Page 115 - Ilmu Tanah

102 The Chemistry and Fertility of Soils under Tropical Weeds

conventional tillage in the cassava plantation. The pattern of the changes in soil
pH, organic C, Total N, and available P under continuous cropping was also
observed in sugarcane and pineapple plantation in Central Lampung (Table 6.7).
The pattern was not clear, probably due to the variation in crop management
related to soil treatment.

Table 6.7. Selected soil chemical properties of cassava, sugarcane, and pineapple
plantation of different time of cultivation*.

Years Organic C Total N Avail. P
Plant pH -1 -1 -1
Cultivated (g kg ) (g kg ) (mg kg )
Cassava SF Nearby 4.7 43.0 2.6 5.03
1 – 5 4.5 20.0 1.0 24.7
6 - 10 4.4 12.8 0.8 7.70

Sugarcane SF Nearby 5.1 22.9 0.8 8.44
3 5.2 18.6 0.8 7.19
9 4.9 28.3 1.6 8.16
13 5.5 14.6 0.7 23.1
20 4.7 23.1 0.9 63.6

Pineapple Just Opened 4.6 14.4 0.8 199
1 4.3 12.3 0.7 3.12
2 4.3 12.3 0.7 3.17
3 4.0 15.2 0.8 11.0
4 4.0 13.5 0.7 21.5

*Adapter from Salam (1999b); SF Secondary Forest

Salam (2014) suggests that the vegetation grown may be one reason for the
differences in organic C and organic matter contents (Chan, 1997; Studdert et
al.,1997; Salam et al., 2001). Some reports (Chan, 1997; Studdert et al., 1997) show
that soil planted with grasses contained organic matters higher than soils planted
with food plants. This observation indicates that grasses are potential to enhance
or restore the fertility of soils with degraded organic C and organic matters (Table
6.8). Studdert et al. (1997) also report that the rotation of food plants with grasses

Abdul Kadir Salam and Nanik Sriyani – 2019