臺灣黑色土之研究Ⅰ　東臺灣黑色土之理化性狀

Studies on Black Colour Soils in Taiwan Ⅰ The Physico-Chemical Properties of Black Colour Soil in East Taiwan

朱惠民(H. M. Chu)

《中華農業研究》 11卷4期 (1962/12) Pp. 11-26

https://doi.org/10.29951/JARC.196212.0002

摘要

東臺灣黑色土分佈於海岸山脈之低丘陵至緩斜地帶，成小片狀與他類土壤間什存在，母質屬安山質集塊岩與凝灰岩，氣候年平均溫度約22℃，雨量1,700~2.000公厘，本研究冀自土壤理化性與相關因子以探索其成因。
土壤剖面性熊爲深或淺層晤灰棕至極暗灰棕之黑色土顛直接覆蓋於母質之上，質地屬鈷壤類，構造良好，多成細至中之鈍角塊狀或團粒狀，結構濕時粘而帶塑性，乾時甚硬，呈深而澗之裂隙，中酸至微鹹吐反應，中至緩透陸，有機質尚豐。研究剖面有四：其一由凝灰岩母質所形成，未經墾耕，餘爲安山岩質集塊岩所形成，均已被開墾，早作利用者分尚深與夔二剖面，水田利用者爲深土層。
土壤物理陸尚良好，水份當量頗高，此與粘土性質及含量和鹽基飽和度有關；未經利用者分散度甚小，而經人工利用者則增高達三倍以上；假比重在1.2左右，真比重約2.7，凝灰岩形成之土壤較大，接近母質之土層亦較大；粘土含量在20~40%之間，以凝灰岩形成之土壤爲高。
化學分析結果，置換鹽基總量，置換能量與飽和度均高，置換性氫則甚少，耕作地之表土鹽基飽和度一般均較低，從水田利用之土壤尚能具高鹽基置換能量觀之，知此類土壤雖經長期浸水其枯土礦物仍無甚變異。
土壤有機質表土在3~6%之間，底土則低至1%，水田利用者有機質含量顯較低。
全量矽在凝灰岩及其土壞均顯較低於安山質集塊岩者，粘粒中之矽與全量矽含量差異甚大，但在各剖面中均無甚變動，惟水田利用老顯較高。全量鐵與鋁均較粘土成分老低，土壞與母質間無甚差異，但在各剖面中略有向下移積之趨向，水田利用者止於第三層。其餘化學成分僅鹽基與磷略有變異而已。
生成熱帶與亞熱帶之黑色土主由於母質含高量之鈣鎂鹽類與粘土成份，氣候因子不足使土壤中之鈣鎂離子迅速移去，有機質與鈣鎂離子及鹼性矽酸鹽結合成安定隱固之鹽類，因而使土壤呈其特殊之黑色，由於鈣粘土在酸性碳酸鈣溶液中團聚力量大，故使此土壤成爲良好之團粒或核粒構造。
從土壤與母質之(K2O+Na2O)/Al2O3。所得之β值，知東臺灣黑色土多屬發育尚幼稚之土壤，從土壤化學成份之流失量計算結果，知道各剖面之總流失量均甚少，而流失成份除磷，鈣、鉀與鈉外，其餘各化學成份之流失百分率均甚微，故本類土壤應爲未成熟之土壤。
在土壤分類方面，Grumusols僅能包括部分之熱帶與亞熱帶之黑色土，東臺灣黑色土即在美國最新土壤分類草案中亦難獲得其適當之分類位置。

並列摘要

Black colored soils derived from andesitic or tuffic agglomerates occur in patches in association with other soils on roiling land and gently sloping hillside of coastal mountain ranges of East Taiwan. They have been formed under 22℃ of average annual temperature and 1,700-2,000 mm. of annual precipitation.
With the intention of studying the formation and classification of these soils a research on soil chemistry, physics, morphology and forming factors has been carried out.
Soil profiles overlying parent rocks range from 20 to more than 100 cm. in depth and from dark grayish brown to very dark brown in color. They are mostly clay loam in texture, sticky and plastic when wet and hard and highly shrinkable when dry, moderately to slow permeable, moderately acid to slightly alkaline in reaction and high in organic content, and they posses strong fine- to medium-sized pads of structures which are granular or subangular blocky. Soils studied consist of four profiles, one derived from tuffic agglomerate being virgin and three developed from andesitic agglomerate being cultivated.
The desirable physical properties and high moisture equivalent of these soils are related to their clay content, characteristics of clay mineral and base saturation. Degree of dispersion of virgin soils is low but that of cultivated soil is three times higher than that of the former. Soil density is about 2.7 and apparent density around 1.2, the former is higher for soils derived from tuffrc agglomerate than for those derived from andesitic agglomerate and is also higher for horizon near parent material than for overlying horizons. Clay content ranges from 20 to 40 per cent and it is richer in soils developed from tuffic material than those from andesitic.
Chemically, total exchangeable base, exchange capacity and base saturation are all high, meanwhile exchangeable hydrogen is low. But base saturation of surface soil of cropped land is reduced. The maintenance of fair base exchange capacity of paddy soil indicates that clay mineral have not been visibly altered by water-logged condition for a long times.
Organic content of surface soil ranges from 3 to 6 per cent of subsoil is reduced to 1 per cent and that of paddy field is somewhat lower than that of other soils.
Total analyses indicate that silica content is higher in andesitic agglomerate than in tuffic agglomerate and soils follow the tendency of their parent materials. Both total and clay fraction analyses show that there is not visible variation of silica content through the profile but it is higher in paddy soil. In total analyses the content of Fe2O3 and Al2O3 of soils are similar to that of their parent rocks and soils derived from tuffic agglomerate are richer in these elements. Within soil profile data of Fe2O3. and Al2O3 from total and clay fraction analyses very irregularly but show a faint tendency- of increase with depth, whereas for paddy soil these two elements accumulate in third layer.
Results of physical and chemical analyses indicate a tendency of ascending of base and soluble salts and little differentiation of horizons in the profile except some evidence of gleization of paddy soils.
Black colored soils of tropical and subtropical regions are developed from parent material rich in calcium and magnesium salts and sources of clay minerals under a climate not able to remove off these bases before the formation of stable salts by the combination of organic matter and basic silicates which makes these soils black in color, meanwhile, calcium-clay coagulate in calcium bicarbonate solution which promote the formation of stable granules or subangular blocks.
By comparing leaching value β of black colored soils of East Taiwan are young. The per cent loss of soil components reveals that in the process of soil formation only calcium, potassium, sodium and phosphorous have been lost to some extent, while other components do not show evidence of loss. It also explain the immaturity of these soils.
Mophologically, black colored soils of tropical and subtropical regions are similar in most aspects one another but owing to the broad area of distribution and different environments of formation the differences among them are still evident.
Concerning soil classification a part of dark colored soils in Tropics and Subtropics may be classified as Grumusols while most of them can not be put in any group of suggested system of soil classification of U. S. A. in 1960, and Black color soils in East Taiwan can not either too.