Growth and phosphorus uptake of three riparian grass species

Riparian buffers can significantly reduce sediment-bound P entering surface water, but control of dissolved P inputs is more challenging. Because plant roots remove P from soil solution, it follows that plant uptake can reduce dissolved P losses. We evaluated P uptake of smooth bromegrass (Bromus inermis Leyss.), reed canarygrass (Phalaris arundinacea L.), and switchgrass (Panicum virgatum L.) grown in a flowing nutrient solution culture system with P concentrations of 1 or 100 µmol L–1. Plants were destructively sampled at approximately 0, 26, 40, and 53 days after transplanting (DAT). In a separate, concurrent experiment, we simulated the effect of an inflow of runoff with low or high dissolved P by switching a subset of pots approximately 40 DAT. When grown in 1 µmol L–1 P solution, shoot dry matter (DM) yield increased in the order bromegrass < switchgrass < canarygrass. When grown in 100 µmol L–1 P solution, shoot DM yield increased in the order bromegrass = canarygrass < switchgrass. Shoot P content was correlated with shoot DM yield; however, switchgrass was the only species that had higher P content in plants grown in 100 µmol L–1 P solution than in 1 µmol L–1 P solution. When solution P concentration was abruptly increased or decreased, P uptake was affected more than plant growth. Shoot P concentration of canarygrass increased more than 3.5-fold when the plants were switched from 1 µmol L–1 P solution to 100 µmol L–1 P solution. Shoot P concentration of switchgrass followed the same trend. The results of this solution-culture experiment suggest that canarygrass and switchgrass would more effectively deplete dissolved P than would bromegrass.