2nd UF Water Institute Symposium Abstract

Submitter's Name	Debashish Goswami
Session Name	Poster Session: Hydrologic, Biogeochemical and Ecological Processes 2
Category	Hydrologic, biogeochemical and ecological processes
Poster Number	218
Author(s)	Debashish Goswami,  University of Florida
	Sanjay Shukla,  University of Florida
	Wendy Graham, University of Florida
	Alan Hodges, University of Florida
	Mary Christman, University of Florida
	Effects of cattle exclusion best management practice on Phosphorus and Nitrogen discharges in the Lake Okeechobee basin
	A study was conducted in a beef-cattle ranch to evaluate ditch fencing and culvert crossing as a best management practice (BMP) to reduce nutrient loadings within the Lake Okeechobee basin. The BMP was implemented within a 170 m ditch section in a ranch. The loadings and concentrations of Total Phosphorus (TP) and Total Nitrogen (TN) were compared for one pre-BMP (June-October, 2005) versus three post-BMP periods (June-October, 2006-08). During the pre-BMP period, P loading was 123.10 kg higher at downstream as compared to that at upstream from the BMP site. During the post-BMP periods in 2006 and 2008, downstream loadings of P were 17.31 and 88.03 kg lower as compared to those at upstream from the BMP site. Downstream P loading was 35% higher than that for the upstream during the pre-BMP period while downstream P loadings were 32 and 11% lower during the post-BMP periods of 2006 and 2008, respectively. There were net reductions of N loads at the BMP site during 2006 and 2008. Unusually dry conditions during 2007 resulted in the addition of P and N at the BMP site, probably due to the release of P and N from soil and aquatic plants. Considering the variability in rainfall and flows during the study period, three scenarios for P reductions were considered: conservative, moderate and liberal. The conservative estimate was the average P reduction for all the three post-BMP periods. The moderate estimate excluded the post-BMP2 when P was added at the BMP site. The liberal estimate considered only post-BMP3 when the P loading reduction was highest. The economic analysis of the BMP indicated that the cost for per kg of P removal for the conservative, moderate and liberal scenarios were $22.05, $12.93, and $7.74, respectively per kg of P.