Recycling Animal and Plant Residues Through Vermicomposting: Nutrient Release, Organic Carbon Fractions, and Humate Quality Under Semi-Arid Conditions

Purpose: This study aimed to evaluate the availability of nutrients through different extraction methods, their potential mineralization, total carbon content, and carbon distribution in various organic carbon fractions. Additionally, it examined the characteristics of humates derived from distinct vermicompost formulations. Methods: The experiment followed a 6×4 factorial design, incorporating six treatments (combinations of cattle manure, goat manure, cashew leaves, and catanduva leaves) and four evaluation intervals (30, 60, 90, and 120 days of vermicomposting). The experimental units were arranged in a randomized block design with four replicates, using polyethylene containers under uniform environmental conditions. Results: The findings revealed that vermicomposts produced with cattle manure consistently displayed higher levels of total organic carbon and carbon in both labile and humified fractions of the organic material, regardless of the plant mixtures used. Nutrients showed greater availability in both the short and medium term, except for phosphorus and potassium, which were more readily available in vermicomposts based on goat manure in the short term. Conclusion: Cattle manure vermicomposts, regardless of the plant mixture, had higher levels of nutrients available in the short and medium term, except for P and K. Humates obtained from cattle manure-based vermicomposts exhibited elevated levels of carbon, hydrogen, nitrogen, oxygen, and carboxylic acidity, demonstrating a notable increase in aliphatic carbon groups and a higher degree of humification, coupled with lower aromaticity and minimal structural condensation. Highlights • Producers in the semiarid region have been producing vermicompost with animal and plant waste • The valorization of vermicomposted biowaste must have agronomic qualities within a given time. • The characteristics analyzed were: organic matter and fractions, nutrient and humate contents. • Vermicompost from cattle manure presented higher nutrient contents and total organic C and organic fractions. • Humates from cattle vermicomposts present higher composition of C, H, N and O, acidity and higher E4/E6 ratios.