Lignin Modified Urea Fertilizer's Biodegradation and Nitrogen Release under Reduced Soil Condition

Abstract

Lignin is a natural biopolymer easily available in industrial waste and currently being used in slow release matrix improvements. Research work objective is to study the effect of 5% to 20% alkaline kraft lignin (AL) loadings on the biodegradation and nitrogen release in urea modified tapioca starch, acting as biodegradable slow release fertilizer (SRF) under reduced soil condition. Weight loss (%) of SRFs reduced from 76% to 35% with increasing %AL until day 28. Biodegradability (%) of SRFs affectively reduced at low 5-10%AL compared to high 15-20%AL. Nitrogen release was reduced with increasing the %AL in SRFs. Nitrogen release mechanism showed fickian diffusion mechanism (n<0.5) except for 10%AL (0.5<n<1). The lowest diffusion coefficient, 1.71 x 10 -8 cm 2 /s was observed in 10%AL. Fourier transformed infrared analysis of the biodegraded SRFs showed anhydroglucose ring asymmetric stretching vibration due to COC and COH (904-1140cm -1 ), lignin's aromatic ring stretching (1451-1500cm -1 ) and deformation of C-H in lignin's guaicyl ring or starch glucose ring (1162 cm -1 ). Lignin can effectively be used to improve nitrogen slow release and reduce biodegradability of SRFs under reduced soil.