Monday, 7 November 2005
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Tree Integration on Pastureland: Role of Silvopasture in Reducing Nutrient Pollution from Pasturelands in Florida.

Gerard Michel, Vimala Nair, Ramachandran P. K. Nair, and Samuel Allen. University of Florida, 118 Newins-Ziegler Hall, Gainesville, FL 32611

Transport of nitrogen (N) and phosphorus (P) from sandy soils that predominate the 4.5 million ha of beef cattle grazing lands in Florida is a major source of nutrient pollution of water bodies. We hypothesize that the presence of trees in grazing lands (silvopastoral systems) would help retain more P and nitrate-N in the system than in tree-less pastures because of increased nutrient uptake by the combined tree and grass roots, and thus reduce the amounts that could contribute to surface water pollution. This research was conducted on four slash pine (Pinus elliottii)–bahiagrass (Paspalum notanum) silvopasture systems located in Osceola (280 9' N, 810 10' W), Manatee (270 13' N, 820 8' W), Suwannee (300 24' N, 830 0' W), and Alachua (290 45' N, 820 33' W) counties in Florida. Using a staggered grid sampling procedure, 24 soil profiles were collected from each location during summer and fall 2004. The soil samples were collected by depth: 0–5, 5–15, 15–30, 30–50, 50–75, and 75–100 cm using a bucket soil auger. The soils in Manatee and Osceola counties are Spodosols, whereas those in Alachua and Suwannee are Ultisols. P, N (nitrate and ammonium-N), Fe (iron) and Al (aluminum) concentrations were determined in Mehlich 1 (soil test in Florida) extracts for each soil. The Phosphorus Saturation Ratio (PSR) [molar ratio of Mehlich 1-P and Mehlich 1 (Al + Fe) concentrations] of the soil, was used as the environmental soil P indicator. Preliminary results showed that silvopastoral systems had less P left in the soil. Furthermore, P loss from Ultisols was less than from Spodosols.

Handout (.pdf format, 9993.0 kb)

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