THE INFLUENCE OF CONSERVATION TILLAGE AND NITROGEN MANAGEMENT STRATEGIES ON NITROUS OXIDE EMISSIONS FROM EASTERN CANADA

摘要

Innovative management practices are required to increase N fertilizer efficiency and to reduce nitrous oxide and carbon dioxide emissions from agricultural soils. The objectives of this study were to evaluate the feasibility of using zone tillage and nitrogen fertilizer placement technology to reduce nitrous oxide and carbon dioxide emissions associated with com production on clay loam soils in Eastern Canada. A three year field study was established on a wheat-corn-soybean rotation with each phase of the rotation present in every year. Investigations were focused on the corn phase of the rotation. The tillage treatments following winter wheat involved fall moldboard plow tillage (15 cm depth), fall transtill (15 cm depth) and no-tillage. The N placement methods evaluated were a shallow (2 cm depth) and deep (10 cm depth) N placement. Nitrous oxide emissions were measured 53 times and carbon dioxide emissions were measured over 43 times in 3 growing seasons (April 15th to November 15th) using vented closed chambers. Averaged over all three tillage systems and site-years, shallow N placement (3.05 kg N·ha~(-1)) decreased N_2O emissions from the soil by 23% compared to deep N placement (3.97 kg N·ha~(-1)). When deep N placement was used, zone-tillage (3.02 kg N·ha~(-1)) resulted in 38% lower emissions than conventional moldboard plow tillage (4.86 kg N·ha~(-1)) and no-tillage (4.04 kg N·ha~(-1)·yr~(-1)) resulted in 17% lower N_2O emissions than conventional moldboard plow tillage. Tillage and N placement treatments did not affect CO_2 emissions. Hence both zone tillage and shallow N placement techniques are effective strategies for reducing N_2O emissions.