An innovative green iron-fertilizer, produced biotechnologically, for correcting iron chlorosis of soybean plants grown in calcareous soils

Iron deficiency is one of the main causes of chlorosis in plants, which leads to the loss in the field crops quality and yield. Iron-deficiency is a worldwide problem, particularly sever in calcareous soils (about 30% of world´s land surface). The current use of synthetic iron-chelates to prevent or correct iron-deficiency in plants raises environmental concerns due to their poor biodegradability. Thus, new, more environmentally-friendly efficient solutions are needed to solve iron deficiency-induced chlorosis (IDIC) in crops grown in calcareous soils. In this work, a new green freeze-dried iron fertilizer was produced (patent submitted) from a culture of A. vinelandii containing siderophores of a natural source able to bind iron at pH 9. Soybean plants cultivated under calcareous soils and treated with the green iron-fertilizer responded more significantly and comparable to the positive control, ethylenediaminedi(o-hydroxyphenylacetic) acid, than those treated with the negative control, when evaluated by their growth (dry mass) and chlorophyll concentration (SPAD index). On average, iron content was also greater on green iron-fertilizer treated plants than on negative control treated ones. Results suggest that the freeze-dried product, prepared from A. vinelandii culture, can be a viable alternative for mending IDIC of soybean plants grown in calcareous soils.