the effect of elevated co2 and n on decomposition of wheat straw and alfalfa residues in calcareous and non calcareous soils

incorporation of plant residue in soils is considered as an important agricultural practice for maintaining soil fertility in sustainable agricultural system. co2 levels, nitrogen fertilization and plant residues are factors which highly affect decomposition of added organic matter to soil. in this research controlled chambers were used to investigate the effects of elevated atmospheric co2 concentrations (350 vs. 760 co2 ppm) under two n fertilization levels (0 vs. 500 kg n ha-1) and two replicates on decomposition of wheat and alfalfa residues in two calcareous (32.66 % caco3) and non calcareous soils (3.4 % caco3) at 6 times (0, 10, 20, 40, 60 and 90) under laboratory condition. soil moistures were adjusted at 70% of field capacity. the results showed that elevated co2 significantly increased decomposition of residues in both calcareous and non calcareous soils. in the samples that received n fertilizer, decomposition of wheat straw and alfalfa residues increased in both soils. from the obtained results, we concluded that in all treatments the amount of decomposition of wheat straw and alfalfa residues in calcareous soil were higher than non calcareous soils.