Techniques for encapsulating slow-release fertilizers using smart polymers: Towards controlled and sustainable release of plant nutrients: A review

Abstract:

This paper reviews recent advances in the encapsulation of slow- and controlled-release fertilizers with smart polymer technologies as an innovative approach towards enhancing nutrient use efficiency and sustainable agriculture. Conventional fertilizers suffer huge losses of nutrients by leaching, volatilization, and fixation which ultimately reduce the efficiency of the fertilizer and have serious environmental consequences like contamination of groundwater and eutrophication. The smart polymer coating can best cope with this problem by regulating the release of nutrients according to environmental stimuli such as temperature, soil moisture, and pH, thus synchronizing nutrient availability with plant physiological requirements. The paper covers classification and functional mechanisms of stimulus-responsive polymers, encapsulation and coating technologies, nutrient release kinetics, the influence of interactions between polymeric coatings and soil physicochemical properties, and the influence of soil microbiota on polymer degradation. It also discusses the present problems related to synthetic polymer residues and microplastic accumulation and stresses the switch to biodegradable biopolymers like carboxymethyl cellulose, alginate, and nano-chitosan. It further reviews the economic feasibility, future research directions, and recommendations for enhancing the application of smart fertilizer technologies. In general, smart polymer-based controlled-release fertilizers are a key element of climate-smart agriculture and a sustainable approach to enhancing agricultural productivity while reducing environmental impacts.