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Enzymes in Tropical Soils 75

Table 5.8 Fractionation of fulvic and humic acids in soils treated with
some tillage systems*.

Tillage Total C Fulvic Acids Humic Acids

System ....... % .......
Intensive
1 1.80 15.56 142
Tillage

Minimum
2 1.86 27.60 66.42
Tillage
3 No Tillage 2.14 19.59 59.91
*Adapted from Sarno et al. (1998)

0
Soil Depth (cm) 30 Fulvic Acid

60
90
Humic Acid
120
0 0.5 1
-1
Organic C (g kg )

Fig. 5.5. Concentrations of fulvic and humic acids in soil
(Medonca and Rowell, 1996).

Table 5.9. The correlation coeficients between soil organic C and
enzymatic activities.

Soil Enzymes Topsoils Subsoils

Acid Phosphatase 0.716* 0.823*
Alkaline Phosphatase 0.584 0.716*
-Glucosidase 0.672* 0.404
Urease 0.734* 0.529

Adapted from Salam et al. (1998d)

Abdul Kadir Salam - 2014