Effect of Iron Salt on Slow Fertilization Through Soy Protein-Based Matrices

Due to the increase in horticultural production intensive techniques are needed. These techniques generate soil degradation, since the natural recovery time between crops is insufficient. The usual way to solve this problem is the use of fertilizers, as they are effective in the short time available. Conventional fertilizers are highly soluble salts, allowing their absorption by plant roots. However, they are dumped on the soils in more quantity than plants need, thus, the excess of unassimilated nutrients contaminates both the soil and groundwater. The main objective of this work was to develop and evaluate an alternative to conventional fertilizers, creating slow-release matrices from a protein by-product to which iron was incorporated. To carry out a more complete study, iron was incorporated in concentrations of 2.5, 5.0 and 10 wt%, using two different salts: iron(II) sulfate heptahydrate (FeSO4·7H2O) and iron chelated with N,N′-ethylenediamine-bis (2-hydroxyphenyl) acetic acid (Fe-EDDHA). Several tests were performed to compare their mechanical properties, micronutrient release profile, water absorption capacity and biodegradability, as well as their final effectiveness in crops. The protein-based matrices with both salts incorporated presented good mechanical properties. However, Fe-EDDHA matrices had a greater water absorption capacity, while FeSO4·7H2O matrices were more efficient in their final application in plants and had a longer biodegradation time. In conclusion, protein-based matrices present a high potential for the slow release of iron, thereby improving crop properties.