Evidence of N 2O emission and gaseous nitrogen losses through nitrification-denitrification induced by rice plants ( Oryza sativa L.)

A greenhouse experiment was conducted with a specially designed apparatus consisting of an upper and lower chamber where the treatment with rice was carried out (treatment 1). The apparatus also had a single chamber where treatment 2, without rice plants, was carried out. The scope of this study was to elucidate the influence of rice plant growth on gaseous N losses as N ₂ and N ₂O produced by nitrification-denitrification in a flooded soil fertilized with (NH ₄) ₂SO ₄ (with 56.50 atom% ¹⁵N). Gas samples were withdrawn weekly and analyzed for (N ₂ + N ₂O)- ¹⁵N losses by mass spectrometer and for N ₂O by gas chromatograph. The gaseous (N ₂ + N ₂O)- ¹⁵N losses of the treatment with rice plants were significantly ( P =0.01) higher than those of the treatment without rice plants, as were the amounts of N ₂O emitted. Rice plants facilitate the efflux of N ₂ and N ₂O from soil to atmosphere, as about half of the total gaseous ¹⁵N loss as N ₂ and N ₂O was found in the upper chamber. The proportion of N ₂O- ¹⁵N to (N ₂ + N ₂O)- ¹⁵N in the upper chamber was 10.56%, much higher than that of the lower chamber in treatment 1 and the headspace of treatment 2.