Soil Profile Distribution of Phosphorus and Other Nutrients following Wetland Conversion to Beef Cattle Pasture

Abstract

Largely influenced by the passage of the Swamp Land Act of 1849, many wetlands were lost in the coastal plain region of the southeastern United States, primarily as a result of drainage for agricultural activities. To better understand the chemical response of soils during wetland conversion, soil core samples were collected from the converted beef cattle pastures and from the natural wetland at Plant City, FL in the summers of 2002 and 2003. Data collected from the natural wetland sites were used as reference data to detect potential changes in soil properties associated with the conversion of wetlands to improved beef cattle (Bos taurus) pastures from 1940 to 2003. The average concentration of total phosphorus (TP) in pasture soils (284 mg kg(-1)) was significantly (p </= 0.001) lower than its levels in natural wetland soils (688 mg kg(-1)). Compared with the adjoining natural wetlands, the beef cattle pasture soils, 63 yr after being drained exhibited: (1) a decrease in TOC (-172 g kg(-1)), TN (-10 g kg(-1)), K (-0.7 mg kg(-1)), and Al (-130 mg kg(-1)); (2) an increase in soil pH (+1.8), Ca (+88 mg kg(-1)), Mg (+7.5 mg kg(-1)), Mn (+0.3 mg kg(-1)), and Fe (+6.9 mg kg(-1)); and (3) no significant change in Na, Zn, and Cu. Wetland soils had higher concentrations (mg kg(-1)) of Al-P (435), CaMg-P (42), FeMn-P (43), and Org-P (162) than those of 172, 11, 11, and 84 mg kg(-1), respectively, found in the pasture soils. The levels of water-soluble P and KCl-bound P were comparable between wetland and pasture soils in 2003. Results of this study therefore suggest that wetland conversion to beef cattle pastures did not function as a source of nutrients, especially P and N, even with manure and urine additions due to the presence of grazing cattle.