The emission of nitrous oxide to the atmosphere was measured for 2 years (1977-79) from two clay soils (Denchworth and Lawford series) that had either been directdrilled or ploughed. On almost all sampling occasions the emission from directdrilled plots exceeded that from the ploughed plots by factors ranging up to 15-fold. Rates of nitrous oxide loss reached peaks of 2.5-3.0 mg N m-2 h-1 (equivalent to 0.6-0.7 kg N ha-1 day-1) from the direct-drilled plots on the Denchworth soil. Emissions of nitrous oxide from the Lawford soil were only 10-20% of those from the Denchworth soil. The total amount of nitrous oxide-N lost during each year from the Denchworth soil was estimated to be 5.4-8.6 kg N ha-1 from the direct-drilled plots and 0.9-5.6 kg N ha-1 from the ploughed plots.