Effect of Iron Chelates and their Application Methods on Iron Nutrition Status of Bean Plant (Phaseolus vulgaris) in a Calcareous Soil

Identification and synthesis of new organic iron chelates with higher efficiency than conventional synthetic chelates seems to be necessary to improve the nutritional status of iron in calcareous soils of Iran. In this study, first the amino acid chelates of tyrosine-iron (Fe-Tyr) acid-hydrolyzed chitosan-iron (Fe-Chi) were synthesized by laboratory methods and then some of their properties were characterized. A greenhouse experiment was designed as a factorial experiment based on completely randomized design with three replications including three types of iron chelate, Fe-Chi, Fe-Tyr and Fe-EDDHA (control) and three methods of soil application, fertigation and foliar application. Bean plants were grown and some growth parameters and total iron content in shoot and root were determined. The activity of root and leaf FCR (Ferric Chelate Reductase) enzymes were measured. The results of experimental and theoretical data showed that the tyrosine and chitosan were complexed with iron metal. The results showed that the highest shoot dry weight was observed in soil application of Fe-Chi and fertigation of Fe-Tyr. Also, fertigation of Fe-Chi increased root dry weight compared to control significantly. The highest content of total iron (10.3 mg pot-1) was observed in soil application of Fe-Chi in bean shoots which showed 36% higher Fe uptake than Fe-EDDHA. There was a significant positive correlation between shoot dry weight with iron and nitrogen content in shoots of bean plants. Investigation of root FCR enzyme activity revealed that soil application of Fe-Chi and fertigation of Fe-Tyr had the highest mean of FCR activity. In the foliar and fertigation application of Fe-Tyr, leaf FCR activity increased to 40 days after the start of the experiment. Soil application of Fe-Chi and foliar of Fe-Tyr during plant growth can improve the nutritional status of iron in bean plant