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Keywords:

  • nitrogen losses;
  • NO;
  • N2O;
  • land management

Abstract

[1] N fertilization significantly increases N2O and NO soil fluxes to the atmosphere. In spite of the expansion of agricultural activities in tropical managed soils from the developing world, there is little information about the loss of applied nitrogen (LAN) as NO and N2O from these areas. In this work, we determined LAN-N2O and LAN-NO from different crops during the growing season at a sandy soil experimental field and two active farms with loamy and clay soils, respectively. Tillage (T) and no-tillage (NT) farming were separately evaluated. All of the evaluated areas were located in the Venezuela savanna region. A large range of LAN-N2O (0.30–6.1%) and LAN-NO (0.26–2.1%) were recorded, with overall average values of 1.9% and 0.9%, respectively. LAN values were mainly affected by soil texture and rainfall pattern, which affected soil moisture and water-filled pore space. Also, soil management (T and NT) and the chemical composition of the N fertilizer played important roles. The overall average of LAN-N2O is about two times higher than the IPCC default value of 1%; therefore, our results suggest that a higher factor should be considered for cropping systems in tropical savanna regions.