부산대학교 도서관

The recovery of15N labelled ammonium fertilizer as well as biological N2fixation of fababean (Vicia faba minor) was studied in two cropping sequences: fababeansugar beet and spring wheat-fababean. With fababean as the first crop, 20 kg N ha-1labelled with 11.4%15N atom excess (a.e.) was applied. The fertilizer N recovery of the first crop of fababean was 15.8%. Whereas 82% of the N in the fababean was derived from the atmosphere through biological fixation, 16% came from soil and only 2% from fertilizer. The recovery of residual labelled fertilizer N by the subsequent sugarbeet crop was 3.9%. The total fertilizer N recovery over the two years was therefore about 20%. In the second cropping sequences, 50 kg N ha-1labelled with 11.3%15N a.e. was applied to spring wheat. The fertilizer N recovery of spring wheat was 36.0% in this sequence. 20% of the N in the spring wheat was derived from fertilizer and the remaining 80% from soil. 1.6% of the residual labelled fertilizer was recovered by the subsequent fababean crop. The total recovery of fertilizer N in the second sequence was therefore about 38%. The recovery by the first crop almost entirely determined the total N recovery over the two years cropping sequences.