Combining grasses and legumes cover crops improved sandy soil physical quality

ABSTRACT In sandy soils, low organic carbon content and weak structural stability often constrain pore functionality, water availability, and gas exchange, highlighting the need for management strategies that improve soil physical quality. The aim of this study was to quantify the impact of cover crops on SOC, soil physical properties, and soil processes in a sandy loam dystrophic Ferralsol (Latossolo Vermelho-Amarelo Distrófico). The experiment followed a randomized complete block design composed of five treatments and five repetitions. The experimental treatments were: (1) Control (fallow plots subjected to weed desiccation), (2) G (single grass: Urochloa ruziziensis), (3) GG (two grasses intercropped: Pennisetum americanum + U. ruziziensis), (4) GL (one grass and one legume intercropped: P. americanum + Mucuna pruriens), and (5) MIX (two grasses and one legume intercropped: P. americanum + U. ruziziensis + M. pruriens). Undisturbed samples were collected from the layers of 0.00-0.10, 0.10-0.20, 0.20-0.40, and 0.40-0.60 m to determine physical indicators such as bulk density (Bd), total porosity (TP), field capacity (FC), permanent wilting point (PWP), plant-available water (PAW), and the soil water retention curve, pore size distribution, water storage capacity (FC/TP), saturated hydraulic conductivity (Ksat), air permeability (Kair), and pore continuity index (K1). Results demonstrated that, compared with the Control (absence of cover crops), GL (grass + legume), MIX (mixed species), and GG (grasses) improved air conductivity by 8, 3.5, and 2.9 times, and pore continuity by 5.8, 2.9, and 2.2 times, respectively. The MIX system led to a 39 % increase in SOC relative to the Control. Additionally, intercropping two grass species with one legume (MIX) and combining one grass with one legume (GL) resulted in a 19 % increase in plant-available water compared with the Control treatment. Importantly, these improvements in pore architecture occurred without significant changes in soil bulk density (Bd) or total porosity (TP), underscoring that cover crops can reorganize the pore network independently of mass–volume relationships. Combination of grasses and legumes (GL, MIX) has substantial potential to improve plant-available water and the overall soil physical quality of sandy soils.