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Fig. 2. The relationship between the amount of N extracted as the mobile humic acid fraction (MHA) or calcium humates (CaHA) versus (a) soil organic C and (b) total soil N for the 0- to 15-cm depth of 14 tropical lowland rice soils. The mean coefficient of variation across the 14 soils in the amount of extracted N contained in the MHA and CaHA fractions was 4% for the three field replicates of each soil. For soil organic C and for total soil N the mean coefficient of variation was 1% for three laboratory replicates of a composite soil.
