Fig. 4. The effect of labeling the NH₄ pool in cattle slurry (CS) at 52 atom% ¹⁵N on the rate of dilution of the NO₃ pool in soil, enriched by the application of KNO₃ containing 52 atom% ¹⁵N at the same time to grassland on four occasions in 1997. (LSD values are for comparing any two means at P < 0.05).