Novel Biodegradable Chelating Agents for Micronutrient Fertilization

Serious concerns about the negative impact of ethylenediaminetetraacetic acid (EDTA) on the environment resulted in severe restrictions imposed on this compound in many countries. One of the main concerns is related to the use of EDTA in agriculture as a chelator in microelement fertilizers: being introduced directly into the sawing fields, it penetrates into groundwater, with no chance to be captured/recycled. Respectively, there is an active search for environmentally friendly, biodegradable alternatives for this chelator. In this study, we proposed a biodegradable chelating agent, 2-((1,2-dicarboxyethyl)amino)pentanedioic acid (IGSA). It was synthesized in accordance with the principles of "green chemistry" from readily available nonhazardous precursors using water as a solvent; in addition, the method yields literally no waste. The synthesized chelator in the form of the crude reaction mixture was further used for preparing a multicomponent micronutrient fertilizer (B, Zn, Fe, Cu, Mn, and Mo). The fertilizer was shown to be highly biodegradable (72% in 28 days), while the EDTA-based product degraded only by 13%. The plant growing efficiency was tested on lettuce in the greenhouse experiments. The results were compared against the known commercial fertilizers based on EDTA and iminodisuccinic acid (IDS). The newly developed IGSA-based fertilizer significantly outperformed the EDTA-based fertilizer in lettuce biomass (1.4 and 1.6 times for root and foliar application, respectively). The total mineral uptake was almost two times higher (1.9 and 1.8 times for root and foliar treatments, respectively) compared to the EDTA-based complex and even slightly higher (1.2 and 1.1 times, respectively) compared to the IDS-based complex. Our work opens the doors for the industrial scale production and application of this fully "green", inexpensive microelement fertilizer that has the potential to replace the EDTA-based products.