Corn Cob Biochar Improves Aggregate Characteristics of a Tropical Sandy Loam

Core Ideas Amount of water‐stable aggregates increased after biochar amendment. Biochar decreased tensile strength of soil aggregates larger than 4 mm. Strength of smaller aggregates (<2 mm) increased after biochar application. Soil friability and workability increased with increasing biochar application rate. Most tropical soils are highly weathered and are vulnerable to soil erosion because of their poor aggregate characteristics. Soil aggregate characteristics are critical indicators of soil structural stability, and they have the propensity to influence soil physical behavior and functioning. In this study, we investigated the effect of corn cob biochar on the aggregate characteristics of a highly weathered tropical sandy loam. Biochar was incorporated at rates of 10 Mg ha ‐1 (BC‐10), 20 Mg ha ‐1 (BC‐20), and 20 Mg ha ‐1 + triple super phosphate (BC‐20+P) and the stability, strength, and friability of soil aggregates evaluated. Biochar increased soil organic C (SOC) by 28 to 66% and decreased electrical conductivity (EC) relative to the untreated soil. The fraction of water‐stable aggregates was significantly improved by 27 to 53% in biochar treatments compared with the control. Biochar decreased the tensile strength of the large aggregates (4–8 and 8–16 mm), but increased same in the smaller aggregates (1–2 mm) and consequently led to significant improvements in soil friability and workability in the BC‐20 and BC‐20+P treatments. In perspective, incorporation of biochar may offer the potential to arrest the rate of degradation in highly weathered tropical soils and salvage the decline in their physical quality by minimizing the effects of soil erosion.