Hydrology and species-specific effects of Bacopa monnieri and Leersia oryzoides on soil and water chemistry

In an 8-week greenhouse experiment, Bacopa monnieri (water hyssop) and Leersia oryzoides (rice cutgrass) were compared for nutrient assimilation as well as soil and water chemistry under variable flooding regimes using a nutrient solution rich in nitrogen (N) and phosphorus (P). Soil redox potential decreased in flooded treatments; however, mesocosms containing B. monnieri remained aerobic for much of the study, while flooded mesocosms containing L. oryzoides became moderately reduced. Soils containing L. oryzoides were higher in nitrogen. Generally, effluent concentrations of PO4 were higher in B. monnieri mesocosms. B. monnieri immobilization of N and P was significantly less in below-ground tissues than L. oryzoides. P immobilization in L. oryzoides generally increased in response to flooding, while B. monnieri showed no detectable response. Results indicated that species-specific flood responses in plant nutrient status are due to differing interactions of B. monnieri and L. oryzoides with the soil environment. Additionally, L. oryzoides demonstrated greater P uptake than B. monnieri across treatments, resulting in decreased concentrations of PO4 3 in effluent. Although N was also affected by flooding and species, generalizations on N allocation within the system are difficult to describe due to the changes in species of N in response to oxidation–reduction gradients and biotic assimilation. Copyright  2009 John Wiley & Sons, Ltd.