The pH and EC of the growing media

The pH and EC of the growing media were also be affected by different types of
fertilizers. Using organic fertilizers (vermicast and commercial bio-extract) increased the pH of
the soil medium compared to chemical fertilizer. These results suggested that vermicast and
commercial bio-extract could be a potential fertilizer to minimize the use of chemical fertilizer.
According to Maynard and Hochmuth (2007) [4], at a pH range of pH 5.5-6.8, Chinese kale is
able to grow normally, so the alkalinity of charcoal may not cause any detrimental effect on
Chinese kale growth because after mixing with soil, the pH of the soil medium was in a safe zone
for Chinese kale to growth.
Bulk density is an indicator of soil compaction and typically expressed in g/cm3
(USDA
Natural Resources Conservation Service, 2008) [19]. The ability of water and solute movement,
structural support and soil aeration were demonstrated via bulk density of the soil. Compacted
soil has a higher value of bulk density. Table 2 shows the effect of charcoal amendments and
fertilizers on the physical properties of growing media before transplanting and after harvesting.
Before transplanting, bulk density was increased by rice-husk charcoal and decreased by
rambutan charcoal compared with the control. Total porosity was increased by all growing media
before transplanting and after harvest. Air porosity before transplanting was increased by
Eucalyptus charcoal and decreased by rambutan charcoal and rice husk charcoal. In addition,
water holding capacity was increased by all soil treatments compared to the control before
transplanting and treatments had no effect after the harvest.
There was no significant difference in the height of Chinese kale at 1WAT and 2 WAT
when three different types of fertilizers were applied (Table 3). However, at 3 WAT, plant height
was influenced by types of fertilizer. Chemical fertilizer produced tallest plants (22.9 cm)
followed by vermicast (18.04 cm), while commercial bio-extract resulted in the shortest plants
(17.34 cm).
Plant height of Chinese kale was affected by type of charcoal (Table 3). At 1 WAT, plant
height was not influenced by any of the treatments compared to the control. However, plant
height was greater on plants growing on10:2 soil:rambutan medium compared to the 10:2
soil:rice husk medium. At 2 WAT, plant height was decreased by Eucalyptus charcoal compared
to the control and the remaining treatments which did not differ. At 3 WAT, plant height was
increased in plants grown with rambutan and rice husk charcoal. In addition, at 1 WAT, chemical fertilizer and Eucalyptus increased plant height compared to the control. The remaining
combinations of chemical fertilizer, vermicast or bio-extract with charcoal did not influence plant
height. At 2 WAT, all combinations of chemical fertilizer, vermicast, and bio-extract with
charcoal did not influence plant height. At 3 WAT, only chemical fertilizer plus rambutan
charcoal increased plant height compared to the control.
The growth of Chinese kale can be stunted in the condition of nitrogen shortage (Jones,
1998) [7]. The amount of macronutrients and micronutrients in the organic fertilizers was low
and not enough for plant to grow, so that using only organic fertilizers did not promote plant
growth (Pathanapibul, 2003) [14].