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Fig. 1. The relationships between properties of humic acids (HA) extracted from predried soil versus fresh soil for the 0- to 15-cm depth of two fertilizer treatments at three sites of the Long-Term Fertility Experiment: (a) amount of N extracted as HA (HA-N), and (b) C/N ratio of HA (HA-C/N). The mobile humic acid fraction is the MHA, and the calcium humate fraction is the CaHA. Each data point represents one field replicate of a fertilizer treatment at each site.
