科研之友
微信
新浪微博
Facebook
分享链接
摘要
Determining soil nutrient distribution in pasture with beef cattle operation is critical to identifying which area is at risk of nitrogen or phosphorus buildup and loading. Characterizing spatial variability of soil nutrients in relations to landscape location is important for understanding the effects of future land use change on soil nutrients and water pollution. We hypothesized that cattle congregation site may have higher concentrations of phosphorus and nitrogen than in the pasture and grazing site or the adjoining forest site. This study assessed levels of Mehlich-1 extractable P, total inorganic N, and soil P saturation in relation to landscape locations in subtropical beef cattle pasture. Soil samples were collected during the spring and fall of 2005 to 2007 from three 19 adjoining landscape sites that are associated with beef cattle operation. These sites consisted of three locations: congregation, grazing, and forest sites. The levels of extractable P, total inorganic N, and P saturation in soils varied with landscape location. Congregation site had the highest concentration of extractable P of 36.1 mg kg(-1), followed by grazing site of 17.7 mg kg(-1), and forest site of 8.2 mg kg(-1). Spatial distribution of total inorganic nitrogen across the landscape was higher for congregation site (2.3 mg kg(-1)) than forest site (0.9 mg kg(-1)) and grazing site (0.7 mg kg(-1)). The overall spatial distribution of extractable P from congregation site to forest site can be described by P = -4.2x + 45.8; (R-2 = 0.97**); the best-fit models for total inorganic N was 0.04x(2) - 0.6x + 3.5; (R-2 = 0.89**) and for soil P saturation was -3.6x + 36.2; (R-2 = 0.92**). Results show that the levels of extractable P, total inorganic nitrogen, and soil phosphorus saturation were decreasing from the congregation site to forest site. Although our results may have had supported our hypothesis that congregation site typical on Florida ranchers have greater concentrations of extractable P than in grazing site and forest site, the average extractable P at all three landscape locations did not exceed the crop requirement threshold of 36 mg kg(-1) and the water quality protection threshold of 150 mg kg(-1). Our current pasture management including cattle rotation in terms of grazing days and current fertilizer application had thus no negative environmental impact on landscape with cow-calf operation.
- 出版日期2012-7
