ARS | Publication request: Modeling phosphorus capture by plants growing in a multi-species riparian buffer

Submitted to: Applied and Environmental Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 20, 2012
Publication Date: July 16, 2012
Citation: Kelly, J., Kovar, J.L. 2012. Modeling phosphorus capture by plants growing in a multi-species riparian buffer. Applied and Environmental Soil Science. DOI:10.1155/2012/838254.

Interpretive Summary: Planting grass and tree buffers to filter nutrients and sediment from runoff water and near-surface groundwater is being promoted by conservationists to prevent streams and lakes from being polluted. Previous research demonstrated that the potential phosphorus (P) removal by a mixed species buffer was 63% greater than from a bromegrass buffer, primarily because of fast-growing cottonwood trees. In this study, we used a validated mechanistic nutrient uptake model (NST 3.0) to explore the uptake of P during a single growing season in simulated buffer communities composed of varying percentages of cottonwood, switchgrass, and smooth bromegrass - three plant species commonly used in riparian buffers in the Midwestern U.S. Model estimates of P uptake over a single growing season ranged from 17 lb. P per acre for the smooth brome only to 22 lb. P per acre for cottonwood only, whereas simulated buffers with mixtures of trees and grasses were intermediate to the pure stands. Although a pure stand of cottonwood may be more effective in capturing dissolved P, grass communities will be more effective in retarding or preventing the loss of particulate P due to soil erosion. The results of this study will provide useful information to commercial growers, local environmental groups, Cooperative Extension, and the Natural Resources Conservation Service (NRCS) personnel interested in promoting buffers to help reduce negative effects of agricultural production on water quality.

Technical Abstract: The NST 3.0 mechanistic nutrient uptake model was used to explore phosphorus (P) uptake to a depth of 120 cm over a 126-d growing season in simulated buffer communities composed of mixtures of cottonwood (Populus deltoids Bartr.), switchgrass (Panicum virgatum L.), and smooth brome (Bromis inermis Leyss). Model estimates of P uptake from pure stands of smooth brome and cottonwood were 18.9 and 24.5 kg ha-1 respectively. Uptake estimates for mixed stands of trees and grasses were intermediate to pure stands. A single factor sensitivity analysis of parameters used to calculate P uptake for each cover type indicated that Imax, k, ro, and Lo were consistently the most responsive to changes ranging from -50% to +100%. Model exploration of P uptake as a function of soil depth interval indicated that uptake was highest in the 0-30 cm intervals, with values ranging from 85% of total for cottonwood to 56% for switchgrass.