| 摘要 | （一）本研究之土壤，選自桃園縣、中壢鎮、南勢附近，包括原爲紅棕壤之旱作茶園，與改作水稻田後，逐年按期作於收穫後採集之土壤樣本，歷經四年半，研究其剖面形態，分析各層代表土壤之理化性質計有機械組成、pH值、全鐵及游離鐵、二氧化錳、有效矽、磷及鉀、有機質、全氮量及陽離子交換性質等十一項。
（二）研究目的，在明瞭其土壤化育趨勢，以至水稻生成，研究結果詳列如表1-a, 1-b, 2-a, 2-b, 3-a及3-b，圖1-9。
（三）原紅棕壤旱田剖面之土壤，質地粘重，底土密實，滲透性緩慢，表土有機質少，四年半栽稻瀦水多仍保存原剖面之土壤底層之性態，僅改變表土與亞表土之顏色，自5YR轉爲7.5YR，非灌溉水之淋洗作用影響，而係土壤本身含鐵物質之水合作用之結果。
（四）根據化學分析結果，鐵、錳有移積於亞表土之趨向（見圖5, 6及7），惟土壤形態並無跡象，足見沉沉積尚輕，故土襄之淋洗層或沉積層均未形成，尚未能稱爲有稻田土壤化作用之呈現。
（五）土壤瀦水栽稻四年半，對於紅棕壤之最大影響，爲表土酸度之減退，pH值按年期逐漸上昇，自4.4-5.6，亞表土上昇較緩慢，底土影響至微。
（六）土壤潛水栽稻四年半，有增加表土磷、鉀有效性，與表土及亞表土矽之有效性之事實呈顯，對土壤有機質、全氮量與陽離子交換能量之影響甚輕微。
（七）就剖面形態，理化性分析結果，說明紅棕壤旱田改作水稻田，短期間內（4.5年），尚難有明顯之化育或成土作用可言，該類水稻土之生成，仍有待長期之影響與繼續之研究。 1. Nine soil profiles were collected from the reddish brown latosols of Nam-she, Chungli, Taoyuan, including the original tea plantation dry field, and its altered paddy field which were sampled after the first crop and the second crop each year from 1964-1968 respectively. Soil morphology of those profiles and their physico-chemical properties were studied. Items of this experiment consist of mechanical analysis, pH value, total iron free iron, manganese dioxide, available silica, available potash and phosphoric oxide, organic matter, total nitrogen and cation exchange capacity etc.
2. The purpose of this study is to want to know the trend of the development of reddish brown latosols which have altered to paddy field for 4.5 years and the genesis of the paddy soils. The results are showing on the Table 1-a, 1-b, 2-a, 2-b, 3-a, 3-b, and the Fig. 1-9 etc.
3. Soil characteristics of the original dry field of latosols are as follow, The soil texture is heavy, the consistancy of the sub-soil is campact and firm, the permeability is low, the organic matter content is low, it is still reserved the original properties of the subsoil after the rice cultivation and the flooding influence for 4.5 years. It was altered the color of surface and sub- surface soils only from 5YR to 7.5YR in color hue. It was not influence by elluviation from irrigated water but it was the results of hydration of iron compound of the soil body.
4. Base from the chemical analysis, there is a trend of some iron and manganese which illuviated on the subsoils but there is not any trace on the soil morphology so the illuviation of those soils are still very weak, no-elluvial and illuvial horizon are formed. In other word, there is not any appearance of paddy soil forming process.
5. The most great effect which influence to the reddish brown latosols by flooding rice plantation for 4.5 years was the decrease of soil acidity of the surface soil, the pH value increase from 4.4 to 5.6. The increase of sub-soil is less than that of the surface soil.
6. The availability of the phosphorous and the potash of the surface soils has increased after flooding rice plantation for 4.5 years, and so do the available silica of surface and subsurface soils, but there is a little effect on the soil organic matter, total nitrogen and cation exchange capacity.
7. Base on the results o soil morphology, physico-chemical properties, it is hard to formed apparent soil development of latosols after dry land which was altered to paddy field for a short time (4.5 years). So the genesis of the paddy soils which developed from latosols is still needed to weathered for a long time and we have to continue its study in the future. |
