Nitrate and pesticide leaching from a processing carrot production system in Nova Scotia

Abstract

Environmental concerns associated with the continuous application of manure on farmland include potential contamination of surface and subsurface aquatic ecosystems. Our objective was to explore the potential environmental impact of utilizing liquid hog manure (LHM) as a fertilizer in carrot (Daucus carota L.) production. The effects of LHM (169 kg N ha-1; 50% assumed to be available), inorganic fertilizer (IF) (NPK; 70-80-100 kg ha-1) treatments and herbicide (linuron) application on the quality of drainage water from a carrot production system in Nova Scotia were examined. Nitrate-N (NO3−-N) (1 mg NO3−-N L-1 ≈ 4.5 NO3− L-1) concentrations resulting from two applications of 70 t ha-1 of LHM and 70 kg N ha-1 as ammonium nitrate (34-0-0) applied to tile-drained plots were monitored over 2 yr. The average NO3−-N concentrations in the drainage discharge were slightly greater for the LHM treatment (14.4 mg L-1) compared to the IF treatment (12.9 mg L-1), but the difference was not statistically significant (P > 0.05). Most drainage and NO3−-N losses occurred outside the growing season (November-April), but average NO3−-N concentrations in the drainage discharge exceeded 10 mg L-1 both during and outside the growing season. Flow rates of drainage discharge were not significantly affected by the fertility treatments. Less than 0.1% of the linuron herbicide applied to the test plots leached into the drainage water over the study period. Carrot yields were unaffected by the fertility treatments. We conclude that LHM is potentially useful source of nutrients for carrot with minimal harm to the environment, under the rates and management practices used in this study. However, excessive rates of application and/or long-term (>10 yr) repeated applications of manure may negatively impact water quality. Key words: Daucus carota, amendment, leaching, manure, yield