Figure 4

Ca and Mg contents in soil as influenced by crop rotation (I), manure application (II) and mineral N rate (III) in the long-term field experiment at Grabow, Poland. Error bars denote standard deviations (n = 3). LSD(P ≤ 0.05): for Ca: I = 0.32, II = 0.43, III = 0.36, Interactions = not significant; for Mg: I = 2.11, II = 2.02, III = 1.25, Interactions = not significant.