|Morphological and physico-chemical studies on the representative profiles of Shin-pu series and Tsao-chiao series were carried out. The results may be citied as follows:
These two soil series have been derived from softy sandstone and shale of Tokazan formation of Pliocene-Pleistocene on rolling hills of Northern Taiwan and were formerly classified as Yellowish Brown Lateritic Soils.
Shin-pu series comprises sandy loam topsoil and clay loam bottom soil, it is yellowish brown in color with white and strong brown patches in the lower part of the profile, while Tsao-chiao series comprises sandy loam topsoil and sandy clay loam bottom soil and it is strong brown in color with big yellowish red patches in the lower part of the profile. In other words, Tsao-chiao soil is lighter in texture and is redder than Shin-pu soil. Besides these characters, both of them are quite similar morphologically and physico-chemically. Moderately deep sola of them do not show significant differential horizons. They have low organic content, low exchangeable bases and base exchange capacity, and weakly blocky structures.
In judging the clay content of A horizon being significantly lower than that of B, but no significant difference of clay content being found between B and C horizons, and the absence of clay skin in the profiles; amounts of clay have been leached out of the topsoils of both series without singificant deposition in the lower part of the profiles.
Concerning soil formation, total composition shows that sesquioxides are gradually increased with depth, while the distribution of silica is reverse, and the composition of clay fraction reveals a slight movement of sesquioxides down to B21 or B22 horizons. A similar trend of free iron movement is observed too, even though their content is rather low. In addition, fine clay content of B horizons is higher than any other horizons. These facts mean that Shin-pu and Tsao-chiao soils have heen subjected to processing of mechanical leaching and slight podzolization without the formation of texture B horizon.
About the degree of weathering, the presence of large amounts of weatherable minerals in fine sand and silt fractions with little horizon differentiation in the profile and the β values being higher than those of Podzols indicate the very low degree of weathering of these soil series and they are still remained in the young stage of podzolization.
In referring to the above statements and according to the suggestion of S.A.HARRIS Shin-pu and Tsao-chiao series may be classified as Sol Brun Acides, but if the 7th approximation will be followed, they shall be put in the catalog of Ruptic Alfic Dystrochrept because these soils contain ochric epipedon and cambic horizon with more than 35% of base saturation, and other characteristics mentioned above.