Sandra López-Rayo

Evaluation of Fe-N,N′-Bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetate (HBED/Fe3+) as Fe carrier for soybean (Glycine max) plants grown in calcareous soil

AimsThe efficacy of N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid (HBED) as an Fe source in plant nutrition for soybean (Glycine max) plants grown in calcareous soil under controlled conditions was studied.MethodsThe ability of ethylenediamine-N,N′-bis(o-hydroxyphenylacetic) acid (o,oEDDHA/57Fe3+) and HBED/57Fe3+ at increasing concentrations and the long lasting effect were evaluated. In addition, iron nutrition was studied considering the Fe uptake from the chelates prepared with the isotope 57Fe. Further, the SPAD index, total Fe and 57Fe content in plant were analyzed and soluble and available 57Fe fractions in soil were determined over time.ResultsDoses experiment indicated that a higher concentration of HBED/57Fe3+ as compared to o,oEDDHA/57Fe3+ is necessary for obtaining the same 57Fe absorption by the plant; however, these differences were found to be lower in the second sampling time as compared to the first one. This long lasting effect of HBED/Fe3+ was corroborated in the long term experiment. Moreover, it was found that the load of Fe in the pods was higher when using HBED/57Fe3+ than when o,oEDDHA/57Fe3+ was used. The soil extract analysis for each sampling time indicated that HBED/57Fe3+ presented a higher stability in soil than o,oEDDHA/57Fe3+ over time.ConclusionThe HBED/Fe3+ could be a long lasting alternative to EDDHA/Fe3+ for correcting the iron chlorosis of dicotyledonous plants grown on calcareous soils.

Novel chelating agents as manganese and zinc fertilisers: characterisation, theoretical speciation and stability in solution

Abstract Mineral, complex and chelated micronutrient fertilisers are widely used in agriculture. However, there have been few studies on manganese and zinc fertilisers. In fact, specific chelating agents to provide these micronutrients to plants have not been found, in contrast to iron. This work considers the interactions of novel and traditional ligands in micronutrient mixtures used in hydroponics and fertigation. Theoretical speciation studies comparing the stability in solution have been carried out to simulate the possible interactions that can affect Fe, Mn and Zn in aqueous formulations containing these micronutrients. Unknown stability constants of ligands with Zn and Mn have been determined. Also, theoretical speciation investigations in hydroponic conditions have been carried out. It has been found that the new chelating agents, IDHA and EDDS, and the poorly studied o,p-EDDHA, can be good alternatives to the traditional sources such as EDTA, HEEDTA and DTPA principally for Zn fertilisers. The Mn and Zn chelates with o,p-EDDHA and complexes with lignosulfonate and gluconate have also shown high stability in a hydroponic nutrient solution, maintaining more than 80% Mn in solution until pH 10. The presence of o,o-EDDHA/Fe3+ and o,p-EDDHA/Fe3+ enhances the stability of Zn in solution in the mixed fertilisers. More studies with substrates are necessary to confirm these results and to extend them to other agronomic conditions.

Blood Meal-Based Compound. Good Choice as Iron Fertilizer for Organic Farming

Prevention of iron chlorosis with Fe synthetic chelates is a widespread agronomical practice but implies high costs and environmental risks. Blood meal is one of the main fertilizers allowed to be used in organic farming. Through this work a novel blood meal fertilizer was audited. Measurements such as FTIR, Raman, electron paramagnetic resonance, and Mössbauer spectroscopy, UV-visible properties, stability against pH, and batch experiments were performed to characterize and assess the reactivity on soil constituents and agronomic soils. The spectroscopy findings give clear indications that Fe is in the ferric oxidation state, is hexacoordinated, and has a low-spin form suggesting a similar structure to hemin and hematin. A spectrophotometric method at 400 nm was validated to quantify blood meal concentration at low electrolyte concentrations. Batch experiments demonstrated high reactivity of blood meal fertilizer with soil constituents, mainly in the presence of calcium, where aggregation processes are predominant, and its ability to take Fe from synthetic Fe (hydr)oxides. The beneficial profile of blood meal by a providing nitrogen source together with the capability to keep the Fe bound to porphyrin organic compounds makes it a good candidate to be used as Fe fertilizer in organic farming.

Reactivity and effectiveness of traditional and novel ligands for multi-micronutrient fertilization in a calcareous soil

This study compares the effectiveness of multi-micronutrient formulations containing iron (Fe), manganese (Mn), and zinc (Zn) with traditional (EDTA, DTPA, HEEDTA, and EDDHAm) or novel chelates (o,p-EDDHA, S,S-EDDS, and IDHA) and natural complexing agents (gluconate and lignosulfonate). The stability and reactivity of the formulations were studied on batch experiments with calcareous soil and by speciation modeling. Formulations containing traditional ligands maintained higher Mn but lower Zn concentration in soil solution than the novel ligands. The gluconate and lignosulfonate maintained low concentrations of both Mn and Zn in soil solution. Selected formulations were applied into calcareous soil and their efficacy was evaluated in a pot experiment with soybean. The formulation containing DTPA led to the highest Zn concentration in plants, as well as the formulation containing S,S-EDDS in the short-term, which correlated with its biodegradability. The application of traditional or novel ligands in formulations did not result in sufficient plant Mn concentrations, which was related to the low Mn stability observed for all formulations under moderate oxidation conditions. The results highlight the need to consider the effect of metals and ligands interactions in multi-nutrient fertilization and the potential of S,S-EDDS to be used for Zn fertilization. Furthermore, it is necessary to explore new sources of Mn fertilization for calcareous soils that have greater stability and efficiency, or instead to use foliar fertilization.

Synthesis and chemical characterization of the novel agronomically relevant pentadentate chelate 2-(2-((2-hydroxybenzyl)amino)ethylamino)-2-(2-hydroxyphenyl)acetic acid (DCHA).

Iron chelates analogous to o,o-EDDHA/Fe(3+) are the fertilizers chosen to treat iron chlorosis in plants growing on calcareous soil. The isomer o,p-EDDHA/Fe(3+) presents less stability but faster assimilation by the plant than o,o-EDDHA/Fe(3+), because only five coordinating groups are able to complex Fe(3+). The new chelating agent 2-(2-((2-hydroxybenzyl)amino)ethylamino)-2-(2-hydroxyphenyl)acetic acid (DCHA) has been synthesized to obtain an iron fertilizer with intermediate stability between o,o-EDDHA/Fe(3+) and o,p-EDDHA/Fe(3+) and with fast assimilation. Its synthesis has been done starting from phenol, N-acetylethylendiamine, glyoxylic acid, and NaOH in a three-step sequence. The purity of the DCHA chelating agent, its protonation, and Ca(2+), Mg(2+), Fe(3+), and Cu(2+) stability constants, together with its ability to maintain iron in solution in different agronomic conditions, have been determined. The results indicate that the chelate DCHA/Fe(3+) has intermediate stability between those of o,o-EDDHA/Fe(3+) and o,p-EDDHA/Fe(3+) complexes and that it is capable of maintaining the Fe(3+) in agronomic conditions. This new chelating agent may be effective in correcting iron chlorosis in plants.

Timing for a sustainable fertilisation of Glycine max by using HBED/Fe3+ and EDDHA/Fe3+ chelates

BACKGROUND Efficient use of Fe chelates is crucial to avoid environmental risks and reduce economic losses. HBED/Fe3+ has been recently approved by the European Union for soil fertilisation, but studies delving into the best timing for its application are necessary. In this work, a batch incubation experiment and two biological experiments were developed to determine the optimal physiological stage for a sustainable application of HBED/Fe3+ in soil fertilisation compared with EDDHA/Fe3+ fertilisers using 57 Fe. RESULTS HBED/Fe3+ demonstrated a high durability in soils and soil materials, maintaining more than 80% of Fe chelated after 70 days, and its application at an early physiological stage resulted in a high Fe accumulation in soybean and soil after 36 days. In contrast, the stability of EDDHA/Fe3+ decreased because of the retention of its lowest stable isomers. The best timing for chelates application was confirmed in a 52 day experiment. The application of HBED/Fe3+ at the early stage increased the Fe translocation to fruits; while o,o-EDDHA/Fe3+ accumulated more Fe in fruits when added at the fructification stage. CONCLUSION The high HBED/Fe3+ stability in calcareous soil requires a differentiate application timing, and its addition at early physiological stages leads into the most efficient fertilisation.

Thermodynamic Database Update to Model Synthetic Chelating Agents in Soil Systems

Poliaminocarboxylate and polyaminophenolcarboxylate chelating agents, being the most representatives EDTA and o,o-EDDHA, have been profusely studied by our research team during the last 25 years because they are synthetized to be mainly used as micronutrient fertilizers to correct nutritional disorders affecting largely on crop yields placed under Mediterranean conditions. In the last years new chelating agents were designed and synthesized and the most of them were proposed to be included in the current European Directive on Fertilizers. Overall chelating agent properties, including equilibrium in soil by modeling, should be taken in account in order to check the iron chlorosis correction ability. Chemical speciation programs such as MINTEQA2, and most recently VMinteq, are being successfully used as tools to predict the behavior of each novel chelating agent in soil-plant system. Nowadays just one polyaminophenolcarboxylate chelating agent (o,o-EDDHA) is available into a VMinteq-compatible database (Lindsay’s database) whereas more than seven of these type of products are authorized by European fertilizers normative to be used as micronutrient fertilizers. Therefore the aim of this work was the database updating to include all chelating agents related to o,o-EDDHA and EDTA whose complete characterization is performed and published elsewhere. Once database is updated, further modelization studies such as equilibrium reactions and adsorption isotherms with solid phase may be readily performed to get fundamental information and understand the reactivity of these recalcitrant polyaminophenolcarboxylates in soils.

Efficacy of Micronutrient Chelate Treatments in Commercial Crop of Strawberry on Sand Culture

Strawberry production is usually carried out in Spain on sand substrate under fertigation. Micronutrient chelates are frequently applied as ethylenediaminetetraacetic acid (EDTA) chelates; EDTA is a recalcitrant chelating agent so the concern about the environmental fate of EDTA applied in agriculture has risen. In this work, the efficacy of iron, manganese, zinc, and copper in two alternative chelating agents has been evaluated: the biodegradable N-(1,2-dicarboxyethyl)-D,L-aspartic acid (IDHA) and a combination of the regioisomers ethylenediamine-N,N´-bis(2-hydroxyphenylacetic) acid (o,o-EDDHA) and ethylenediamine-N-(2-hydroxyphenylacetic)-N´-(4-hydroxyphenylacetic) acid (o,p-EDDHA) (called EDDHA mix). Doses were split according to the stability of the chelates in three or six weekly applications. Experiment started 2 January 2010. Leaf samples were taken 6, 12, and 17 weeks after the first application. Foliar analysis, in comparison with chlorophyll indices based on Soil Plant Analysis Development (SPAD) measurement, was used to evaluate chelate efficacy. No differences between treatments were found for the SPAD index, but the SPAD increment was greater for the IDHA treatment during the whole assay. However, foliar analysis was the most adequate method for evaluating differences among the three chelates. The treatment based on EDDHA mix and the IDHA chelates showed greater Fe content in leaves in the first and last periods respectively. The EDDHA mix and EDTA were better alternatives for Zn nutrition than IDHA. Manganese content in leaf was sufficient and not affected by the treatment used. Copper content in leaf showed similar results for all treatments. The Fe/Mn molar ratio showed results similar to those obtained for Fe contents in leaf. The IDHA and EDDHA mix treatments produced similar quality parameters in fruits as EDTA. As conclusion, IDHA and EDDHA mix could be good alternatives for recalcitrant EDTA to apply micronutrient chelates in strawberry plants in fertigation.

TIMING FOR A SUSTAINABLE FERTILIZATION WITH HBED/Fe3+ AND EDDHA/Fe3+ CHELATES OF Glycine max

BACKGROUND Efficient use of Fe chelates is crucial to avoid environmental risks and reduce economic losses. HBED/Fe3+ has been recently approved by the European Union for soil fertilisation, but studies delving into the best timing for its application are necessary. In this work, a batch incubation experiment and two biological experiments were developed to determine the optimal physiological stage for a sustainable application of HBED/Fe3+ in soil fertilisation compared with EDDHA/Fe3+ fertilisers using 57 Fe. RESULTS HBED/Fe3+ demonstrated a high durability in soils and soil materials, maintaining more than 80% of Fe chelated after 70 days, and its application at an early physiological stage resulted in a high Fe accumulation in soybean and soil after 36 days. In contrast, the stability of EDDHA/Fe3+ decreased because of the retention of its lowest stable isomers. The best timing for chelates application was confirmed in a 52 day experiment. The application of HBED/Fe3+ at the early stage increased the Fe translocation to fruits; while o,o-EDDHA/Fe3+ accumulated more Fe in fruits when added at the fructification stage. CONCLUSION The high HBED/Fe3+ stability in calcareous soil requires a differentiate application timing, and its addition at early physiological stages leads into the most efficient fertilisation.

Physiological responses in roots of the grapevine rootstock 140 Ruggeri subjected to Fe deficiency and Fe-heme nutrition.

Iron (Fe)-heme containing fertilizers can effectively prevent Fe deficiency. This paper aims to investigate root physiological responses after a short period of Fe-heme nutrition and Fe deficiency under two pH conditions (with or without HEPES) in the Fe chlorosis-tolerant grapevine rootstock 140 Ruggeri. Organic acids in root exudates, Fe reduction capacity, both roots and root exudates contributions, together with other physiological parameters associated to plant Fe status were evaluated in plants grown in hydroponics. Analyses of root tips by SEM, and Raman and IR spectra of the precipitates of Fe-heme fertilizers were performed. The physiological responses adopted by the tolerant 140 Ruggeri to the application of Fe-heme indicated an increased Fe reduction capacity of the roots. This is the first report showing oxalic, tartaric, malic and ascorbic as major organic acids in Vitis spp. root exudates. Plants reacted to Fe deficiency condition exuding a higher amount of ascorbic acid in the rhizosphere. The presence of HEPES in the medium favoured the malic acid exudation. The lowest concentration of oxalic acid was found in exudates of plants subjected to Fe-heme and could be associated to a higher accumulation in their root tips visualized by SEM analysis.