Alleviation of Fe-induced chlorosis of soybean plants grown in calcareous soil by a freeze-dried iron fertilizer containing siderophores produced by Rhizobium radiobacter

The concerns about the unsustainability of traditional synthetic Fe chelates lead to the search for new environmentally friendly alternatives, such as siderophores-based fertilizers. In this work, the focus was on the evaluation of a bio-based Fe-chelate fertilizer obtained from the culture of the siderophore-producer bacterium Rhizobium radiobacter . The suitability of a freeze-dried fertilizer formulated from a R. radiobacter culture labeled with 57 Fe to alleviate Fe chlorosis in soybean plants cultivated in calcareous soil was analyzed and the new potential Fe fertilizer was evaluated in comparison to the traditional synthetic chelate o,o EDDHA/ 57 Fe 3+ . This natural chelate was able to maintain chlorophyll content stable during all the pot trials and presented greater Fe concentration in the remaining soil fractions serving as an Fe pool for a long time whereas o,o EDDHA/ 57 Fe 3+ could supply Fe quickly. The new bio-based Fe siderophore fertilizer, derived from R. radiobacter culture, could be a green substitute to conventional synthetic chelates to address Fe chlorosis in calcareous soil conditions. • Traditional synthetic iron chelates have been used to treat iron chlorosis in crops. • A novel freeze-dried Fe fertilizer was prepared from R. radiobacter culture containing siderophores. • The new bio-based Fe fertilizer achieved similar leaf chlorophyll SPAD values to Fe synthetic fertilizer. • A second application of the Fe bio-based Fe fertilizer addressed Fe chlorosis in the medium term. • The fertilization with the Fe freeze-dried fertilizer improves the Fe availability in calcareous soil.