The sinkage and penetration resistances were measured after
puddling and after harvesting for the second rice in 2011 by using a
penetrometer (SC-900, Spectrum Technologies, Inc.) as described in
Kirchhof et al. (2000). The tensile strength was measured by using
soil cores sampled after three drainages during the rice growth
period. The penetrometer was equipped with a metal plate
(30402.80 mm) for measuring sinkage resistance and with a
cone (12.83 mm in diameter) for measuring penetration resistance.
The penetrometer was connected with an automatic recording
system to record and store the data of resistance force with depth.