Soil Morphological, Mineralogical and Chemical Characteristics of Tea Gardens with High-Quality Leave Production in Thai Nguyen province, Vietnam

抄録

Tan Cuong commune in Thai Nguyen province is praised for the best tea quality among the northern region of Vietnam. In the commune, the market price of tea leaves was high at the gardens close to the Cong River and tended to lower with increasing distance from the river. In this context, soil morphological, mineralogical and chemical properties were investigated to characterize the soils in four tea gardens which were located on a transect line established perpendicularly to the river: TB1 close to the river, TB2 to TB4 away from the river and located on the previous dikes. The investigation was also conducted at two forested patches (FB1 and FB3) adjacent to TB1 and TB3. In addition, one garden was selected in Song Cau commune (TS1), located on a hillslope. All of the tea garden soils were strongly acidic throughout the profile with high contents of exchangeable Al. At the riverside, the TB1 and FB1 soils were classified as Typic Ustipsaments. They were sandy and predominated by quartz and kaolin minerals in the clay fraction. Meanwhile, the TB2 to TB4 and FB3 soils far from the river were Typic Dystrusteps while the TS1 soil was Typic Paleustults. These soils were relatively fine textured with various kinds of 2:1 clay minerals. The (Fe_d-Fe_o)/Fe_t ratio was the lowest in TB1 and FB1 and the highest in TS1. The analysis of total element contents agreed with the difference in these mineralogical properties. In addition, the influence of soil disturbance was found in TB2 and TB4. While the former was weakly reflected only by discontinuity of the horizon stratification and mineralogical properties, the latter was so severe resulting in a very shallow soil depth with abundant rock fragments.