Comparison of 15N-depleted and 15N-enriched fertilizers as tracers

Abstract ( 14 NH 4 ) 2 SO 4 from which virtually all 15 N had been removed was compared as a tracer with (NH 4 ) 2 SO 4 containing 8.95% 15 N excess in a plant uptake experiment using soil columns maintained at ⅓ bar tension and conventional greenhouse pots. Uptake of fertilizer nitrogen in three cuttings of ryegrass ( Lolium Perenne L.) was identical with the two fertilizers. Estimates of residual fertilizer N in the pots agreed less closely, owing to the high dilution factor.