Do earthworms affect phosphorus availability to grass? A pot experiment

Abstract

Abstract The largest part of phosphorus (P) in soil is bound by the soil solid phase; its release to the soil solution therefore often does not meet the demand of plants. Since global P fertilizer reserves are declining, it becomes increasingly important to better utilize soil P. We tested whether earthworm activity can increase P availability to grass ( Lolium perenne L.) in a 75-day greenhouse pot experiment in a soil with low P availability. The full factorial design included two factors: P fertilization (control without P; phytate; and inorganic P) and earthworm population (control without earthworms; Lumbricus rubellus Hoffmeister, Lr; Aporrectodea caliginosa Savigny, Ac; and Lumbricus terrestris L., Lt). At four times during the experiment, aboveground plant growth and P uptake were determined. In a separate incubation experiment, earthworm casts and bulk soil were analyzed for inorganic and organic P in water extracts. We observed higher levels of dissolved P pools ( p −1 for inorganic P ( p  = 0.007) and from 0.18 to 1.30 mg L −1 for organic P ( p  = 0.007). After three harvests, presence of Lt significantly increased P uptake by grass to 44.1 mg per pot compared to 41.8 mg per pot for the control ( p  = 0.010). Plant growth increased from 15.68 to 16.85 g dry biomass per pot ( p