台灣主要耕地土壤之鉀釋出特性之研究

Studies on the Desorption Characteristics of Potassium in Main Agricultural Soils of Taiwan

陳仁炫(Jen-Hshuan Chen) ； 洪建民(Jian-Min Hong)

《土壤與環境》 2卷3期 (1999/09) Pp. 235-249

https://doi.org/10.30058/SE.199909.0005

摘要

鉀在土壤中係屬動態（dynamic）平衡，不同型態鉀間之消長將主宰鉀在土壤中之有效性。除了速效性的溶液鉀和交換性鉀外，非交換性鉀在作物鉀吸收的供應上扮演重要角色。本文之目的即在探討本省主要耕地土壤之鉀釋出特性。本試驗選用台灣主要八種耕地之土壤（洪積母質紅壤、紅壤母質沖積土、砂頁岩黃壤、黏板岩非石灰性沖積土、黏板岩石灰性老沖積土、砂頁岩非石灰性新沖積土、砂頁岩石灰性新沖積土、和台灣黏土）。將已去除易利用態鉀之各種土壤分別加入0.001 M HCl溶液中，並添加H-飽和之陽離子交換樹脂（Bio-Rad AG.50W-X8），於25˚C下震盪0.5小時～40天，將土壤及樹脂分離後，以1 M NH4Cl溶液淋洗樹脂，測定不同時間所釋出之鉀量，該量即代表土壤非交換性鉀的釋出量，將非交換性鉀釋出量與時間作圖，即可得知每種土壤之非交換性鉀釋出曲線。藉此可瞭解不同供試土壤間之鉀釋出特性之差異，並探討鉀釋出特性與土壤性質間之關係，本試驗同時評估常用之五種脫附動力模式（零次、一次、拋物線、Elovich及modified Elovich方程式）在描述上述八種耕地土壤之鉀釋出特性的適宜性。藉由土壤非交換性鉀之最大釋出量和土壤性質之相關性分析得知，本省主要耕地土壤之非交換性鉀最大釋出量以石灰性沖積土大於非石灰性沖積土及其他強風化之土壤，而黏土礦物的種類與其含量以及土壤pH是造成非交換性鉀最大釋出量差異的主要因子。試驗結果亦顯示，拋物線擴散方程式（R^2=0.94**～0.99**）及一次方程式（R^2=0.90**～0.99**）較適合描述本省主要耕地土壤之非交換性鉀釋出特性，其中又以拋物線擴散方程式較佳。藉由鉀釋出的動力反應，可知擴散作用為控制土壤非交換性鉀釋出的主要機制。

關鍵字

鉀脫附 ； 非交換性鉀 ； 脫附動力模式

並列摘要

Potassium (K) is in a dynamic equilibrium in soil. The relative changes of different K forms are supposed to affect the K availability in soils. Besides readily available K (solution K and exchangeable K), nonexchangeable K play an important role in supplying K for plant uptake. The purpose of this study was to investigate the release characteristics of K of main agricultural soils in Taiwan.Soil samples were taken from eight main agricultural soils in Taiwan Diluvium Red Soils, Laterite Alluvial Soils, Sand Stone-shale Yellow Soils, Slate Noncalcareous Alluvial Soils, Slate Calcareous Older Alluvial Soils, Sand Stone-shale Noncalcareous Alluvial Soils, Sand Stone-shale calcareous Alluvial Soils, and Taiwan Clays). Soils those readily available K had been removed were added with moist Bio-Rad AG. 50W-X8 H- saturated resin into 0.001 N HCI solution. The samples were shaken at 25˚C for 0.5 hour to 40 days. After shaking, the resin was separated from the soil and then leached with 1 M NH4Cl solution. The amount of K was measured at different shaking times, which represented the concentration of nonexchangeable K released from the soil. The nonexchangeable K release curve was obtained from the plot of the amount of released K with time. The differences in the K release characteristics of the soils were evaluated with the curves, and the correlations between K release characteristics and soil properties also were determined. Meanwhile, the suitabilities of five desorption kinetic models (zero-order, first-order, parabolic, Elovich, modified Elovich equation) were evaluated to described the K release characteristics of the soils used in this experiment.The results showed that calcareous alluvial soils had higher maximum release of nonexchangeable K than those of noncalcareous alluvial soils and other strongly weathered soils. Based on the relationships between maximum release of nonexchangeable K and soil properties, it was concluded that the maximum release of nonexchangeable K of soils was largely governed by the kinds and the contents of clay minerals and soil pH. Results also showed that parabolic (R^2=0.94**~0.99**) and first-order (R^2=0.90**~0.99**) equations are more suitable to describe release characteristics of nonexchangeable K of main agricultural soils in Taiwan, and the parabolic equation is found to be the most suitable. Based on the release kinetic reaction of K, it was concluded that diffusion was the main mechanism to control the release of soil nonexchangeable K.

並列關鍵字

K desorption ； nonexchangeable K ； desorption kinetics models