Pre-Terra Preta formulation improves forage quality of Pennisetum purpureum cv. Mott on marginal land

Abstract

Marginal tropical soils, particularly Dystric Histosols, pose severe constraints for sustainable forage production due to their low fertility, poor nutrient retention, and low organic matter content. This study evaluated the effect of pre‑Terra Preta formulations (biochar combined with organic matter and microbial inoculants) on biomass yield and forage quality of Pennisetum purpureum cv. Mott in Dystric Histosols of South Kalimantan, Indonesia. Treatments consisted of pre-Terra Preta formulations containing 0%, 20%, 40% and 60% biochar within the formulation matrix (w/w), applied at rates of 10, 20, and 30 tons ha-1. Biomass yield was evaluated using nested ANOVA, whereas forage quality attributes (proximate composition, fiber fractions) and soil chemical properties were assessed using Pearson correlation and principal component analysis (PCA). Results demonstrated that biomass yield increased significantly only at ≥ 40% biochar, with the strongest effect observed at 60% biochar, producing nearly a fourfold increase relative to the control. Correlation analysis revealed strong internal coherence among fiber fractions and coordinated relationships among soil nutrient variables, while associations between soil chemical properties and forage quality traits were generally moderate. PCA further highlighted two dominant gradients: PC1 associated with structural fiber fractions, and PC2 reflecting soil fertility variables, underscoring the multivariate nature of soil–plant interactions. Overall, findings demonstrated that pre‑Terra Preta formulations substantially enhanced forage biomass productivity and influenced forage quality traits in marginal tropical soils. By identifying the threshold effect of ≥40% biochar and the optimal impact at 60%, this study provides practical guidance for rehabilitating degraded landscapes and strengthening the resilience of livestock systems in tropical regions.