Water quality improvements in the Upper North Bosque River watershed due to phosphorous export through turfgrass sod

摘要

The Upper North Bosque River (UNBR) watershed is under a Total MaximumDaily Load (TMDL) mandate to reduce Phosphorus (P) due to excess nutrients in thewatershed. To address these problems, Texas A&M University researchers havedeveloped a turfgrass sod Best Management Practice (BMP) to remove excess nutrientsfrom impaired watersheds. Turfgrass harvest of manure fertilized sod removes a thinlayer of topsoil with most of the manure applied P. Plot and field scale research hasdemonstrated the effectiveness of turfgrass to remove manure phosphorus (P). In orderto assess the impact of the turfgrass BMP on a watershed scale, the Soil and WaterAssessment Tool (SWAT) was used to predict water quality in the UNBR watershed.The SWAT model was modified to incorporate turfgrass harvest routines to predictmanure and soil P export through turfgrass sod and soil during harvest. SWATsimulations of the BMP predicted stream load reductions of 20 to 36% for P loads in theUNBR depending on the implementation scenario, an average reduction of 31% for totalN and 16.7% for sediment for all the scenarios, at the watershed outlet. The SWATmodel also predicted up to 176 kg/ha P removed per sod harvest when fertilized with100 kg manure P/ha, and 258 kg/ha of P removed per sod harvest when the manure Papplication rate was 200 kg/ha. In addition, depending on the implementation scenario,the turfgrass BMP could export between 262 and 784 metric tons of P out of the UNBRwatershed every year.Manure fertilized turfgrass has the advantage of slow releasing nutrients from thecomposted dairy manure, so it would not require any additional P for life. This meansreduced urban non-point source pollution and lower maintenance cost compared toregular sod. These modeling simulations complement the wealth of research that showsthe effectiveness of the turfgrass BMP.