Greenhouse gas (GHG) emissions from nitrous oxide (N2O) are due in part to N inputs on agricultural land that are lost through the nitrification and denitrification processes. Earlier studies have shown that late spring is a critical time period compared to other seasons under maize (Zea mays L.) production, because soil nitrate is highly susceptible to leaching and denitrification, especially when the seasonal fertilizer needs have been applied early in the season. This study examined the effects of tillage (no-till; plow), fertilizer timing (full rate; starter only), rotation (maize after orchardgrass (Dactylis glomerata L.); continuous maize), and soil type (Muskellunge clay loam; Stafford loamy fine sand), on N2O losses as a result of a 50-mm late-spring precipitation event. N2O emissions and soil temperature were measured daily over a period of a week. In addition, soil nitrate content, soil physical properties and total N and C were measured. N2O emissions were highest on the second day after precipitation for all treatments. N2O losses were significantly higher on the clay loam compared to the loamy sand. Full early fertilization under no-till resulted in 4.7 and 2.3 kg N ha-1 greater cumulative N2O loss than starter-only fertilization on maize-after-grass and continuous maize, respectively. Under plow-till, full fertilization averaged 0.88 kg N ha-1 greater cumulative N2O loss than starter-only fertilization. Higher N2O losses under no-till compared to plow till were related to lower soil porosity and higher bulk density, and emissions under maize-after-grass were related to higher soil C levels. A cumulative GHG budget analysis indicated that increased N2O losses from no-tillage may far outweigh the benefits of C sequestration, unless N fertilizer application is delayed.
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