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Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/30/2007 Publication Date: 4/1/2009 Citation: Bolster, C.H., Sistani, K.R. 2009. Sorption of Phosphorus from Swine, Dairy, and Poultry Manures. Communications in Soil Science and Plant Analysis. 40:1106-1123 Interpretive Summary: To increase crop yields phosphorus is often applied to agricultural fields in the form of fertilizer or animal manure. The over application of phosphorus, however, can result in the increase in phosphorus loads to surface waters which often times leads to eutrophication. In addition, the loss of phosphorus from the application area increases operating costs for the farmer. Therefore, considerable research has been undertaken to identify ways to prevent phosphorus loss from fields. One approach is to measure the mobility of phosphorus in the environment. This is often done by determining the degree of phosphorus saturation of a soil. If the soil is close to saturation then additional applications of phosphorus may not be retained by the soil and therefore will likely be lost. The degree of phosphorus saturation is often estimated using laboratory sorption studies in which phosphorus is added in the form of an inorganic salt. While this approach is useful when phosphorus is applied as an inorganic fertilizer, it is unlikely that it will provide a good estimate of saturation when phosphorus is applied in the form of animal manure. In this study we compared the ability of eight soils to sorb phosphorus in four different forms: inorganic salt, swine manure, dairy manure, and poultry litter. We found that the sorption of phosphorus was greatest for swine manure and least for dairy manure and the sorption of the inorganic phosphorus was in between the two. Our results demonstrate the need for using manure solutions when estimating the phosphorus sorption capacity of a soil when phosphorus is applied in the form of animal manure. Technical Abstract: Sorption studies are commonly used to obtain important parameters controlling the fate of phosphorus (P) in the environment. In most cases P is added as an inorganic salt to a pre-defined background solution such as CaCl2. The limitation to this type of study, however, is that the application of P is often in the form of animal manure. Given that manure leachate differs significantly in ionic composition, organic matter content, and pH from a CaCl2 solution, it is unclear whether sorption parameters obtained using a CaCl2 matrix will be representative of the sorption of manure-derived P in the environment. Therefore, the purpose of this study was to determine whether the sorption behavior of manure-P is similar to that of inorganic-P. Single-point P additions were conducted on eight soils with solutions containing CaCl2-P or manure-P (dairy, poultry, and swine). Factors expected to affect P sorption such as pH, specific conductivity, concentrations of organic matter, and ionic compositions of the solutions were measured. Results show that the sorption behavior of manure-P is different from that of inorganic-P and that the differences are dependent on soil texture and manure type. These results should caution anyone from using results from CaCl2-P sorption studies to estimate manure-P sorption and transport. |
