Page 162 - Ilmu Tanah

The Chemistry and Fertility of Soils under Tropical Weeds 149

three soil properties with correlation coefficients ranging from 0.710 – 0.907, 0.767
– 0.883, and 0.754 – 0956, respectively.
The above data show that forest conversion lowered the availabilities of heavy
metal micronutrients due to several reasons. Forest clearing changed the soil
microclimate, particularly related to the soil moisture content and temperature
that might have accelerated the soil mineral weathering and organic matter
decomposition due to the increased microorganism population and activities.
Intensive soil tillage might have also accelerated this process and decreased the soil
organic matter content, that might have finally changed the availabilities of heavy
metal micronutrients. Soil erosion and leaching after land clearing might have also
accelerated the losses of these metals. Conversely, fertilization in coffee plantation
and cultivated land might have slightly increased the availabilities of Cu and Zn due
to the fertilizer contaminants. The phenomenon is shown by the slight increase in
the availabilities of Cu and Zn in the land system of Bukit Ringgis and Sekincau.

4

3.5
3
Avail. Cu (mg kg -1 ) 2.5

2

1.5
1

0.5
0
Primary Secondary Coffee Cultivated
Forest Forest Plantation Land

Topsoil Subsoil

Fig. 8.8. The changes in soil available Cu in different land-use systems of
Tri Mulya, West Lampung, Indonesia ((Redrawn from Salam, 1999).).

Abdul Kadir Salam and Nanik Sriyani – 2019