(25(4):273-280)STUDY ON THE AVAILABLE SILICA AND THE PHYSICO-CHEMICAL PROPERTIES OF THE SOILS OF PADDY FIELD IN TAIWAN

1. 研究之土壤樣本共413個，選自全省各地。分析項目共七項，其目的在尋求水稻田土壤之有效矽與其他理化性之相關，以說明其應用問題。 2. 本省水稻土壤種類及其有效矽之含量見表一，沖積土之表土有效矽之平均值自7.1~29.8mg/100g，以安山岩質沖積土含量較豐，泥岩質者次之，粕板岩質者再次之，砂岩頁岩質者更次之，片岩質者較低，105個表土之總平均值為13.3mg/100g。 3. 水稻田土壤之質地與有效矽含量之關係見表二，不論沖積土與紅黃壤之水田，除壤質砂土外，其各種質地土壤均以粕重者其有效矽含量亦高，反之，輕鬆者則相對減低。 4. 水稻田土壤之有機質與有效矽含量之關係見表三，表土有機質多在1~3％內， 其含量之高低隨有效矽成正相關關係，土壤之反應與土壤之有效矽亦呈正相關關係，見圖一。 5. 應用統計方法，求出各種土壤或各地區土壤之有效矽與其他化學性質之劃目關，及其迥歸係數見表四及表五，就中以PH值之正相關最顯著，CEC之負相關則不顯著。 6. 本省水稻田土壤之有效矽含量，多在中等以上，其在10mg/1009以下者僅占分析總數1/10，在4mg/100g以下者占1/80。 1. 413 soil samples were selected from various location of whole province. 7 items of physico-chemical properties were analyzed. The purpose of this study was to understand the correlation between the available silica and other physico-chemical properties of the paddy soils in order to investigate the application of the available silica. 2. The available silica of the various paddy soils in Taiwan was shown in table 1. The average silica contents of the alluvial surface soils were from 7.1-29.8 mg/100g, showing the decending order of the follows: the andersite alluvial soils>the mudstone alluvial soils>the slate alluvial soils>the sandstone and shale alluvial soils>the schist alluvial soils. The grand average of the 105 surface soils was 13.3 mg/ 100g. 3. The relationship between the soil texture and the available silica of the paddy soils was shown in table 2. Except for loamy sand, high contents of available silica were associated with heavy texture, irrespective of alluvial soil or paddy latosols. 4. The relation of soil organic matter content and the available silica of paddy soils was shown in table 3. Most of the organic matter content of the surface soils were within the range of l-3%. It gave positive correlation between the content of the organic matter and the available silica. This was also true for the correlation between pH and the available silica. (see Fig. 1) 5. The multiple correlation and regression coefficient between the content of available silica and the other chemical properties were calculated, based on the different soil types and in different part of Taiwan. It was shown on table 4 and 5. The positive correlation of pH was highly significant and the negative correlation of CEC was insignificant. 6. Most of the available silica contents of the paddy soils in Taiwan were in the medium range, the content less than 10mg/100g occupied 1/10 of the whole samples and content less than 4 mg/100g occupied 1/80