3. Nano and Microencapsulated Nutrients for Enhanced Efficiency Fertilizer

Enhanced Efficiency Fertilizer (EEF) is a current and very important subject. These systems offer an effective way to improve nutrient efficiency, minimize fertilizer losses by physical, chemical and biological processes, and reduce environmental impact. Examples of such materials are: Slow Release Fertilizer (SRF), which releases the nutrient slower than a common fertilizer; and Controlled Release Fertilizer (CRF), when factors as release rate, pattern and release period can be controlled during its use. Ideally, it should be faster at the beginning and slower during cultivation, to meet the nutritional need of the plant, which changes over the growing period. Those materials have been developed in diverse platforms such as: (i) the matrix itself acts as a fertilizer, or (ii) the fertilizer is dispersed in a matrix, and/or (iii) the fertilizer is covered or encapsulate by a matrix, typically, polymeric or composites materials. The first EEF developed were made with synthetic polymers, mainly acrylamide-based ones. However, recent studies have proposed the use of environmentally friendly materials such as biodegradable polymers, clay minerals and calcium carbonate. The processes used to obtain EEFs are numerous, e.g. chemical and physical methods as polymerization, coacervation, coating, and (micro and nano) encapsulation. As the name suggests, encapsulation technique involves capsules preparation composed of a shell material completely around a chemical core material (nutrient). This shell provides a prolongation of nutrient release from the core. Once this shell is dissolved or ruptured the nutrient encapsulated is released. Even though encapsulation is not a novelty, its industry has rapidly innovated with new technologies applied to pharmaceutical, agricultural, cosmetic and food industries. In this chapter, we discuss the techniques to improve nutrient efficiency according to the materials and encapsulation methods used.