Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2007
Publication Date: 11/1/2008
Citation: Schroeder, P.D., Kovar, J.L. 2008. Comparison of the Phosphorus Sorption Characteristics of a Conservation Reserve Buffer and an Adjacent Crop Field. Communications in Soil Science and Plant Analysis. 39(19&20):2961-2970. Interpretive Summary: To evaluate the ability of the surface soil in a 13-year-old Conservation Reserve Program (CRP) buffer to retain or release phosphorus (P), we compared the P chemistry in the buffer soil to that in an adjacent continuously cropped production area from which the buffer was created. From a laboratory study in which eight increasing incremental amounts of inorganic P fertilizer were added to soil samples collected from both the buffer and cropped areas, we found that the soil from the cropped area was actually able to retain more P than the soil from the buffer area, and that the soil from the buffer area maintained a higher concentration of P in soluble form. These results suggest that it may not be appropriate to assume that a buffer will act as a P sink simply because it is not receiving direct P fertilization. These results will benefit both commercial growers and conservation groups by providing information on the effectiveness of buffer areas to minimize potential P losses.
Technical Abstract: The United States Department of Agriculture’s Conservation Reserve Program (CRP) was established by the Food Security Act of 1985. Since its inception, thousands of acres of cropland in stream riparian zones have been converted to conservation buffers through the planting of trees and native grasses. The objectives of this study were to determine the phosphorus (P) sorption characteristics of the surface soil in a 13-year-old CRP buffer and an adjacent continuously cropped production area from which the buffer was created, and to assess differences in P sorption maxima, and P-buffering capacity between the sites. Phosphorus sorption was modeled with both the simple Langmuir and the two-surface Langmuir equations. There were significant differences in all P sorption parameters between the cropped area and the buffer over most of the depth increments studied. The cropped area soil had higher sorption max (Smax), binding energy (k), and P equilibrium buffering capacity (PEBC) than the buffer soil. However, the buffer had higher equilibrium P concentration (EPC). These findings imply that it may not be appropriate to assume that a buffer will act as a P sink simply because it is not receiving P fertilization. Any assessment of buffer or filter strip effectiveness for P retention should include an examination of the P sorption properties of the soils present.