Shallow depth placement of (NH4)2SO4 in submerged rice soils as related to gaseous losses of fertilizer nitrogen and fertilizer efficiency

Summary When nitrogen fertilizers are applied to rice, growing under submerged conditions, substantial gaseous losses of fertilizer nitrogen have been observed.Placement of the fertilizer at shallow depth greatly reduces these losses. A balance experiment using six different rice soils was carried out in a greenhouse. N¹⁵-labelled (NH₄)₂SO₄ (atom excess of 10% N-15) was applied on the surface and at 7 cm depth. Analysis of soil, roots and shoots showed that the difference in utilization of fertiliser nitrogen for surface and depth placement in pots could be accounted for by the difference in gaseous loss of fertilizer-N.