LONG-TERM BIOSOLIDS APPLICATION IN THE TEXAS COASTAL PLAIN

K-3 Resources, Inc. manages two sites in the Texas Gulf Coastal Plain that have been used for land application of biosolids generated in the Houston metropolitan area since the 1980's. Annual compliance data used to monitor the biosolids and soil conditions are available to evaluate impacts to both sites. Based on this information, long-term biosolids recycling to both sites has resulted in improved soil conditions, while producing quality forage. Biosolids pollutant concentrations (mg/kg) and soil pollutants levels (kg/ha) remain relatively low compared with criterion contained in 40 CFR 503. In addition increased soil organic matter should stimulate soil microbial activity, which in turn will improve soil structure, soil aeration, soil water holding capacity, and fertility.Because pollutants have been reduced to trace levels and pathogens controlled through technology and regulations, biosolids have become, simply, another nutrient source available for agriculture. However, as with any other manure or fertilizer, long-term biosolids application may eventually result in excessive soil P levels. Since P does not usually leach from the soil surface, these levels do not generally pose a threat to groundwater. However, this source can be a threat to surface waters when dissolved in runoff or contained in sediments transported by erosion. Implementing a nutrient management can minimize this potential danger.