Three years of nitrous oxide and nitric oxide emissions from silandic andosols cultivated with maize in Hokkaido, Japan

Abstract

We measured nitrous oxide (N2O) and nitric oxide (NO) emissions during the snow-free season (April–November) over a 3-year period (1998–2000) from a Silandic Andosols cultivated with maize (Zea mays L.) in central Hokkaido, Japan. In May, before furrowing, composted cattle manure was broadcast onto the field at a rate of 3.0 g N m−2. After furrowing, chemical fertilizer (NH4)2SO4-N + (NH4)3PO4-N : urea-N at a ratio of 10:3 was applied to the row at a rate of 13 g N m−2. An impermeable layer lay 1.3 m below ground level. As a result, after heavy rains and during the snow-melting period, the groundwater table rose to near the ground surface. The N2O and NO emission rates ranged from 0.0 to 6.4 and from 0.00 to 0.94 mg N m−2 h−1, respectively. The highest N2O emission was observed after heavy rain in summer and autumn. The magnitude and seasonal pattern of N2O emissions from the inter row were similar to those from the row itself, although chemical fertilizer had not been applied to the inter row. In contrast, an increase in NO emissions was observed only from the row. Seasonal fluctuations in soil NH− 4 and NH− 3 concentrations and the emission ratio N2O-N/NO-N suggested that N2O and NO emitted after fertilizer application (May to early July) were produced mainly by nitrification, whereas N2O emitted after heavy rains (after mid-July) was produced mainly by denitrification. Total N2O and NO emissions during the snow-free season ranged from 0.7 to 2.8 and from 0.0 to 0.7 g N m-2, respectively, over a 3-year period. The N2O and NO emissions from our field were relatively high compared with those reported worldwide. In contrast, reported N2O emission rates from agricultural Andosols in Japan are typically lower than those from other agricultural soils in Japan and around the world. Therefore, the results of the present study suggest that high N2O emissions may occur from Japanese agricultural Andosols that are poorly drained.