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The Chemistry and Fertility of Soils under Tropical Weeds 63

Cepeda and Gil-Sotres, 1987; Bonmati et al., 1991; Tate III et al., 1991; Martens et
al., 1992; Salam, 1996; Deng and Tabatabai, 1996; Salam et al., 1998b; 1999a;
1999b; Brzostek et al., 2013).
For example, it is reported that planting soils of a coffee plantation with
Paspalum conjugatum or natural vegetation (mixed vegetation of Chromolaena
odorata, Clibadium surinamense, Cludemia hirtam, Imperata cylindrica, Melastoma
affine, Mikania micrantha, and P. conjugatum) significantly increased the soil
organic C and total N content after 3 years. The increase in soil organic C and total
N accordingly increased the soil enzymatic activities as shown in Table 4.5 (Salam,
1996; Salam et al., 2001). Salam et al. (1999a; 1999b) state that the activity of
phosphatase increased in correlation with the increase in soil organic C and total N
contents. Reported by Brzostek et al. (2013) that the exudation of C by tree roots
also stimulated the microbial activity and the production of extracellular enzymes
in the rhizosphere.

Table 4.5. The effects of vegetation on some soil enzymatic activities of coffee
plantations in West Lampung Indonesia* (After Salam, 2014).

Ac. Phosp. Alk. Phosp. -Gluc. Arylsulf.
Soil Layer
1997 1999 1997 1999 1997 1999 1997 1999

A. No Vegetation (Control)
Topsoil 123 107 36 44 123 67 458 48

Subsoil 73 109 19 24 76 67 206 72

B. Grass (Paspalum conjugatum)
Topsoil 322 145 104 45 157 117 97 149

Subsoil 281 126 74 30 100 63 21 157

C. Natural Vegetation
Topsoil 271 156 36 54 168 129 165 143

Subsoil 284 122 27 26 191 60 139 148

-1 -1
*Adapted from Salam et al. (2001); ing p-Nitrophenol g h
Abdul Kadir Salam and Nanik Sriyani – 2019