| Affiliation: | (1) Department of Engineering, Nova Scotia Agricultural College, 219 Resource Stewardship Building, 20 Tower Road, P.O. Box 550, Truro, Nova Scotia, B2N 5E3, Canada;(2) Brace Center for Water Resources Management, McGill University, Macdonald Campus, 21, 111 Lakeshore Road, Ste.-Anne-de-Bellevue, Quebec, H9X 3V9, Canada;(3) Semiarid Prairie Agricultural Research Center, Airport Road, Box 1030, Swift Current, SKS9H 3X2, Canada;(4) Department of Natural Resource Sciences, McGill University, Macdonald Campus, 21, 111 Lakeshore Road, Ste-Anne-de-Bellevue, Quebec, H9X 3V9, Canada |
| Abstract: | There is a growing interest in the adoption of conservation tillage systems [no-till (NT) and reduced tillage (RT)] as alternatives to conventional tillage (CT) systems. A 2-year study was conducted to investigate possible environmental consequences of three tillage systems on a 2.4-ha field located at Macdonald Research Farm, McGill University, Montreal. The soil was a sandy loam (0.5 m depth) underlain by a clay layer. Treatments consisted of a factorial combination of CT, RT, and NT with the presence or absence of crop residue. Soil NO3--N concentrations tended to be lower in RT than NT and CT tillage treatments. Denitrification and N2O emissions were similar among tillage systems. Contrary to the popular assumption that denitrification is limited to the uppermost soil layer (0–0.15 m), large rates of N2O production were measured in the subsurface (0.15–0.45 m) soil, suggesting that a significant portion of produced N2O may be missed if only soil surface gas flux measurements are made. The N2O mole fraction (N2O:N2O+N2) was higher in the drier season of 1999 under CT than in 2000, with the ratio occasionally exceeding 1.0 in some soil layers. Dissolved organic C concentrations remained high in all soil depths sampled, but were not affected by tillage system. |
