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EFFECTS OF ORGANIC CARBON APPLIED AS DAIRY EFFLUENT ON NITRATE LEACHING FROM A SANDY GRASSLAND SOIL: AN N STUDY
Citation:
Silva, R. G., E E. Jorgensen*, K. C. Cameron, AND H. J. Di. EFFECTS OF ORGANIC CARBON APPLIED AS DAIRY EFFLUENT ON NITRATE LEACHING FROM A SANDY GRASSLAND SOIL: AN N STUDY. Presented at Southern Branch of American Society of Agronomy, Mobile, AL, February 01 - 04, 2003.
Impact/Purpose:
To inform the public.
Description:
Nitrate (NO3-) leaching from dairy cattle urine is considered to be a major cause of surface and ground water contamination. Previous studies have shown that carbon sources can reduce nitrate leaching by enhancing denitrification. The objective of this work was to study the impact of cattle urine-N (15N labeled) on NO3- leaching when it was applied to pasture soil with or without an organic carbon source, e.g. dairy effluent (DE). Nitrate leaching was measured for two years using lysimeters. The lysimeters were extracted from Templeton sandy loam soil (Udic Ustochrept) with a perennial ryegrass/white clover (Lolium perenn/Trifoloum repens) mixed pasture. Nitrate concentration did not exceed the drinking water threshold limit during the two year period of the DE (400 kg N ha-1) treatment. In the first year application of DE resulted in significantly lower (P < 0.05) NO3- leaching (10 kg N ha-1) compared with urea (18 kg N ha-1). Average NO3- concentrations were lower when DE was combined with urine than urine alone in the first year, but the results were opposite in the second year. Nitrate leaching loss from the urine plus DE treatment was 113 kg N ha-1 in the first year. Even though the total leaching loss from urine plus DE (90 kg N ha-1) was higher than urine alone (77 kg N ha-1) in the second year, the annual percentage of 15N recovered in the leachate from the urine plus DE (9%) was not significantly different from the urine alone (6%) treatment. Annual percentage of 15N uptake by the pasture from urine plus DE treatment was 29% and was significantly less than urine alone treatment (39%) (P < 0.01). The apparent denitrification loss was slightly higher in the urine plus DE (13%) compared with the urine alone (5%). The greater contribution of urine 15N on NO3- leaching when urine was combined with DE (98%) rather than urine alone (83%) reveals that the application of DE (organic C) did not lower nitrate leaching from cow urine.