Plant residues ameliorate pH of agricultural acid soil in a laboratory incubation: A meta-analysis

Background:The effect of plant residues on the pH of agricultural acid soil varies markedly across numerous studies, which has been attributed to differences in plant residue characteristics, soil initial properties, and experimental conditions. Aims: The aim of this study was to address the need to form a unified framework for the relationship between plant residue incorporation and acid soil pH in agricultural systems. Methods: A systematic compilation of data was performed through a keyword search in the Scopus database, which yielded 221 independent pairwise comparisons of soil pH across 23 published articles utilizing laboratory incubations. These data were then used to form a consensus on the effect of plant residue on acid soil pH via a meta-analysis approach. Results: 221 pairwise comparisons, 91.4% of the cases showed a positive effect of plant residue in increasing acid soil pH. Overall, plant residue application significantly improved soil pH of acid soil (p <= 0.05) by 12.4% +/- 1.0% regardless of the heterogeneity in plant, soil, and experimental attributes between studies. Our analysis also revealed that total alkalinity (>= 80 cmol kg(-1)) and N (>= 10 g kg(-1)) of plant residue provide the optimal ameliorative effect. This ameliorative effect is more pronounced in extremely acidic soil (pH 3.5-4.4) than at soil with pH > 5.5. Conclusions: The insights gained through this meta-analysis demonstrated the interplay between different plant residue, soil, and experimental attributes, which collectively influence the ameliorative effect of plant residue application to the pH of agricultural acid soil.