Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/29/2003
Publication Date: 7/1/2004
Citation: Wang, Z., Kelly, J.M., Kovar, J.L. 2004. In situ dynamics of phosphorus in the rhizosphere solution of five species. Journal of Environmental Quality. 33:1387-1392. Interpretive Summary: Recently, soil conservation and water quality advocates have been promoting the use of plant and tree buffers to filter nutrients and sediment from runoff water and near-surface groundwater, so that streams and lakes are not polluted. At this point, we do not fully understand the role of plant uptake in controlling soluble phosphorus losses, because our understanding of the dynamics of P in soil solution around roots is limited. In this study, we used a micro-sampling technique to measure spatial and temporal changes in soil solution P in the rhizosphere of five plant species (corn, soybean, smooth bromegrass, switchgrass, and cottonwood). At the end of ten days of measurements, we found that corn, cottonwood, and smooth bromegrass were more effective in depleting P from soil solution. This suggests that the plant species used in a buffer will affect its ability to remove soluble P. These results should be of great interest to commercial growers and conservationists, as well as the fertilizer industry.
Technical Abstract: Root activity can modify the chemistry of the rhizosphere and alter phosphorus (P) availability and uptake. However, until recently, relatively little was known about the dynamics of soil solution P at the root surface because of our inability to measure in situ changes in solution P at the plant root. A mini-rhizotron experiment with corn (Zea mays L. cv. Stine 2250), soybean (Glycine max L. cv. Pioneer 3563), cottonwood (Populus deltoids L.), smooth brome (Bromus inermis Leyss), and switchgrass (Panicum virgatum L.) was conducted to measure the spatial and temporal dynamics of P in the rhizosphere solution of a fine silty, P-rich calcareous soil (solid phase total P concentration, 62 mg kg**-1; pH, 7.68) from western Iowa. Micro suction cups were used to collect samples of soil solution from defined segments of the rhizosphere, and Capillary Electrophoresis (CE) was used to determine the P concentration of the soil solution. At the end of 10 days, a decreasing P concentration gradient in soil solution toward the root was observed in corn, cottonwood, and smooth brome. No clear rhizosphere effect was observed for soybean and switchgrass. Statistical analysis indicated significantly lower solution P concentrations in the rhizospheres of corn (p=0.05), cottonwood (p=0.01), and smooth brome (p=0.01) compared to bulk soil solution. Results indicate that P depletion from rhizosphere soil solution depends on plant species. Under the conditions of this study, corn, cottonwood, and smooth brome were more effective in depleting solution P than soybean and switchgrass.