Sigua Gilbert C, Kang Woo-Jun, Coleman Sam W
USDA Agricultural Research Service, Subtropical Agricultural Research Station, Brooksville, FL 34601, USA.
J Environ Qual. 2006 Oct 27;35(6):2374-82. doi: 10.2134/jeq2006.0092. Print 2006 Nov-Dec.
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.
在美国东南部沿海平原地区，受1849年《沼泽地法案》的通过影响很大，许多湿地消失了，主要是农业活动排水所致。为了更好地了解湿地转化过程中土壤的化学响应，2002年和2003年夏季，从佛罗里达州普兰特市已转化的肉牛牧场和天然湿地采集了土壤岩芯样本。从天然湿地地点收集的数据用作参考数据，以检测1940年至2003年湿地转化为改良肉牛（Bos taurus）牧场后土壤性质的潜在变化。牧场土壤中总磷（TP）的平均浓度（284 mg kg⁻¹）显著（p ≤ 0.001）低于天然湿地土壤中的水平（688 mg kg⁻¹）。与相邻的天然湿地相比，排水63年后的肉牛牧场土壤表现出：（1）总有机碳（TOC）（-172 g kg⁻¹）、总氮（TN）（-10 g kg⁻¹）、钾（K）（-0.7 mg kg⁻¹）和铝（Al）（-130 mg kg⁻¹）减少；（2）土壤pH值（+1.8）、钙（Ca）（+88 mg kg⁻¹）、镁（Mg）（+7.5 mg kg⁻¹）、锰（Mn）（+0.3 mg kg⁻¹）和铁（Fe）（+6.9 mg kg⁻¹）增加；（3）钠、锌和铜无显著变化。湿地土壤中铝磷（Al-P）（435）、钙镁磷（CaMg-P）（42）、铁锰磷（FeMn-P）（43）和有机磷（Org-P）（162）的浓度（mg kg⁻¹）分别高于牧场土壤中的172、11、11和84 mg kg⁻¹。2003年湿地和牧场土壤中水溶性磷和氯化钾结合磷的水平相当。因此，本研究结果表明，即使由于有放牧的牛而添加了粪便和尿液，湿地转化为肉牛牧场也不是养分来源，尤其是磷和氮。
