Field study of the fate of labelled fertilizer ammonium-N applied to sesame and sunflower in a sandy soil

The recovery in crop and soil of labelled fertilizer ammonium-N applied to sesame and sunflower growing on sandy soil was measured. The sesame and sunflower received respectively 238 and 143 kg Nha⁻¹ as (NH₄)₂SO₄ enriched with 4.63 At. %¹⁵N excess. In the plants, the Ndff was 31.19% and 31.96% in sesame and sunflower, respectively. The fertilizer recovery by sunflower was 22.3%, by sesame only 12.3%. The amount of fertilizer N remaining in the soil at harvest was 13.04% for the sesame and 5.95% for the sunflower plot. The loss of fertilizer N under sesame was 74.66% and 71.75% under sunflower. The average of seed yield of the plants inside the¹⁵N plot was compared with the seed yield of the same amount of plants from outside the¹⁵N plot. They did not differ significantly, indicating that the results obtained from the¹⁵N plot can be extrapolated to the rest of the field.