Page 92 - Enzymes in Tropical Soils

80 Enzymes In Tropical Soils

arylsulphatase, decreased in the order of primary forest, secondary forest, and
cultivated land, in accordance with the decrease in soil total N (Table 5.10). Salam
et al. (1999e) also showed, from their study in soils with various lenghs of
cultivation in Central Lampung, Indonesia, that the total content of N in soils was
positively correlated with all investigated soil enzymes in the cassava fields (r =
0.545* - 0.934**), with the activities of acid and alkaline phosphatases in the
sugarcane fields (r = 0.455* and 0.837**, respectively), and with that of acid
phosphatase in the pineapple fields (r = 0.481*). Salam et al. (1998d) also
previously reported that the activities of some soil enzymes (acid phosphatase,
alkaline phosphatase,-glucosidase, and urease) were in general positively
correlated with the soil total N as depicted in Table 5.12. Similarly, Yusnaini et al.
(2007) also found good correlations between the soil total N and the activity of acid
phosphatase (r = 0.87**) and alkaline phospahate (r = 0.97**).

Table 5.12. The correlation coeffiecients between soil total N and
enzymatic activities.

Soil Enzymes Topsoils Subsoils

Acid Phosphatase 0.692* 0.711*
Alkaline Phosphatase 0.620 0.611
-Glucosidase 0.678* 0.516
Urease 0.721* 0.542
Adapted from Salam et al. (1998d)

Substitution of commercial fertilizers with organic fertilizers positively
affects some soil chemical properties important for plant gowth (Yusnaini et al.,
-1
2007). For example, the substitution of organic matter of 100% (20 ton ha )
improves the organic C, total N, and activities of some soil enzymes. Yusnaini et al.
(2007) also showed that the addition of chicken manure increased the organic C,
total N, and activities of soil enzymes more significantly than did the green manure
(Glyridium sp.). A linear relationship between activities of enzymes and total N
contents was also observed. This phenomenon is shown in Table 5.13. For
example, the addition of green manure 50 – 100% increased the soil phosphatase
-1 -1
activity from 39.8 to 42.0 – 47.6 mg p-Nitrophenol g h , while the addition of
chicken manure at the same level increased the activity to 189 – 239 mg p-

Abdul Kadir Salam - 2014