rashidaa. [ABSTRACT FROM AUTHOR]

Despite the high abundance of iron (Fe) in most earth's soils, Fe is the major limiting factor for plant growth and development due to its low bioavailability. With an increasing recognition that soil microbes play important roles in plant growth, several strains of beneficial rhizobactria have been applied to improve plant nutrient absorption, biomass, and abiotic or biotic stress tolerance. In this study, we report the mechanisms of microbe-induced plant Fe assimilation, in which the plant growth promoting rhizobacteria (PGPR) Paenibacillus polymyxa BFKC01 stimulates plant's Fe acquisition machinery to enhance Fe uptake in Arabidopsis plants. Mechanistic studies show that BFKC01 transcriptionally activates the Fe-deficiency-induced transcription factor 1 ( FIT1), thereby up-regulating the expression of IRT1 and FRO2 . Furthermore, BFKC01 has been found to induce plant systemic responses with the increased transcription of MYB72 , and the biosynthetic pathways of phenolic compounds are also activated. Our data reveal that abundant phenolic compounds are detected in root exudation of the BFKC01-inoculated plants, which efficiently facilitate Fe mobility under alkaline conditions. In addition, BFKC01 can secret auxin and further improved root systems, which enhances the ability of plants to acquire Fe from soils. As a result, BFKC01-inoculated plants have more endogenous Fe and increased photosynthetic capacity under alkaline conditions as compared to control plants. Our results demonstrate the potential roles of BFKC01 in promoting Fe acquisition in plants and underline the intricate integration of microbial signaling in controlling plant Fe acquisition. [ABSTRACT FROM AUTHOR]

Incidence of iron (Fe) deficiency in human populations is an emerging global challenge. This study was conducted to evaluate the potential of iron sulphate combined with biochar and poultry manure for Fe biofortification of wheat grains in pH affected calcareous soil. In first two incubation studies, rates of sulfur (S) and Fe combined with various organic amendments for lowering pH and Fe availability in calcareous soil were optimized. In pot experiment, best rate of Fe along with biochar (BC) and poultry manure (PM) was evaluated for Fe biofortification of wheat in normal and S treated low pH calcareous soil. Fe applied with BC provided fair increase in root-shoot biomass and photosynthesis up to 79, 53 and 67%, respectively in S treated low pH soil than control. Grain Fe and ferritin concentration was increased up to 1.4 and 1.2 fold, respectively while phytate and polyphenol was decreased 35 and 44%, respectively than control in treatment where Fe was applied with BC and S. In conclusion, combined use of Fe and BC could be an effective approach to improve growth and grain Fe biofortification of wheat in pH affected calcareous soil. [ABSTRACT FROM AUTHOR]

Organisms have developed different strategies to cope with environmental conditions of low Fe availability based on the exudation of reducing, ligating, and acidifying compounds. In the context of Fe acquisition from soil, the effects of these reactive compounds have generally been considered independent and additive. However, highly efficient Fe acquisition strategies may rely on synergistic effects between reactive exudates. In the present study, we demonstrate that synergistic effects between biogenic ligands and a reductant (ascorbate) can occur in Fe mobilization from soil. Synergistic Fe mobilization was found for all ligands examined (desferrioxamine B (DFOB), 2'-deoxymugineic acid (DMA), esculetin, and citrate). The size and duration of the synergistic effect on Fe mobilization varied with ligand: larger effects were observed for the sideorphores compared to esculetin and citrate. For DFOB, the synergistic effect lasted for the 168 h duration of the experiment; for DMA, an initial synergistic effect turned into an antagonistic effect after 4 h because of enhanced mobilization of competing metals; and for esculetin and citrate, the synergistic effect was temporary (less than 24 h). Our results demonstrate that synergistic effects greatly enhance the reactivity of mixtures of compounds known to be exuded in response to Fe limitation. These synergistic effects could be decisive for the survival of plants and microorganisms under conditions of low Fe availability. [ABSTRACT FROM AUTHOR]

We combined lab experiments, a 2-year pot experiment, light microscopy and X-ray photoelectron spectroscopic measurements to understand the fate of Fe in biochar-amended soils with, and without, three sustainable Fe-fertilization strategies (siderite, aqueous extract of Amaranthus retroflexus either alone or enriched with FeSO 4 ). In addition, we examined biochar effects on plant-available micronutrients using metal Fe. We also assessed nonlinear interactions between biochar and Fe management strategies, evaluating the effectiveness of sustainable fertilization strategies in improving Fe-nutrition of kiwifruit vines under Fe-stressed conditions. Fe chlorosis symptoms of pot-cropped kiwifruit vines were pronounced in the biochar-amended soils, especially during the first season. However, the biochar rate adopted in this study was relatively high (5 g kg − 1 w/w) while the real impact of this strategy may change at lower rates. In the lab, increasing biochar rates progressively removed dissolved micronutrients from solution. Light microscopy revealed rust-colored patches on the biochar surface exposed to a Fe source in solution and XPS analyses confirmed that the biochar surface had become coated with Fe and O in ratios consistent with the formation of Fe-(hydr)oxides. Although we investigated one specific biochar, our results suggest that some redox reactions can act to form a micronutrient sink on the biochar surface. This mechanism likely contributed to binding soil Fe (through reactive functional groups on its surface) into plant-unavailable forms, promoting the occurrence of Fe chlorosis symptoms of kiwifruit vines grown in soils amended with biochar. We also confirmed the effectiveness of siderite and A. retroflexus extract enriched with FeSO 4 in alleviating the occurrence of Fe-deficiency symptoms in kiwifruit vines. [ABSTRACT FROM AUTHOR]

Greenhouse experiment was conducted to assess the iron (Fe) and zinc (Zn) fractionation patterns in soils of arbuscular mycorrhizal (AM) fungus-inoculated and uninoculated maize plants fertilized with varying levels of Fe and Zn. Soil samples were collected for Fe and Zn fractions and available Fe, Zn and phosphorus (P) contents besides organic and biomass carbon (BMC), soil enzymes and glomalin. Major portion of Fe and Zn fractionations was found to occur in the residual form. Mycorrhizal symbiosis increased the organically bound forms of Fe and Zn while reducing the crystalline oxide, residual Fe and Zn fractions, indicating the transformation of unavailable forms into available forms. Soil enzymes, viz. dehydrogenase and acid phosphatase activities in M+ soils, were significantly higher than M− soil consistently. Overall, the data suggest that mycorrhizal symbiosis enhanced the availability of Fe and Zn as a result of preferential fractionation and biochemical changes that may alleviate micronutrient deficiencies in calcareous soil. Abbreviations: AM: arbuscular mycorrhiza; Fe: Iron; Zn: Zinc; P: Phosphorous; Amox-Zn: amorphous oxide bound zinc; Cryox-Zn: crystalline oxide bound zinc; DAS: days after sowing; DTPA: diethylene Triamine Penta Acetic Acid; MnO2-Zn: manganese oxide bound zinc; OC-Zn: organically bound zinc; WSEX: water soluble plus exchangeable zinc; MnO2Fe: manganese oxide bound iron; OC-Fe: Organically bound iron; WSEX Fe: water soluble plus exchangeable iron. [ABSTRACT FROM AUTHOR]

Iron (Fe) bioavailability is the major issue of highly calcareous soils. Iron fertilization in calcareous soils is not much effective due to their rapid conversion into unavailable form. A field experiment was conducted to evaluate the effect of Fe fertilizer along with organic amendments for improving growth, yield and Fe biofortification of rice by manipulating pH of calcareous soil. Before transplanting rice seedlings, soil pH was lowered down up to 0.5-0.6 units by using 0.25% (w/w) elemental sulfur (S). For biofortification, Fe fertilizer (FeSO4.7H2O) at the rate of 15 kg ha-1 was applied with biochar (BC) and poultry manure (PM) in S treated calcareous soils. Results indicated that the combined application of Fe along with BC and PM enhanced plant growth, physiology and paddy yield and improved nutritional value of grain in pH manipulated calcareous soil. Applied treatments in S treated low pH soil resulted in increased Fe mobilization and translocation from root to grain. Grain Fe concentration raised up to 2 fold and 1.8 fold in treatments where Fe was applied with BC and PM in pH manipulated soil, respectively. Ferritin concentration significantly increased up to 3 fold and 2.73 fold by using Fe with BC and PM, respectively, in pH manipulated soil. Iron applied in combination with BC decreased phytate and polyphenols contents up to 18 and 47%, respectively, in S treated soil. The results may imply that the combined use of Fe with BC increased Fe biofortification (ferritin) of rice in pH manipulated calcareous soil. This increased level of ferritin in rice grains might be helpful to eliminate Fe deficiency in humans. [ABSTRACT FROM AUTHOR]

The deficiency of zinc (Zn) and iron (Fe) is a global issue causing not only considerable yield losses of food crops but also serious health problems. We have analysed Zn and Fe concentrations in the grains of two bread wheat cultivars along native gradient of micronutrient availability throughout Serbia. Although only 13% of the soil samples were Zn deficient and none was Fe deficient, the levels of these micronutrients in grain were rather low (median values of 21 mg kg − 1 for Zn and 36 mg kg − 1 for Fe), and even less adequate in white flour. Moreover, excessive P fertilization of calcareous soils in the major wheat growing areas strongly correlated with lower grain concentration of Zn. Our results imply that a latent Zn deficiency in wheat grain poses a high risk for grain quality relevant to human health in Serbia, where wheat bread is a staple food. [ABSTRACT FROM AUTHOR]

Iron (Fe) deficiency is one of the major yield-limiting factors in peanut (Arachis hypogaea L.), especially when grown in calcareous soils. The soils of the Pothwar region in Pakistan are calcareous in nature, exposing peanut to Fe deficiency. The molecular mechanisms governing Fe deficiency response in peanut have not been fully revealed. We compared 4 locally important varieties of peanut to evaluate Fe deficiency responses at the molecular level. The expression profiles of 7 important genes including AhIRT1, AhFRO1, AhNRAMP1, AhYSL1, AhYSL3.1, AhYSL4, and AhYSL6 in roots and young and old leaves of local peanut varieties were investigated 19 days after Fe deficiency treatment. Significant differences were observed for gene expression patterns among these varieties. The expression of AhIRT1 was upregulated only in Banki and BARD-699. However, some of the genes, like AhFRO1, AhNRAMP1, and other genes of the YSL family, were upregulated in BARI 2000 roots and young and old leaves, which has been reported for uptake and transport of Fe. BARI 2000 and Chakori had more accumulation of Fe in young leaves and roots in Fe deficiency conditions as compared to other varieties. This suggests that other mechanisms of Fe uptake and transport may be more important than AhIRT1 to mitigate Fe deficiency in BARI 2000 and Chakori. [ABSTRACT FROM AUTHOR]

Five cores from an Upper Jurassic carbonate mudstone succession deposited within a Middle East intra-shelf sub-basin were investigated to evaluate the vertical and lateral distribution of calcareous nannofossils. Coupled with lithologic elemental compositions, the results were interpreted in terms of paleoenvironmental and stratigraphic analysis. Six calcareous nannofossil species were identified from approximately 100 samples. Most of the species identified are dissolution-resistant taxa that belong to two clusters: oligotrophic and eutrophic surface waters. Poorly preserved foraminiferal remains were also found within the studied interval. Most of the identified foraminiferal genera are typical of a shallow marine environment, implying that they had been transported into the basin. Elemental analysis results from non-destructive micro-XRF analyses indicate a high percentage of calcium (Ca), moderate percentages of terrigenous-associated elements including silicon (Si), aluminum (Al), titanium (Ti), potassium (K), iron (Fe), and fluctuations in redox-sensitive trace elements (Mo, Ni, Cu, V) across the basin (proximal versus distal). Six geochemical clusters were identified using principal component analysis (PCA) and hierarchical clustering of principal components (HCPC) based on representative major and trace elements as input variables. Strong positive correlation was observed between terrigenous-associated elements and calcareous nannofossil relative abundance (RA), suggesting an increase in nutrient supply coupled with an increase in terrigenous-sourced materials and better oxygenation condition. Conversely, strong negative correlation was observed between calcareous nannofossil RA and redox-sensitive trace elements. In low-oxygen settings, environmental conditions were not favorable for the organisms to live, as shown by the decrease and absence of calcareous nannofossils and foraminiferal faunas. Variations in calcareous nannofossils and elemental compositions were likely controlled by sea-level fluctuations and other factors that resulted in stratification of the water column. • Variations in nannofossils and elemental compositions controlled by several factors including sea-level fluctuations. • The nannofossil species revealed lowproductivity oligotrophic surface waters and high-productivity eutrophic surface waters. • PCA and clustering of calcareous nannofossils, major and trace elements identified distinct clusters. • Strong positive correlation between terrigenous-associated elements and the relative abundance of nannofossils. [ABSTRACT FROM AUTHOR]

The short-term effectiveness of soil-applied humic acid–like substances [naturally complexed or uncomplexed with iron (Fe)] extracted from composted poultry (HLSP) and sheep (HLSS) manures in preventing lime-induced Fe chlorosis in Eureka lemon (Citrus lemonL.) cuttings grafted on sour orange (Citrus aurantiumL.) was investigated and compared with the commonly applied ethylenediamine di-2-hydroxyphenyl acetate ferric (FeEDDHA). Treatments were untreated plants and plants fertilized with FeEDDHA, HLSP, and HLSS injected into the soil at a total rate of 25 mg Fe per plant each. Chlorophyll concentration index (CCI) of the youngest fully expanded leaves, growth vigor, and leaf Fe concentration were measured. HLSP and HLSS, similar to FeEDDHA, resulted in significantly greater CCI values, growth vigor, and leaf Fe concentration compared to untreated plants. HLSP and HLSS offer potential alternative to FeEDDHA to prevent lime-induced Fe deficiency in Eureka lemon. Concentrates of HLSP and HLSS can be commercially prepared to offer an inexpensive and environmentally safe product. [ABSTRACT FROM AUTHOR]

Iron (Fe) deficiency is common in calcareous soils of southern Iran. Chemical forms of Fe in a calcareous soil were studied in the beneath and the interspace soils of five common range plant species. Results showed that electrical conductivity (EC) and organic matter (OM) content was significantly higher in the soil beneath canopies as compared to interspace soil. The reverse was true for pH of the soil except in case ofSalvia compressa. Among different forms of Fe, soluble and exchangeable Fe (SolEx-Fe) form was higher in the soil beneath canopy of all plant species as compared to interspaces. Similar results were recorded for Fe bound to organic materials (Om-Fe) but only in the case ofConvolvulus argyracanthus, Echinops glanduloso-punctatus, andCentaurea intricata. In the soil beneathConvolvulus argyracanthusandCentaurea intricatacanopies Fe bound to manganese (Mn) oxides (Mnox-Fe) was significantly higher but the amount of residual Fe (Res-Fe) was lower compared to the interspace soil. A reverse trend was, however, observed in the case ofTeucrium polium, demonstrating differential distribution of Fe forms at the two locations. The summation of reactive Fe forms [SolEx-Fe, Fe bound to carbonates (Car-Fe), and Om-Fe] known as readily or potentially available Fe was higher in the soil under canopies than in interspace soils. It is assumed that the higher contents of OM and lower values of pH enhanced Fe availability in the soil under plant canopies in comparison with interspace soil. [ABSTRACT FROM AUTHOR]

Iron is an essential element for all organisms which plays a crucial role in important biochemical processes such as respiration and photosynthesis. Iron deficiency seems to be an important problem in many calcareous soils. Biological dissimilatory Fe(III) reduction increases iron availability through reduction of Fe(III) to Fe(II). The aim of this study was to isolate, identify and evaluate some bacterial isolates for their abilities to reduce Fe(III) in two calcareous soils. Three bacterial isolates were selected and identified from paddy soils by using 16S rRNA amplification and then inoculated to sterilized and non-sterilized calcareous soils in the presence and absence of glucose. The results showed that all isolates belonged to Bacillus genus and were capable of reducing Fe(III) to Fe(II) in vitro condition. The amount of Fe(III) reduction in sterilized calcareous soils was significantly higher when inoculated with PS23 isolate and Shewanella putrefaciens ( S. putrefaciens) (as positive control) compared to PS16 and PS11 isolates. No significant difference was observed between PS11 and PS16 isolates in the presence of indigenous microbial community. The results also revealed that glucose had a significant effect on Fe(III) reduction in the examined calcareous soil samples. The amount of Fe(III) reduction increased two-fold when soil samples were treated with glucose and inoculated by S. putrefaciens and PS23 in non-sterilized soils. [ABSTRACT FROM AUTHOR]

Iron availability in alkaline and calcareous soils is limited because of high pH and calcium carbonate contents. Various sources may have different solubilities within soil and may result in varying degrees of Fe availability. An incubation study was conducted to evaluate effectiveness of different sources of Fe to maintain water soluble Fe in different soils over passage of time. For this purpose, three different soils were incubated with various organic (Fe-EDDHA, Fe-DTPA, FYM) and inorganic (ferrous sulphate, vivianite) Fe sources for the period of four weeks. All amendments were adjusted to maintain 20 mg kg-1 of soil Fe except FYM. Iron sources showed significantly different behavior in maintaining soil Fe in different soils. The chelates of Fe proved very effective in maintaining soil solution Fe throughout the incubation period. Fe-EDDHA maintained 12 mg kg-1 with 56% recovery of total Fe added Followed by Fe-DTPA (with 30% recovery). Recovery of ferrous suphate was negligible on the first day of incubation. Vivianite which was prepared by mixing DAP fertilizer with FeSO4.7H2O also rapidly converted in to insoluble fractions on first contact to soils but maintained slightly more amount of soluble Fe as compared ferrous sulphate. [ABSTRACT FROM AUTHOR]

Previous pot cropping and laboratory incubation experiments were consistent with field observations showing that temporary flooding before cropping can increase the availability of soil Fe to plants. To study the effect of temporary flooding on changes in soil Fe phytoavailability we used 24 highly calcareous, Fe chlorosis-inducing soils to carry out a pot experiment where peanut and chickpea were successively grown after flooding for 30 d. At the end of the cropping experiment, the preflooded soil samples exhibited higher concentrations of acid oxalate-, citrate/ascorbate- and diethylenetriaminepentacetic acid (DTPA)-extractable Fe (Feox, Feca, and FeDTPA, respectively) than the control (nonflooded) samples. Also, Feox and Feca exhibited no change by effect of reflooding of the cropped soils or three wetting-drying cycles in freeze-dried slurries of soils previously incubated anaerobically for several weeks. Leaf chlorophyll concentration (LCC) in both peanut and chickpea was greatly increased by preflooding. The best predictor for LCC was Feox, followed by Feca and FeDTPA. The LCC-soil Fe relationships found suggest that the Fe species extracted by oxalate and citrate/ascorbate from preflooded soils were more phytoavailable than those extracted from control soils. However, the increased phytoavailability of extractable Fe forms was seemingly limited to the first crop (peanut). Flooding dramatically increased FeDTPA; however, high FeDTPA levels did not result in high LCC values, particularly in the second crop. Therefore, this test is a poor predictor of the severity of Fe chlorosis in preflooded soils. [ABSTRACT FROM AUTHOR]

A factorial design with different levels of elemental S and cow manure was used to investigate the effects of S and manure on SO4-S, P and micronutrient availability in a calcareous saline–sodic soil. The results revealed that the recovery of SO4-S increased significantly (p≤0.05) in all treatments as elemental S increased, particularly when in combination with manure. The interactional effects of S° and manure application rates resulted in a decrease in soil pH of 0.1 to 0.9 units and increases in soil EC from 0.1 to 2.6 dS m−1as result of an increase in the number of oxidisers and the oxidation rate of elemental S. Application of S° in combination with manure led to an increase in soil-available-P (0.6–40 mg kg−1), DTPA-Zn (0.2–3.9 mg kg−1) and DTPA-Fe (0.1–5.6 mg kg−1). [ABSTRACT FROM AUTHOR]

This study was conducted to understand the mechanisms governing P-sorption and desorption by calcareous soils (up to 48% CaCO3). Batch experiments with KCl as background were carried out by adding varying amount of P up to 100 mgP.L−1. The desorption percentage (%DES) results show that little P was released from the adsorbed phase. Principal component analysis was applied to evaluate the combined influence of soil components on P sorption. The complex P sorption process can be related to specific soil components by the following equation: P−sorption=−2.20 (CaCO3% )−0.04 (Fe−oxide)+0.04 (pHe)+11.02 (sand % )+3.35 (silt)−10.73 (clay)−1.24 (EC)−0.22 (OM)−0.81 (CEC)−1.93 (P−Olsen) (R2=0.9941, SSE=380). Sand% and clay% are the most significant variables for modelling P sorption data. The derived equation could be applied to predict P sorption in other soils that have similar compositions to those investigated herein. The degree of P saturation (DPS) threshold level for all soils was less than 3% except in the soil with the lowest iron oxide. All of the studied soils have exceeded the environmentally unacceptable P concentration except the soil with the lowest iron oxide content. [ABSTRACT FROM AUTHOR]