Thkuapa Experimentat Site
Soil hardness measurement was conducted at every plot with different treafinents. Fig. 3
shows the pat0em of the soil hardness, which is quite similar at every point examined. This
was because the distribution of soil materials were quite uniform within the whole
experimental si!e, indicating that any trcatment could not be significant to modiS the soil
physical properties. The ODP value was more than 2.0 only at the surface 15 crn at most.
Below that depth, it ranges between O.4 &0.6, showing very sfiong resistance against the root
peneftation. This was confirmed to dig out the ftee and crops. Eucalyptus root suffered from
physical disturbance of gravelly materials. Table 2 showed the ratio of gravel (particles grcater
tharr 2 mm in diameter) to tlle total soil materials in two plots. TE-01 is confiol plot without
any treafinent and only mulching teatment was done NTE-02. At the surface 30 cm, gravel