Agricultural drainage ditches can deliver high loads of phosphorus (P) to surface water. Installation of filter structures containing P sorbing materials (PSMs), including gypsum, is an emerging practice that has shown promise to reduce these P loads. The objective of this study was to evaluate what effect soil amendment with gypsum would have on soil P concentrations and forms in a laboratory incubation experiment. Gypsum was saturated at two levels with P, and applied to a silt loam and a sandy loam at two rates. The treated soils were incubated in the laboratory at 25°C, and samples were collected on eight dates between 0 and 183 days after amendment. Spent gypsum application did not significantly increase soil water-extractable or Mehlich 3 P when applied at typical agronomic rates. This appears to be a viable strategy to remove P from agricultural drainage waters but does not appear to provide any additional P fertilizer value. 1. Introduction Accelerated eutrophication of the Chesapeake Bay has been identified as a priority natural resource concern [1]. According to the Chesapeake Bay Program Watershed Model Phase 4.3 agricultural sources account for 45% of the total phosphorus (P) delivered to the Chesapeake Bay [2]. The Delmarva Peninsula is comprised of the nine counties of the eastern shore of Maryland, Accomack and Northampton counties in Virginia, and the state of Delaware. The Delmarva Peninsula is home to a large concentration of poultry production, leading to a regional surplus of phosphorus (P). In the past, poultry manure was land applied based on crop nitrogen (N) requirements. However, because the P？:？N ratio found in manure is much higher than the P？:？N ratio required by plants, excessive P application has occurred resulting in elevated soil P concentrations [3]. The lower portion of the Delmarva Peninsula is dominated by coarse textured soils, shallow groundwater tables, and agricultural drainage ditches. Phosphorus leaching to groundwater is greatly increased in sandy soils with limited capacity to retain P, in soils with high P saturation, and in ditch drained soils containing preferential flow pathways [4]. This combination of hydrology and agricultural practices has led to P loading to surface water through shallow subsurface pathways and environmental quality issues [5]. One possible way to reduce phosphorus loss is to use by-product materials that can sorb phosphorus [6]. Phosphorus sorption is the process of adsorption and precipitation of P from dissolved to solid forms [7]. Phosphorus sorbing materials (PSMs) can provide a
References
[1]
B. Obama, Executive Order: Chesapeake Bay Protection and Restoration, 2009.
[2]
CBPO, “Sources of phosphorus loads to the Bay,” 2009, http://www.chesapeakebay.net/status_phosphorusloads.aspx?menuitem=19801.
[3]
D. H. Pote, T. C. Daniel, A. N. Sharpley, P. A. Moore, D. R. Edwards, and D. J. Nichols, “Relating extractable soil phosphorus to phosphorus losses in runoff,” Soil Science Society of America Journal, vol. 60, no. 3, pp. 855–859, 1996.
[4]
J. T. Sims, R. R. Simard, and B. C. Joern, “Phosphorus loss in agricultural drainage: historical perspective and current research,” Journal of Environmental Quality, vol. 27, no. 2, pp. 277–293, 1998.
[5]
P. A. Vadas, M. S. Srinivasan, P. J. A. Kleinman, J. P. Schmidt, and A. L. Allen, “Hydrology and groundwater nutrient concentrations in a ditch-drained agroecosystem,” Journal of Soil and Water Conservation, vol. 62, no. 4, pp. 178–188, 2007.
[6]
J. W. Leader, E. J. Dunne, and K. R. Reddy, “Phosphorus sorbing materials: sorption dynamics and physicochemical characteristics,” Journal of Environmental Quality, vol. 37, no. 1, pp. 174–181, 2008.
[7]
C. J. Penn, R. B. Bryant, P. J. A. Kleinman, and A. L. Allen, “Removing dissolved phosphorus from drainage ditch water with phosphorus sorbing materials,” Journal of Soil and Water Conservation, vol. 62, no. 4, pp. 269–276, 2007.
[8]
C. J. Penn, J. M. McGrath, and R. B. Bryant, “Ditch drainage management for water quality improvement,” in Agricultural Drainage Ditches: Mitigation Wetlands for the 21st Century, M. T. Moore and R. Kroger, Eds., Research Signpost, Kerala, India, 2010.
[9]
D. Stoner, C. Penn, and J. McGrath, “Phosphorus sorption onto by-products ina flow through setting: effect of material properties,” Journal of Environment Quality. In press.
[10]
C. J. Penn and J. M. McGrath, “Predicting phosphorus sorption onto steel slag using a flow-through approach with application to a pilot scale system,” Journal of Water Resource and Protection, vol. 3, no. 4, pp. 235–244, 2011.
[11]
C. J. Penn, et al., “Use of industrial by-products to sorb and retain phosphorus,” Communications in Soil Science and Plant Analysis, vol. 42, pp. 633–644, 2011.
[12]
R. B. Brennan, O. Fenton, M. Rodgers, and M. G. Healy, “Evaluation of chemical amendments to control phosphorus losses from dairy slurry,” Soil Use and Management, vol. 27, no. 2, pp. 238–246, 2011.
[13]
R. B. Clark, K. D. Ritchey, and V. C. Baligar, “Benefits and constraints for use of FGD products on agricultural land,” Fuel, vol. 80, no. 6, pp. 821–828, 2001.
[14]
M. E. Sumner, D. E. Radcliffe, M. McCray, E. Carter, and R. L. Clark, “Gypsum as an ameliorant for subsoil hardpans,” Soil Technology, vol. 3, no. 3, pp. 253–258, 1990.
[15]
K. D. Ritchey, R. F. Korcak, C. M. Feldhake, V. C. Baligar, and R. B. Clark, “Calcium sulfate or coal combustion by-product spread on the soil surface to reduce evaporation, mitigate subsoil acidity and improve plant growth,” Plant and Soil, vol. 182, no. 2, pp. 209–219, 1996.
[16]
K. H. Tan, Soil Sampling, Preparation, and Analysis, Taylor & Francis, 2005.
[17]
J. Murphy and J. P. Riley, “A modified single solution method for the determination of phosphate in natural waters,” Analytica Chimica Acta, vol. 27, pp. 31–36, 1962.
[18]
A. Mehlich, “Mehlich 3 soil test extractant: a modification of Mehlich 2 extractant,” Communications in Soil Science & Plant Analysis, vol. 15, no. 12, pp. 1409–1416, 1984.
[19]
D. A. Storer, “A simple high sample volume ashing procedure for determination of soil organic matter,” Communications in Soil Science & Plant Analysis, vol. 15, no. 7, pp. 759–772, 1984.
[20]
J. W. Tukey, The Problem of Multiple Comparisons, Princeton University, 1953.
[21]
F. J. Coale, “Descriptions of the soil test interpretive categories used by the University of Maryland soil testing laboratory,” in SFM-3, U. O. M. Extension, Ed., University of Maryland Extension, College Park, Md, USA, 1996.
[22]
J. M. McGrath and F. J. Coale, “Converting among soil test analyses frequently used in Maryland,” in SFM-4, U. O. M. Extension, Ed., University of Maryland Extension, College Park, Md, USA, 2006.
[23]
P. J. A. Kleinman, A. L. Allen, B. A. Needelman et al., “Dynamics of phosphorus transfers from heavily manured Coastal Plain soils to drainage ditches,” Journal of Soil and Water Conservation, vol. 62, no. 4, pp. 225–235, 2007.
