As the need for practices more sustainable, agriculture has the challenge to decrease the environmental impact caused by fertilizer. Polymeric materials can contribute as a solution in the prospect of enhanced efficiency fertilizers (EEF), decreasing the loss, leaching, and volatilization of fertilizer. The present work sought the microencapsulation of micronutrients by starch as an EEF. First, we dispersed in a Turrax gelatinized starch and micronutrients (Fe/Cu/Mn). After, we dry the mono-elementary dispersions in a mini Spray Dryer (Büchi) using two-fluid nozzles. The morphology and particle size distribution of the materials was done by SEM images, and the swelling degree (SD) was determined in water. Microspheres and neat starch morphologies show the influence of the micronutrient and drying Fig 1. Neat starch has polygonal granular morphology and a surface with micro-cracks and pores. The fast solvent evaporation during starch drying caused non-sphericity and concave morphology common for spray-dried particles. Also, the microspheres morphology was altered according to nutrient, i.e., agglomerated and less spherical for Starch-Fe, concave for Starch-Mn, and more spherical with a micro-cracks surface for Starch-Cu. The SD behavior was Neat starch&lt; Starch-Fe&lt;Starch-Cu &lt;Starch-Mn &lt;Spray-dried starch and depend on gelatinization and particle size, i.e., the spray-dried starch swelled more due to the gelatinization, and the microspheres are more dependent on unimodal size distribution. According to mean size (spray-dried starch &lt;Starch-Fe &lt;Starch-Mn &lt;Starch- Cu &lt;Neat starch) we justify the lesser swell of Starch-Fe. Besides, Fe has a smaller hydration radius and a greater starch interaction (previous FTIR result), decreasing the mobility of polymeric chains, and lowering the swelling. In conclusion, it was possible to produce microspheres of starch and micronutrients with different morphology and particle sizes, which influences the swelling behavior, being an important aspect to maintain the soil moisture.

Morphology and swelling behavior of sustainable fertilizer based on Spray-dryer microspheres of starch and micronutrients

ACS Spring Meeting 2021

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