Determinants of compost quality across 12 agroecological zones of Peru: the role of regional organic waste and climatic conditions

Abstract

Introduction: Composting is a cornerstone of the circular economy in agriculture; however, its efficacy is often undermined by limited knowledge regarding how agroclimatic variability influences compost quality under real-world conditions in megadiverse countries such as Peru. Methods: We monitored twelve composting processes over a 16-week period, established at agricultural experimental stations across 12 agroecological zones in Peru—spanning the arid coast, the high Andes, and lowland/high-jungle environments. The study utilized locally representative organic residues and employed a multisite observational design analyzed via generalized linear mixed models (GLMM). Results: High-Andean sites, characterized by low ambient temperatures and quinoa residues, exhibited the highest organic carbon retention and biological stability. In contrast, lowland jungle stations showed accelerated mineralization and suboptimal organic matter content (≈12%), failing to meet national standards. In coastal regions, guinea pig manure helped minimize lead accumulation; however, arsenic concentrations exceeded international safety limits (40 mg kg⁻¹) at certain stations. Furthermore, fixed effects (climate and process parameters) explained more than 67% of the variation in organic matter and nitrogen, while the agroecological context accounted for ≈23% of the variability in yield. Discussion: These findings indicate that compost quality is driven by non-linear interactions between temperature, humidity, pH, electrical conductivity, and regional residue composition, demonstrating that "one-size-fits-all" protocols fail to capture these complex dynamics.