Page 85 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 73

+
(2001), humic acids are also useful to buffer the soil solution H and thereby the
soil pH does not easily change due to acid or base additions.

Table 5.7. Changes in soil phosphatases and -glucosidase activities in soil planted with
long-term cassava in Central Lampung*.

Acid Alkalin -
Landuses Phosphatase Phosphatase Glucosidase
-1
mg p-NPP g h 
-1
Forest 250 85 61
Cassava
85 48 39
(1 year)
Cassava
71 39 36
(4 years)
Cassava
56 35 37
(10 years)
Corn 110 38 41
Long Bean 200 36 38
*Adapted from Salam et al. (1997c)

Extracted with
Treated with Treated with
No Treatment 0.1 - 0.5 M Alkali Acid
NaOH

Soluble Fractions
(Fulvic Acids)
Soluble Fractions
Humic Substances Insoluble Fractions
(Decomposed) (Humic Acids)
Soil Organic Insoluble Fractions
Matter Non Humic (Humin)
Substances)
(Undecomposed)

Fig. 5.4. Fractionation of humic substances in soil system (Salam, 2012).

Abdul Kadir Salam - 2014