Bioactive Coating With Low Reactive Sources for Application as Multi-nutrient Fertilizer Granules

Abstract Fertilization is essential to provide suitable conditions for plant development and crop productivity, but the environmental cost of fertilizer production is a drawback for achieving a sustainable agriculture. Using unprocessed (raw) nutrient sources such as elemental sulfur (S0) and mineral oxides (ZnO, MnO, CuO) as fertilizers reduces the environmental impact, although they are not readily available to plants. Thus, we developed a polymeric coating material based on gelatinized starch loaded with S0 and oxides, and selected microorganisms – Aspergillus niger and Aciditiobacillus thiooxidans – aiming at a multi-nutrient fertilizer in which the biological components improve the solubility of the low reactive nutrient sources. The acidifying capacity of both microorganisms led to a synergic release and increased the availability of micronutrients and the elemental sulfur oxidation rate. For instance, the polymeric coating composition enabled a sulfate release of up to 76.4 and 71.3% for A. niger and A. thiooxidans, respectively. This innovative system can effectively supply nutrients to plants through the use of cheap and low reactivity nutrient sources with the advantage that it can be applied on currently used fertilizer granules, making easier the adoption by producers.