Submitted to: Journal of Soils and Sediments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 2004
Publication Date: April 10, 2004
Citation: Sigua, G.C., Griffin, J., Kang, W., Coleman, S.W. 2004. Wetland conversion to beef cattle pasture: Changes in soil properties. Journal of Soils and Sediments. 4(1):4-10. Interpretive Summary: The study described in this paper was conducted on a 162-ha historic wetland that was largely drained and converted to improved beef cattle pasture in the early 1940's, largely influenced by the passage of the Swamp Land Act of 1849. The converted wetland and the reference adjoining wetland was now a part of a Hillsborough County Environmental Land Acquisition and Protection Program (ELAPP) parcel owned by the city of Plant City, Florida. This parcel is named 'McIntosh Park' and is located in northeastern Hillsborough County, Florida. A plan to restore this wetland is underway. The city of Plant City and the Southwest Florida Water Management District in Florida are presently engaged in a wetland creation and restoration of about 41 ha of the 162 ha McIntosh Park property. The current study was begun to establish the existing conditions of the converted pasture prior to beginning restoration. The objectives of this study were: (1) to evaluate the changes in soil properties as a result of the conversion of wetland to improved beef cattle pasture in 1940; (2) to establish useful baseline information on soil properties in pasture and adjoining reference wetland prior to restoring and converting pasture back to its original wetland conditions; and (3) to assess the impact of beef cattle grazing on some soil properties of the converted wetlands. Overall, conversion of wetland had obvious and significant effects on soil carbon, pH, nitrogen, phosphorus, and extractable nutrients. Results of our study have shown a decrease in TOC, TN, WSP, and K and an increase in soil pH, Ca, Mg, Mn, and Fe. These results are critical in establishing useful baseline information on soil properties in pasture and adjoining reference wetland prior to restoring and converting pasture back to its original wetland conditions.
Technical Abstract: Largely influenced by the passage of the Swamp Land Act of 1849, many wetlands have been lost in the coastal plain region of southeastern United States primarily as a result of drainage to convert land for agriculture. While further wetland conversion or loss is universally acknowledged, the process continues with little public recognition of the causes or consequences. This study examined changes in soil carbon, pH, and Mehlich extractable nutrients in soils following conversion of wetland to beef cattle pasture. Eleven sites were sampled from the beef cattle pasture, and four sampling sites were established and sampled from the adjoining reference wetland. Data that were collected from the reference wetland sites were used as the reference/baseline data to detect potential changes in soil properties associated with the conversion of wetlands to beef cattle pastures from 1940 to 2002. Compared with the adjoining reference wetland, the beef cattle pasture soils in 2002, 62 years after being drained, exhibited: (1) a decrease in organic carbon, TOC (-172.3 g kg-1), nitrogen, TN (-10.1 g kg-1), water soluble phosphorus, WSP (-5.1mg kg-1), and potassium, K (-0.7 mg kg-1); (2) an increase in soil pH (+1.8 pH unit), calcium, Ca (+88.4 mg kg-1), magnesium, Mg (+7.5 mg kg-1), manganese, Mn (+0.3 mg kg-1), and iron, Fe (+6.9 mg kg-1); and (3) no significant changes in sodium (Na), zinc (Zn), copper (Cu), and aluminum (Al). In 2002, the amount of TOC and the concentration of soil organic matter (OM) in pasture fields were significantly lower than the current concentration in the reference wetland with average values of 7.8 ± 8 g kg-1 and 36 ± 26 g kg-1 and 180.1 ± 188 g kg-1 and 257 ± 168 g kg-1, respectively. It appeared that conversion of wetlands was proceeding toward a soil condition/composition like that of mineral soils.