Abstract
Phosphorus from fertilizers accumulates in the surface soil layer and runs off because of rainfall. In this study, we investigated the size-dependent particulate phosphorus concentration in surface runoff to elucidate the mitigating effect of sod culture using rattail fescue [Vulpia myuros (L.) C.C. Gmel.] on phosphorus loss from soil in a citrus orchard. Particles of 1-10 µm in diameter comprised 86% of suspended solids in sod culture, whereas particles >10 µm in diameter comprised 1%. In clean cultures (bare soil surface), particles of 1-10 µm in diameter comprised 62% and particles >10 µm in diameter comprised 32% of suspended solids. The phosphorus concentration in the surface runoff from sod culture was lower than that from clean cultures in all experiments. The phosphorus concentrations in the sod cultures were 33%, 36%, 6.3%, and 5.8% compared to those in clean cultures, when the particles were <0.45 µm, 0.45-1 µm, 1-10 µm, and >10 µm in diameter, respectively. This study has shown that sod culture reduces the size-dependent particulate phosphorus concentration in surface runoff in all experiments and that sod culture has mitigating effects on the loss of particulate phosphorus of various sizes.
