Comparative evaluation of leguminous and non-leguminous fodder grasses under Silveroak-pepper based agroforestry system in the Western Ghats

Agroforestry systems are recognized for their potential to enhance soil fertility, a critical factor for sustainability in regions like the Western Ghats. This study evaluated the comparative impact of leguminous and non-leguminous fodder grasses on soil chemical properties within an established Silveroak-Pepper (Grevillea robusta - Piper nigrum) based agroforestry system (AFS) compared to an adjacent sole crop (SC) control. The study was conducted in Sirsi, Karnataka, on acidic laterite soils. Four fodder species out of which two non-legumes, Guinea grass (Megathyrsus maximus) and Para grass (Urochloa mutica) and two legumes, Hedge lucerne (Desmanthus virgatus) and Stylosanthes (Stylosanthes hamata) were intercropped in a Randomized Complete Block Design. Soil samples (0-30 cm) were analyzed before and after the six-month experiment for pH, electrical conductivity (EC), soil organic carbon (SOC) and available N, P and K. Results indicated that the AFS consistently improved soil properties more than the sole crop. The AFS moderated soil acidity, with mean pH increasing from 5.52 to a range of 5.63-5.82, whereas the sole crop system only shifted from 5.29 to 5.33-5.48. SOC accumulation was highest under AFS, with Hedge lucerne (0.83%) and Guinea grass (0.82%) showing significant gains over the initial 0.77%. A clear distinction was observed in nutrient availability: the leguminous grasses, Hedge lucerne and Stylosanthes, recorded the highest levels of available nitrogen (108.51 and 105.44 kg ha⁻¹, respectively) and available phosphorus (34.40 and 34.89 kg ha⁻¹, respectively) in the AFS, demonstrating the benefits of N-fixation and P-solubilization. Non-leguminous grasses also contributed to fertility, with Para grass significantly increasing available potassium (194.19 kg ha⁻¹). These findings confirm that integrating fodder grasses, particularly legumes, is a viable strategy for enhancing soil fertility and nutrient cycling in Silveroak-Pepper agroforestry systems.