|Claassen, Norbert - GEORG-AUGUST UNIVERSITY|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 7, 2009
Publication Date: August 1, 2009
Citation: Kovar, J.L., Claassen, N. 2009. Plant Growth and Phosphorus Uptake of Three Riparian Grass Species. Agronomy Journal. 101:1060-1067. Interpretive Summary: Planting grass filter strips and buffers to remove nutrients and sediment from runoff water and near-surface groundwater is being promoted by conservationists to prevent streams and lakes from being polluted. However, the role of plant uptake in controlling phosphorus (P) losses is limited by our incomplete understanding of differences in growth and P capture among the various grass species growing in buffers. This controlled-climate study showed that under low P conditions, reed canarygrass (Phalaris arundinacea L.) produced more harvestable biomass with higher total P content than either smooth bromegrass (Bromus inermis Leyss.) or switchgrass (Panicum virgatum L.). When grown under high P conditions, however, switchgrass produced more harvestable biomass with higher total P content than the other species. A separate study showed that when plants were abruptly exposed to high P conditions after growing under low P conditions, canarygrass provided the greatest potential for P removal. Assuming that relative differences in plant growth would hold under field conditions, results suggest that canarygrass and switchgrass would more effectively remove P with periodic harvests than would bromegrass. The results of this work will contribute useful information to commercial growers, local environmental groups, and Cooperative Extension and NRCS personnel interested in promoting buffers to help reduce the negative effects of agricultural production on water quality.
Technical Abstract: Riparian buffers can significantly reduce sediment-bound phosphorus (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 will 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 µM. Plants were harvested at approximately 0, 26, 40, and 53 days after transplanting. 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. When grown in 1µM P solution, shoot dry matter (DM) yield increased in the order bromegrass<switchgrass<canarygrass. When grown in 100µM P solution, shoot DM yield increased in the order bromegrass=canarygrass<switchgrass. Switchgrass was the only species that had higher P content in plants grown in the 100µM P solution than in the 1µM 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 1µM P solution to 100µM P solution. Shoot P concentration of switchgrass followed the same trend. Assuming that relative differences in root growth and function would hold for soil-grown plants, results suggest that canarygrass and switchgrass would more effectively deplete dissolved P than would bromegrass.