Details

Autor(en) / Beteiligte

• JOHN, P.S.
• BURESH, R.J.
• PRASAD, R.
• PANDEY, R.K.

Titel

Nitrogen gas (N2 + N2O) flux from urea applied to lowland rice as affected by green manure

Ist Teil von

• Plant and soil, 1989-09, Vol.119 (1), p.7-13

Ort / Verlag

Dordrecht: Kluwer Academic Publishers

Erscheinungsjahr

1989

Quelle

SpringerLINK Contemporary (Konsortium Baden-Württemberg)

Beschreibungen/Notizen

• A field study was conducted on a clay soil (Andaqueptic Haplaquoll) in the Philippines to directly measure the evolution of (N₂ + N₂O)-¹⁵N from 98 atom % ¹⁵N-labeled urea broadcast at 29 kg N ha⁻¹ into 0.05-m-deep floodwater at 15 days after transplanting (DT) rice. The flux of (N₂ + N₂O)-¹⁵N during the 19 days following urea application never exceeded 28 g N ha⁻¹ day⁻¹. The total recovery of (N₂ + N₂O)-¹⁵N evolved from the field was only 0.51% of the applied N, whereas total gaseous ¹⁵N loss estimated from unrecovered ¹⁵N in the ¹⁵N balance was 41% of the applied N. Floodwater (nitrate + nitrite)-N in the 5 days following urea application never exceeded 0.14 g N m⁻³ or 0.3% of the applied N. Prior cropping of cowpea [Vigna unguiculata (L.) Walp.] to flowering with subsequent incorporation of the green manure (dry matter = 2.5 Mg ha⁻¹, C/N = 15) at 15 days before rice transplanting had no effect on fate of urea applied to rice at 15 DT. The recovery of (N₂ + N₂O)-¹⁵N and total ¹⁵N loss during the 19 days following urea application were 0.46 and 40%, respectively. Direct recovery of evolved (N₂ + N₂O)-¹⁵N and total ¹⁵N loss from 27 kg applied nitrate-N ha⁻¹ were 20% and 53% during the same 19-day period. The failure of directly-recovered (N₂ + N₂O)-¹⁵N to match total ¹⁵N loss from added nitrate-¹⁵N might be due to entrapment of denitrification end products in soil or transport of gaseous end products to the atmosphere through rice plants. The rapid conversion of added nitrate-N to (N₂ + N₂O)-N, the apparently sufficient water soluble soil organic C for denitrification (101 µg C g⁻¹ in the top 0.15-m soil layer), and the low floodwater nitrate following urea application suggested that denitrification loss from urea was controlled by supply of nitrate rather than by availability of organic C.