Page 93 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 81

-1
-1
Nitrophenol g h , about 4 – 5 times higher. This pattern was also observed for
the increase in soil Organic C and Total N.
Addition of Urea, however, may decrease the activity of acid phosphatase as
shown by Table 5.11. The decrease is in relation to the decrease in soil pH by Urea
addition. As previously stated, the addition of urea may cause a significant
decrease in soil pH (Boulman et al., 1995; Salam et al., 1998c). This phenomenon
shows the more important role of soil pH in controlling the soil acid phosphatase
activity.

Table 5.13. The changes in soil properties as a result of substitution of commercial
fertilizers with organic fertilizer *.

Total
Org. C Av.P. Alk. Phos. -Gluk.
No. Treatment pH N
-1
-1 -1
mg kg mg p-Nitrophenol g h
1 Control 4.63 10.2 1.2 15.4 50.9 189
Org. Fertilizer
2 4.37 13.2 1.2 64.7 39.8 228
0%
Green Manure
3 4.60 12.4 1.3 49.1 42.0 230
50%
Green Manure
4 4.59 12.1 1.3 38.6 46.5 231
75%

Green Manure
5 4.79 12.6 1.3 27.0 47.6 234
100%
Chicken Manure
6 6.33 16.3 1.6 228 189 164
50%
Chicken Manure
7 6.37 15.0 1.7 270 218 331
75%
Chicken Manure
8 6.61 19.5 1.9 300 239 225
100%

*Adapted from Yusnaini et al. (2007); measurement was conducted after corn harvest

Abdul Kadir Salam - 2014