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Iron plays a major role in photosynthesis. That’s why a shortage directly affects the production capacity of the plant. The application of chelates has made iron much more easy to absorb. Nevertheless it’s an element that we have to keep an eye on.

IJzer is onder normale wortelcondities vaak moeilijk opneembaar voor planten. Dat geldt ook en misschien wel juist voor substraatteelten. IJzerchelaten – organische moleculen die ijzerionen adsorberen en afstaan aan of in plantenwortels – bieden uitkomst. Bij de keuze van het juiste chelaat dient men niet alleen oog te hebben voor de pH van de voedingsoplossing of in de mat. Zij kunnen ook verbindingen aangaan met andere spoorelementen, waardoor drainwateranalyse soms een vertekend beeld geeft van wat er werkelijk beschikbaar is.

IJzer is een onmisbaar voedingselement, dat nodig is voor de vorming van bladgroen en zo chlorose voorkomt. Omdat het element normaal niet opgelost blijft – en dan niet beschikbaar is voor de plant – zijn al jaren ijzerchelaten voorhanden. Bij een nieuwe meststof is het ijzer op een andere manier gebonden, namelijk met een combinatie van polyfosfaten. Bij toediening via een aparte bak blijkt het in de praktijk goed te werken. De meststof heeft daarnaast andere effecten, zoals minder bladrand en makkelijker UV-ontsmetting. Recent onderzoek en praktijkervaringen geven vergelijkbare resultaten.

Iron plays a major role in photosynthesis. That’s why a shortage directly affects the production capacity of the plant. The application of chelates has made iron much more easy to absorb. Nevertheless it’s an element that we have to keep an eye on.

IJzer is onder normale wortelcondities vaak moeilijk opneembaar voor planten. Dat geldt ook en misschien wel juist voor substraatteelten. IJzerchelaten – organische moleculen die ijzerionen adsorberen en afstaan aan of in plantenwortels – bieden uitkomst. Bij de keuze van het juiste chelaat dient men niet alleen oog te hebben voor de pH van de voedingsoplossing of in de mat. Zij kunnen ook verbindingen aangaan met andere spoorelementen, waardoor drainwateranalyse soms een vertekend beeld geeft van wat er werkelijk beschikbaar is.

Iron deficiency chlorosis is a nutritional disorder in plants which reduces crop yields both quantitatively and qualitatively, and causes large economic losses. It occurs world-wide, predominantly in plants grown on calcareous soils, as a result of a limited bioavailability of iron related to the poor solubility of iron at high soil-pH (7.5-8.5). Iron fertilizers based on FeEDDHA (iron ethylene diamine-N,N'-bis(hydroxy phenyl acetic acid)) chelates are among the most efficient in preventing and remedying iron deficiency in soil-grown plants. FeEDDHA based fertilizers comprise mixtures of FeEDDHA components which can be divided into racemic o,o-FeEDDHA, meso o,o-FeEDDHA, o,p-FeEDDHA and rest-FeEDDHA. Both the composition of FeEDDHA based fertilizers and the properties of the FeEDDHA components differ considerably. The fate and effectiveness of FeEDDHA chelates in soil-plant systems were examined in order to facilitate a more efficient use of FeEDDHA fertilizer. Upon interaction with soils, racemic and meso o,o-FeEDDHA largely remained in solution, whereas o,p-FeEDDHA and rest-FeEDDHA were largely removed. In plant experiments it was found that, on soils in which plants from the blank treatment became chlorotic, the iron concentration in soil solution, governed by racemic and meso o,o-FeEDDHA, determined iron uptake by plants. When introduced into soil-plant systems, the concentration of racemic and meso o,o-FeEDDHA underwent an initial concentration drop due to adsorption, and gradually declined further. In particular for meso o,o-FeEDDHA, this gradual decline was not related to iron uptake by plants. The gradual decline could not be explained by biodegradation, which did not significantly affect the concentration of FeEDDHA components. From mechanistic multi surface modeling and batch interaction experiments it was concluded that there is a basis for assuming that under soil conditions iron can be displaced from o,o-FeEDDHA components by copper. This displacement reaction was closer examined in goethite suspensions, and it was found to predominantly take place on reactive surfaces rather than in solution. Factors enhancing adsorption also enhanced the rate of the displacement reactions. The observed concentration behaviour of meso o,o-FeEDDHA in soil-plant systems could be explained from the displacement reaction. Furthermore, the effectiveness of EDDHA ligands in chelating and mobilizing iron from soil, after delivering iron at the plant root (the so-called “shuttle mechanism”) was examined. Plant experiments provided experimental support for a re-chelation mechanism, but results from batch interaction experiments indicated that the efficiency in chelating iron from soil is probably low as a result of complexation of other cations, in particular copper. In conclusion a conceptual model for the behaviour of FeEDDHA components in soil-plant systems was composed. The essence of the model consists of three processes: 1) FeEDDHA adsorption, 2) iron displacement from FeEDDHA by copper on a soil reactive surface followed by release of CuEDDHA into soil solution, and 3) re-adsorption of CuEDDHA. Clay content, iron(hydr)oxide content and copper content were identified as soil characteristics substantially compromising the effectiveness of FeEDDHA components.

Iron deficiency chlorosis is a nutritional disorder in plants which reduces crop yields both quantitatively and qualitatively, and causes large economic losses. It occurs world-wide, predominantly in plants grown on calcareous soils, as a result of a limited bioavailability of iron related to the poor solubility of iron at high soil-pH (7.5-8.5). Iron fertilizers based on FeEDDHA (iron ethylene diamine-N,N'-bis(hydroxy phenyl acetic acid)) chelates are among the most efficient in preventing and remedying iron deficiency in soil-grown plants. FeEDDHA based fertilizers comprise mixtures of FeEDDHA components which can be divided into racemic o,o-FeEDDHA, meso o,o-FeEDDHA, o,p-FeEDDHA and rest-FeEDDHA. Both the composition of FeEDDHA based fertilizers and the properties of the FeEDDHA components differ considerably. The fate and effectiveness of FeEDDHA chelates in soil-plant systems were examined in order to facilitate a more efficient use of FeEDDHA fertilizer. Upon interaction with soils, racemic and meso o,o-FeEDDHA largely remained in solution, whereas o,p-FeEDDHA and rest-FeEDDHA were largely removed. In plant experiments it was found that, on soils in which plants from the blank treatment became chlorotic, the iron concentration in soil solution, governed by racemic and meso o,o-FeEDDHA, determined iron uptake by plants. When introduced into soil-plant systems, the concentration of racemic and meso o,o-FeEDDHA underwent an initial concentration drop due to adsorption, and gradually declined further. In particular for meso o,o-FeEDDHA, this gradual decline was not related to iron uptake by plants. The gradual decline could not be explained by biodegradation, which did not significantly affect the concentration of FeEDDHA components. From mechanistic multi surface modeling and batch interaction experiments it was concluded that there is a basis for assuming that under soil conditions iron can be displaced from o,o-FeEDDHA components by copper. This displacement reaction was closer examined in goethite suspensions, and it was found to predominantly take place on reactive surfaces rather than in solution. Factors enhancing adsorption also enhanced the rate of the displacement reactions. The observed concentration behaviour of meso o,o-FeEDDHA in soil-plant systems could be explained from the displacement reaction. Furthermore, the effectiveness of EDDHA ligands in chelating and mobilizing iron from soil, after delivering iron at the plant root (the so-called “shuttle mechanism”) was examined. Plant experiments provided experimental support for a re-chelation mechanism, but results from batch interaction experiments indicated that the efficiency in chelating iron from soil is probably low as a result of complexation of other cations, in particular copper. In conclusion a conceptual model for the behaviour of FeEDDHA components in soil-plant systems was composed. The essence of the model consists of three processes: 1) FeEDDHA adsorption, 2) iron displacement from FeEDDHA by copper on a soil reactive surface followed by release of CuEDDHA into soil solution, and 3) re-adsorption of CuEDDHA. Clay content, iron(hydr)oxide content and copper content were identified as soil characteristics substantially compromising the effectiveness of FeEDDHA components.

Van alle gebreksziekten komt ijzergebrek het vaakst voor in de glastuinbouw. Bij een gebrek worden de jonge bladeren geel tussen de nerven. Dat komt omdat er te weinig chlorofyl gevormd wordt. IJzergebrek tast daarom direct het productievermogen van de plant aan. Ook tal van andere processen zijn ijzerafhankelijk. Veel tuinbouwgewassen - zoals roos - zijn gevoelig voor ijzergebrek. Door chelaten is de toediening niet meer zo lastig als vroeger. Maar er blijft een constante aandacht voor pH, concentratie van andere elementen en goede groeiomstandigheden nodig. Ook zonder gele bladeren kan er al productieverlies optreden

Van alle gebreksziekten komt ijzergebrek het vaakst voor in de glastuinbouw. Bij een gebrek worden de jonge bladeren geel tussen de nerven. Dat komt omdat er te weinig chlorofyl gevormd wordt. IJzergebrek tast daarom direct het productievermogen van de plant aan. Ook tal van andere processen zijn ijzerafhankelijk. Veel tuinbouwgewassen - zoals roos - zijn gevoelig voor ijzergebrek. Door chelaten is de toediening niet meer zo lastig als vroeger. Maar er blijft een constante aandacht voor pH, concentratie van andere elementen en goede groeiomstandigheden nodig. Ook zonder gele bladeren kan er al productieverlies optreden

Several iron chelate based methods for removing hydrogen sulphide from gas streams have been developed over the years. Notwithstanding the number of hydrodesulphurisation plants already in operation, the development of these processes has been more a kind of an art rather than a result of rational process design. Data concerning the reactivity of ferrous chelates with oxygen and of femc chelates with hydrogen sulphide obtained under industrial conditions, are practically absent. The same holds for the diffusivities of iron chelates. However, these data form the basis for a rational design of both iron regenerators and H2S absorbers. Certain types of structured packings may prove to be superior in these applications, but have not been tested yet. The role of the sulphur produced by the absorption of hydrogen sulphide, is complex. It often causes fouling of the absorber, thus usually reducing absorption efficiency. On the other hand, sulphur also interferes with the absorption of H2S because it tends to stick to the gasliquid interface. The latter may result in higher column efficiencies.

Several iron chelate based methods for removing hydrogen sulphide from gas streams have been developed over the years. Notwithstanding the number of hydrodesulphurisation plants already in operation, the development of these processes has been more a kind of an art rather than a result of rational process design. Data concerning the reactivity of ferrous chelates with oxygen and of femc chelates with hydrogen sulphide obtained under industrial conditions, are practically absent. The same holds for the diffusivities of iron chelates. However, these data form the basis for a rational design of both iron regenerators and H2S absorbers. Certain types of structured packings may prove to be superior in these applications, but have not been tested yet. The role of the sulphur produced by the absorption of hydrogen sulphide, is complex. It often causes fouling of the absorber, thus usually reducing absorption efficiency. On the other hand, sulphur also interferes with the absorption of H2S because it tends to stick to the gasliquid interface. The latter may result in higher column efficiencies.

Several iron chelate based methods for removing hydrogen sulphide from gas streams have been developed over the years. Notwithstanding the number of hydrodesulphurisation plants already in operation, the development of these processes has been more a kind of an art rather than a result of rational process design. Data concerning the reactivity of ferrous chelates with oxygen and of femc chelates with hydrogen sulphide obtained under industrial conditions, are practically absent. The same holds for the diffusivities of iron chelates. However, these data form the basis for a rational design of both iron regenerators and H2S absorbers. Certain types of structured packings may prove to be superior in these applications, but have not been tested yet. The role of the sulphur produced by the absorption of hydrogen sulphide, is complex. It often causes fouling of the absorber, thus usually reducing absorption efficiency. On the other hand, sulphur also interferes with the absorption of H2S because it tends to stick to the gasliquid interface. The latter may result in higher column efficiencies.

Het optreden van verschijnselen van ijzergebrek en mangaangebrek bij populieren en wilgen, gebaseerd op waarnemingen gedurende de laatste dertig jaar wordt besproken. De gegevens over ijzer- en mangaangehalten van het blad zijn in tabelvorm weergegeven