Structural and hydraulic responses of humid tropical soils to lime and organic residue amendments

In humid tropical environments, where soils are characteristically acidic and low in organic matter, lime and organic residues have been used to improve soil quality. A systematic consideration of their interaction is, therefore, crucial for land-based ecosystem management. A 28-day incubation pot study was carried out to investigate the main and interactive effects of lime and organic residue type (corn stover and vermicompost) on aggregate stability under rapid wetting (WSAr), saturated hydraulic conductivity (Ksat), and soil water repellency (SWR) on three acidic soils with contrasting clay content from Trinidad: Cunupia (Aquic Hapludalfs), Sangre Grande (Fluvaquentic Endoaquepts), and Talparo (Aquertic Eutrudepts). Organic residue had a significant (P≤0.001) increasing effect on WSAr and Ksat for all three soils, this being highest for corn stover and lowest for no residue. Lime and organic residue interactive effects were only significant (P≤0.05) for WSAr in the Cunupia soil, where lime significantly reduced WSAr in the vermicompost and no residue, but not in the corn stover treatment. Soil water repellency increased with clay content and was highest in the lime–corn stover treatment of the Talparo soil. Overall, our results suggest that applying crop residue with lime may help minimise the short-term deleterious effects of lime on the structural and hydraulic properties of humid tropical soils. Nonetheless, future experiments with a wider range of soils and organic residues need to be carried out for a longer term to validate our results.