The increased C supply (putative root mortality, litter fall, application of an organic amendment and the return of crop residues) in the Amng orchard will have provided substrate to support additional microbial growth which will have resulted in an associated rise in microbial respiration (Rastogi et al., 2002), thus explaining the significant (Tukey–Kramer test, P = 0.05) 20% rise in soil CO2 emissions.