Biodegradation of N-fertilizer loaded on cellulose nanofibres to assess their potential use as a controlled-release fertilizer

Cellulose nanofibres (CNF) have emerged as advanced systems for controlled, smart delivery of N-fertilizer owing to their surface modification properties. However, to realize the true potential of this nanomaterial, its biodegradation analysis would be crucial to understanding its impact and fate when exposed to the environment. In this study, the main focus was to investigate the effect of N-fertilizer loaded CNF (electrostatic interaction between the negatively charged COO- group on CNF and the positively charged ammonium ion) on the microflora of the soil. The per cent weight loss of unloaded CNF and N-fertilizer loaded CNF in the soil indicated 54-62% decay within 36 days. The morphological changes during biodegradation, as estimated through SEM, indicated the formation of micro-cracks on the fibres. The cracks facilitate the colonization of microbes for their metabolic activities. Contrary to the unloaded CNF, the N-fertilizer loaded CNF was found to support microbial growth when subjected to burial in the soil, which is indicative of the ammonium chloride serving as the nitrogen supplement for the microflora. The content of available nitrogen remained constant in the case of the soil with the unloaded CNF (0.014%), whereas a slight variation was observed in the soil with the N-fertilizer loaded CNF (0.6%), which therefore indicates the controlled release of nitrogen after 36 days. Thus, this study is the first of its kind where the degradation of unloaded and N-fertilizer loaded CNF and their environmental impact have been investigated.