Effect of tropical millipede Rhinocricus botocudus in the degradation and maturity of coffee residues

Abstract

In Brazil, approximately 3 tons of dry mass per hectare of coffee residues (CR), formed by leaves and branches <5 mm in diameter, were accumulated around the crops in the last harvests of the semi-mechanized crops. Thus, the production of substrates and organic fertilizers from the bioconversion of residues of coffee activity is an important theme in Brazil and in the world. The objective of the study was to investigate the effectiveness of the tropical millipede Rhinocricus botocudus on the degradation and maturity of coffee residues (CR). The presence or absence of R. botocudus were tested in five sampling times (0, 30, 60, 90, and 120 days) with three replicates (n = 3). The analyzed variables were: total C and N contents, lignin, cellulose, soluble C and N, soluble polyphenols, C of humic substances, and infrared analysis of humic acid (HA) and fulvic acid (FA). At the final incubation stage (120 days), the lowest values of cellulose, cellulose/lignin, and polyphenols occurred with R. botocudus. Infrared analysis of HA demonstrated that readily biode gradable structures, such as alcohols and short chain aliphatic molecules, were decomposed over time, consequently reflecting the increase of aromatic structures of greater stability. Compared to the control, these changes in HA were more evident in the presence of R. botocudus. The results of the present study suggest that this millipede species modify the dynamics of degradation and humification of CR by accelerating the maturity of this residue.