Effect of Phosphorus Concentration on Growth of Muhlenbergia capillaris in Flooded and Non-Flooded Conditions

Abstract

Research was conducted to evaluate the effect of phosphorus (P) concentration in irrigation water on growth of a southeastern U.S. native grass Muhlenbergia capillaris in flooded and non-flooded conditions. Plants of Muhlenbergia capillaris (Lam.) Trin. (gulf muhly grass) growing in 3.8 liter (1 gal) containers in 85:15 sand:peat were flooded to the substrate surface for 0 (non-flooded) or 3 days (flooded). Between flooding events, plants were drained for 6 d with no additional irrigation. The flood-drain process was repeated five times. Non-flooded plants were hand watered as needed. Plants were irrigated (non-flooded) or flooded with one of several tap water solutions, each with a different P concentration ranging from 0 to 0.8 mg·liter−1 (ppm) P (hereafter referred to as P irrigation rate). The experiment was repeated once (total two runs). Shoot dry weight (SDW) root dry weight (RDW) were higher in non-flooded plants than in flooded plants in both runs. Shoot dry weight increased linearly with an increasing P irrigation rate, while RDW changed cubically with increasing P irrigation rates in run 1 (no effect on either in run 2). Phosphorus concentration in leachate increased with increasing P irrigation rate in run 1 but not in run 2. Phosphorus concentration in leachate was usually higher in flooded plants than in non-flooded plants in both runs. All plants maintained root and shoot growth when flooded suggesting M. capillaris would be appropriate native species for rain gardens or bioretention areas. Phosphorus concentrations in leachate were lower than what was applied indicating P was removed via plant uptake or substrate adsorption or both.