Biosolids, materials resulting from domestic sewage treatment, are surface applied to forest soils to increase nutrient availability. Retaining streamside management zones (SMZs) can limit nutrient pollution of streams. We delineated 15 m SMZs along three intermittent streams in an 18-year-old Pinus taeda L. plantation. We applied biosolids outside the SMZ on one side of each of the streams maintaining the other side of the stream as control. We collected water samples from the three treated and six reference streams as well as from the perennial stream both upstream and downstream from the intermittent streams for 12 months following treatment. Along transects perpendicular to the treated streams, we collected overland flow samples, soil solution samples at 60 cm and extracts from ion exchange membranes (IEMs) placed in the surface soil. We found elevated nitrate concentrations outside the SMZ in the treated side soil solution samples, in which concentrations remained below 1.5 mg L-1. Nutrient concentrations outside the SMZ in treated side IEM extracts increased following biosolids application, returning to near control levels after one year. Nutrient concentrations in IEM extracts were not elevated adjacent to the streams. We observed elevated phosphorus concentrations adjacent to the stream in overland flow during one period on the treated side of the stream. Stream nutrient concentrations showed few differences downstream from the treatment with concentrations below 1.5 mg L-1. Our results indicate that a 15 m SMZ protected streams from nutrient pollution for the first year following biosolids application to adjacent forestlands. / Master of Science

Many states' Best Management Practices (BMP) programs established Streamside Management Zone (SMZ) widths based on limited or inadequate data with regard to nutrient fluxes from silvicultural activities. Previous studies in forested watersheds have shown slight post-harvest increases of several nutrients in streams. Also, in agricultural settings, increased nitrogen (N) and phosphorous (P) levels have been detected in streams. However, little is known about the effectiveness of recommended forested SMZ widths for controlling nutrient fluxes following fertilizer application. Diammonium phosphate (DAP) and urea fertilizers were applied to subwatersheds of 2 to 3 year-old loblolly pine (Pinus taeda L.) plantations upslope from SMZ study areas throughout Buckingham Co., VA. Three replications of four SMZ treatment widths (30.5m, 15.2m, and 7.6m plus a thinned 15.2m SMZ) were studied using surface water collectors, cation/anion exchange membranes, lysimeters, and stream grab-samples. Measurement devices were spaced symmetrically across the SMZ from the uphill SMZ edge to stream edge with grab samples being collected approximately 20m upstream and 20m downstream of the fertilized area. Little nitrogen and phosphorous movement was detected in surface water which was monitored using surface water collectors. Near-surface water flow sampling using ionic exchange membranes resulted in our most complete dataset and showed infrequent lateral ion transport in the litter and upper soil layers even after water passed over an approximately 1m wide, seeded firebreak located between the SMZ dripline and fertilized area. Results from lysimeter samples used to measure subsurface flow were limited due to dry conditions; however, the limited samples indicate that only minute levels of nitrogen and phosphorous are transported laterally via shallow subsurface and surface flow. Overall, sampling indicated that only minute quantities of nitrogen and phosphorous were ever transported from the fertilized clearcut to the riparian area. Results indicate that even a 7.6m wide SMZ with a seeded firebreak is adequate to protect streams from industrial fertilizer application in a relatively dry year, but wider SMZs may be necessary for other benefits. / Master of Science