Page 117 - Ilmu Tanah

104 The Chemistry and Fertility of Soils under Tropical Weeds

the activities of soil enzymes will be measured in the soil system (Fig. 6.6). Direct
relationship between the activities of some soil enzymes and soil organic C or
organic matter contents has been reported (Nannipieri et al., 1980; Harrison, 1983;
Trasar-Cepeda and Gil-Sotres, 1987; Bonmati et al., 1991; Tate III et al., 1991;
Martens et al., 1992; Salam, 1996; Salam et al., 1998b). As previously mentioned,
Salam et al. (1998b) report that the activities of acid phosphatase, alkaline
phosphatase, urease, and arylsulfatase in several land-use systems decreased in
the order of primary forest, secondary forest, and agriculture lands, in a
accordance with the decrease in the contents of organic matter in the respective
land-uses. Tate III et al. (1991) also report that the activities of soil microorganisms
and phosphatases in soil Horizon O rich in organic matter were 2 – 25 times higher
than those in soil Horizon A with low content of organic matter. The enzymatic
activities involved in the cycles of C, N, P, and S in the soil – plant systems in soil
enriched with organic matter were shown to significantly higher than those in the
control soils (Martens et al., 1992). This relationship is related to the roles of
organic matters as energy sources for microorganisms producing soil enzymes.

Table 6.9. Changes in soil organic C and total N in hilly coffee plantation under different
vegetation* (After Salam, 2014).

-1
-1
Organic C (g kg ) Total N (g kg )
Control NV PG Control NV PG

1996 22.3 28.8 34.7 1.7 2.2 2.7

1997 14.7 17.1 29.1 1.3 1.3 2.3

1998 16.4 18.9 28.9 1.1 1.8 1.1

1999 21.1 23.0 50.0 1.8 2.1 2.4
*Adapted from Salam et al. (2001); NV = Natural Vegetation, PG = Paspalum conjugatum

Abdul Kadir Salam and Nanik Sriyani – 2019