Plant and Soil

, Volume 199, Issue 2, pp 239-250

First online:

Denitrification and total N losses from an irrigated sandy-clay loam under maize–wheat cropping system

  • T. MahmoodAffiliated withSoil Biology Division, Nuclear Institute for Agriculture and Biology
  • , K.A. MalikAffiliated withNational Institute for Biotechnology and Genetic Engineering
  • , S.R.A. ShamsiAffiliated withDepartment of Botany, University of the Punjab
  • , M.I. SajjadAffiliated withPakistan Institute of Nuclear Science and Technology

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Denitrification and total N losses were quantified from an irrigated field cropped to maize and wheat, each receiving urea at 100 kg N ha-1. During the maize growing season (60 days), the denitrification loss measured directly by acetylene inhibition-soil cover method amounted 2.72 kg N ha-1 whereas total N loss measured by 15N balance was 39 kg ha-1. Most (87%) of the denitrification loss under maize occurred during the first two irrigation cycles. During the wheat growing season (150 days), the denitrification loss directly measured by acetylene inhibition-soil cover and acetylene inhibition-soil core methods was 1.14 and 3.39 kg N ha-1, respectively in contrast to 33 kg N ha-1 loss measured by 15N balance. Most (70-88%) of the denitrification loss under wheat occurred during the first three irrigation cycles. Soil moisture and NO 3 - -N were the major factors limiting denitrification under both crops. Higher N losses measured by 15N balance than C2H2 inhibition method were perhaps due to underestimation of denitrification by C2H2 inhibition method and losses other than denitrification, most probably NH3 volatilization.

acetylene inhibition denitrification irrigated field maize 15N balance wheat