Page 111 - Ilmu Tanah Book

98 The Chemistry and Fertility of Soils under Tropical Weeds

This pattern clearly shows the acceleration of nutrient cycles in the soil
environment after deforestation. A big part of C and N leaks out of the soil
-
environment in the form of CO 2 , NO 3 , and N 2 , which might finally cause the
decrease in microbial population and activities as indicated by the decrease in soil
enzymatic activities as shown in the previous sections. In addition, the sources of C
and N also decrease caused by the changes in the dominant vegetation. A similar
pattern is also shown by P (Fig. 6.4).

Table 6.5. The effect of land-use conversion on soil organic C and total N
contents in Bukit Ringgis West Lampung Indonesia*
(After Salam, 2014).

Soil Depth Organic C Total N

-1 -1
(cm) (g kg ) (g kg )

0 – 20 60.4 5.5
Primary Forest
20 – 40 25.0 2.3
0 – 20 41.4 3.4
Secondary Forest
20 – 40 21.7 2.0

0 – 20 28.5 2.3
Coffee Plantation
20 – 40 10.1 1.2

0 – 20 15.8 1.7
Cultivated Land
20 – 40 7.5 0.8

*Adapted from Salam et al. (1998b)

6.3 Effects of Weed Management

Soil organic C or organic matter content, Available P, Total N, and S are
controlled by several factors, among which are types of land-uses, types of
vegetation, and soil tillage system. The organic matter contents, organic C, Total N,

Abdul Kadir Salam and Nanik Sriyani – 2019