Fig. 6. Mineral N content in soil, simulated for different scenarios aimed to satisfy the demand for N by a reference wheat crop (Kafkafi and Halevy, 1974). Symbols indicate the N uptake by the reference wheat crop: Line 1, continuous N uptake; Line 2, simulated mineral N in sandy soil following 17 and 20 kg m^–2 sewage sludge compost (SSC) and cattle manure compost (CMC) applications, respectively; Line 3, simulated mineral N in agricultural soil following application of 6 kg m^–2 of SSC with 12 g N m^–2 or 6 kg m^–2 of CMC with 13 g N m^–2; Line 4, simulated mineral N in depleted sandy soil following application of 6 kg m^–2 of SSC with 20 g N m^–2 or 6 kg m^–2 of CMC with 23 g N m^–2. Arrows on the x axis indicate timing of mineral N applications on Days 14 and 35.