灰化紅黃壤平填系與磚紅化紅棕壤興化系土壤特性與成育之研究

Abstract

本研究目的為比較洪積母質所生成之灰化紅黃壤平鎮系，與由火山碎屑岩所生成之磚紅化紅棕壤興化系之剖面型態與理化特性，並檢討其成育與分類方法，結果摘錄如下： (一)平鎮系與興化系均具深厚之土層，除表土外層次不明顯，惟平鎮系之構造為強小角塊狀，構造壁平滑，土色鮮紅；興化系之構造體為中度小鈍角塊狀，構造面粗糙，土色偏黃紅，且全剖面具有肉眼不易覺察之小結核。 (二)二土系表層與底層之粘粒，差異甚明顯。平鎮系除表層外，其餘各層次之粘土或細粗粘粒比均甚高；但興化系之細粗粘粒比全剖面均無甚變化。土壤分散度與容積重，平鎮系較之興化系者為大，而燒失重則較小。 (三)鹽基置換能量與飽和度均甚低，全土壤與粘粒中各成分之組合雖有不同，惟無明顯之趨勢。平鎮系各層次之有機質量，C/N比值與粗坋砂所含可風化礦物等較之興化系者為小，全土壤之矽鋁或矽鐵鋁率，平鎮系之表層較之底層者高甚多，而興化系者則全剖面無甚變化。 (四)平鎮系與興化系之生成均遠自第四紀初期，且均分布於本省北部，自第四紀以來所受之氣候環境相似，但因二者母質不同，故成育之結果有異。平鎮系為具較多灰化特性之土壤，興化系則為磚紅化較明顯之土壤。 (五)從平鎮系與興化系土壤理化性質與成育關係之比較，灰化紅黃壤與磚紅化紅棕壤可以其剖面中之細粗粘粒與粗顆粒之成份作為診斷特性，依過去土壤分類方法，平鎮系歸屬於灰化紅黃壤，興化系歸屬於磚紅化紅棕壤，均尚適當，但若依第七草案之分類方法(1967)，平鎮系由於B層之有機質量低於1.5%，而粗坋砂中含可風化之礦物甚少，應歸屬於Paleudults大土類，興化系B層有機質超過1.5%者甚多，粗坋砂可風化礦物雖高，但未達到10%，故應歸屬於Palehumults大土類。 The purpose of this paper is to compare the soil properties of Ping-chen series, being classified as Red Yellow Podzolic Soil, and Hsing-hua series, a Reddish Brown Lateritic Soil, in order to find out some critical characteristics between these great soil groups. Soil morphologies and physico-chemical properties of four profiles, two of them representing Ping-chen series derived from diluvial deposit, and the others representing Hsing-hua series derived from pyroclastic fragments are studied. The results may be summerized as follows: Morphologically, both series are very deep in solum and with insignificant horizon differentiation under thin surface, Ping-chen series has strongly fine angularly blocky structure with smoth ped surfaces, and is red in color, while Hsing-hua series has moderately fine subangularly blocky structure with rough ped surfaces, and is yellow red in color, with some very fine iron concretions in the horizons. Data from physical measurement show that the movement of clay from surface soil to the subsoil is evident in both series. The ratios of fine clay to coarse clay in the subsoils are higher than those of the surface soils of Ping-chen series, but no marked difference was found in the Hsing-hua series. While the degree of dispersion and bulk density of Ping-chen series are higher than those of Hsing-hua series. By comparing the chemical data of the two series, exchangeable bases, cation exchange capacity, and base saturation are similarly low, and the variation of some element contents of whole soil or of clay fraction within series are larger than that between series. However, the ratio of silica to aluminum or silica to sesquioxide of whole soil is the highest in the surface soil of Ping-chen series, there is no significant difference of these ratios in the horizons of Hsing-hua series. Data of organic matter contents, C/N ratio, loss on ignition, and weatherable mineral content in coarse silt of Ping-chen series are lower than those in corresponding horizons of Hsing-hua series. These series are formed in similar climates, same period since quaternary and at locations short in distance within northern part of Taiwan. But the results are not the same due to the different parent materials. The characteristics of Ping-chen series show the tendency of podzolization, while those of Hsing-hua series represent the evidences of laterization. The relationship between soil characteristics and soil geneses are visible for Ping-chen series and Hsing-hua series. From which, the lowest ratio of fine clay to coarse clay in the surface soil and less contents of sesquioxide and bases in the coarse silt of sand in the genetic horizons may be considered as the critical characters between Red Yellow Podzolic Soils and Reddish Brown Lateritic Soils. If the soil classification of 7th Approximation is to be followed, the content of organic matter and weatherable minerals in the coarse silt and in the fine sane should be considered. Accordingly, two series similarly contain less than 10% of weatherable minerals in the argillic horizon, while Ping-chen series contains less than 1.5% of organic matter in the upper argillic horizon, but Hsing-hua series contains more than 1.5% of organic matter, so the former may be classified as Paleudults and the latter, as Palehumults.