Fig. 3. Nitrogen uptake by wheat (shoots measured and roots calculated) and mineral N concentrations measured in soil through the third year of wheat grown in soil after three successive years of application of sewage sludge compost (SSC) (a, b, c) and cattle manure compost (CMC) (d, e, f) at three rates (3, 6, and 12 kg m^–2 yr^–1), versus simulated mineral N concentrations and net N mineralization in soil–compost mixtures. The concentration of mineral N was measured as mg kg^–1 and converted to g m^–2. Each point represents the mean of four replicates and the bars represent the SE.