Figure 1

Organic C and microbial biomass C 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 C org.: I = 0.52, II = 0.65, III = 0.23, Interactions = not significant; for microbial biomass C: I = 11.5, II = 10.1, III = 11.2, Interactions = not significant.