Use of turfgrass sod to transport manure phosphorous out of impaired watersheds
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Texas has developed a Total Maximum Daily Load (TMDL) for Phosphorous (P) in segments of the Upper North Bosque River (UNBR) which includes a mandate for a 50% reduction of soluble reactive P. The watershed's primary agricultural activity is dairy production and large quantities of manure are produced. One suggested Best Management Practice (BMP) is the export of P from impaired watersheds using turfgrass sod produced with composted dairy manure. The sod produced by this BMP would be transplanted to urban watersheds. Urban water quality may improve since the BMP sod does not need additional P fertilizer due to the release of the P in the composted manure. Field studies and model simultaneous studies are underway to assess the effectiveness of this BMP. Field research studies are examining the efficiency of P removal in turfgrass harvests as well as surface runoff losses. The Soil and Water Assessment Tool (SWAT) model is being used to simulate water quality in the UNBR watershed as well as the suburban watershed, Mary's Creek near Fort Worth, TX, that would receive the BMP sod. Initial results show that 46 to 77% of applied manure P can be removed in a single sod harvest. Also, sod grown with manure P rates of 190 kg P ha-1 can be imported without increasing runoff losses of total dissolved P to the importing watershed. The SWAT model has successfully been calibrated to simulate the measured flow and sediment from the UNBR and the Mary's Creek watersheds. The Nash-Sutcliffe model fit efficiencies are 0.86 for flow and 0.89 for sediment in the UNBR model and 0.69 for flow in the Mary's Creek watershed.
