Browsing by Subject "Watershed management -- Texas"
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Item Biosolids application on southwest Texas rangelands: its influence on the soil and sediment properties and on runoff water quality(Texas Tech University, 1998-12) Rostagno, Cesar MarioWe assessed the effects of surface biosolids application date (Jan and Jul 95 and 1996) and rate (0, 7, 18, 34, and 90 Mg ha^-1) on soil physical and chemical properties, infiltration rate (IR), sediment production (SP) and quality, and runoff water quality from shrubland (Ustic Calciargid) and grassland (Vertic Paleargid) soils. Between July and October of 1996 we applied simulated rainfall to 0.50 m^2 plots with a single-nozzle rainfall simulator for 30-min at a rate of 160 mm hr^-1. All of the runoff and sediments were collected at 5-min increments. In the two soils, organic matter and IR increased; bulk density and SP decreased as rate of biosolids application increased. In the shrubland soil and for the plots treated in Jan 95 with 90 Mg ha^-1 IR increased 4.5 times with respect to the control plots. For the same soil and treatment, SP decreased 22-fold. The eroded sediments of the shrubland soil for the 18 Mg ha^-1 biosolids applied in Jan 95 had the highest amount of organic matter For this soil, the enrichment of total N in the eroded sediments of the control plots was 40%, and increased to 1600% in the 18 Mg ha^-1 plots treated in January, 1995. Also, Cu and Zn in the eroded sediments increased from 96% and 160% in the control plots, to 1660% and 1460% in the treated plots, respectively. The concentration of NH4, NO?, PO4, Cu, and Mn in the runoff water were similarly affected by biosolids application, increasing with rate and decreasing with time of biosolids postapplication in the two soils. PO4 and NH4 should be the main compounds considered when surface-applying biosolids since their concentrations are well above the threshold for eutrophication and the recommendations for effluent discharge levels into surface waters Except for Mn that was above the US-EPA established secondary maximum contaminant level for drinking water in the plots treated with the higher rates of biosolids, the rest of the analyzed elements and compounds were either below the detection limits or within the US-EPA established .standards.