RESUMO
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.
