SURFACE-WATER QUALITY IMPACTS OF TILLAGE PRACTICES UNDER LIQUID SWINEMANURE APPLICATION

Field studies were conducted to investigate the effects of tillage pra ctices on the saturated hydraulic conductivity, and quantity and quali ty of surface runoff water resulting from the application of the liqui d swine manure as a fertilizer. As part of the study, infiltration exp eriments were conducted on silt-loam soil with no-tillage (NT) and dis k tillage (DT) practices. Liquid swine manure was applied on test plot s, and the rainfall was applied by the portable rainfall simulator. Th e infiltration data was analyzed for the saturated hydraulic conductiv ity (K-6) and runoff volume determinations. The surface runoff water w as analyzed for total N, total P, ammonia, and nitrate concentration d eterminations. The study indicated that the tillage had significant ef fects on K-6, and quantity and quality of runoff water. The K-6 values of the NT plots were found to vary from 0.693 to 1.734 mm/min, with a mean of 1.494 mm/min, while they varied from 1.056 to 2.543 mm/min, w ith a mean of 2.231 mm/min in the DT plots. The total N, total P, ammo nium nitrogen and nitrate nitrogen concentrations were lower in runoff generated from DT plots, compared to that from the NT plots. The chem ical concentration levels were significantly different in runoff water s collected one-day after manure application than in those collected 4 0-days after the manure application. Study suggested that the DT pract ice must be preferred over the NT practice if liquid swine manure is u sed as the fertilizer. The study is further continued to assess the lo ng-term impacts of swine manure application and tillage on the quantit y and quality of surface runoff water.