Rhizoma peanut root-rhizome mass, growth, and decomposition under grazing or clipping management

Abstract

Belowground plant structures are integral to nutrient cycling in grassland ecosystems. However, relative to herbage responses, few studies have examined the belowground dynamics of warm-season perennial forages under different management practices. This study evaluated root-rhizome responses and decomposition dynamics of a perennial legume (rhizoma peanut [RP; Arachis glabrata Benth. ‘Ecoturf’]) under continuous stocking (Grazing) and 56-day clipping (Haying) intervals across three 56-day periods in 2018 and 2019. In 2019, root-rhizome mass was greater under Haying than Grazing in two out of three periods, peaking at 14,980 kg organic matter (OM) ha⁻¹. Conversely, root-rhizome N concentration was lower with Haying than Grazing (12 vs. 14 g kg⁻¹). Root-rhizome growth rate was greater in 2018 than in 2019 (18.0 vs. 10.5 kg OM ha⁻¹ day⁻¹). In 2019, Grazing exhibited greater biomass (0.0013 vs. 0.0010 g g⁻¹ day⁻¹) and N (0.0016 vs. 0.0011 g g⁻¹ day⁻¹) decay rates than Haying. Root-rhizome N pools for 2018 and 2019 averaged 159 and 192 kg N ha⁻¹, with 86% and 93% N remaining post-incubation, respectively. During a 56-day period, N disappearance was 22.3 kg N ha⁻¹ in 2018 and 13.4 kg N ha⁻¹ in 2019, equating to 70 and 40 kg N ha⁻¹, respectively, over the 168-day growing season. With RP covering 30% of the pasture, root-rhizomes contribute an estimated 12–21 kg N ha⁻¹ per season. Root-rhizome dynamics in RP were influenced by defoliation management, though responses varied between years.