Hydrology and species‐specific effects of Bacopa monnieriand Leersia oryzoideson 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. monnieriremained aerobic for much of the study, while flooded mesocosms containing L. oryzoidesbecame moderately reduced. Soils containing L. oryzoideswere higher in nitrogen. Generally, effluent concentrations of PO43−were higher in B. monnierimesocosms. B. monnieriimmobilization 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. monnierishowed no detectable response. Results indicated that species‐specific flood responses in plant nutrient status are due to differing interactions of B. monnieriand L. oryzoideswith the soil environment. Additionally, L. oryzoidesdemonstrated greater P uptake than B. monnieriacross treatments, resulting in decreased concentrations of PO4−3in 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.