本省柑橘園土壤之酸性化與其酸性來源
Other Title
Acid Source and Its Acidification of Citrus Orchard Soils of Taiwan
Journal
中華農業研究
Journal Volume
32
Journal Issue
1
Pages
83-91
Date Issued
1983-03-09
Date
1983-03-09
Author(s)
黃文良
Wen-Lian Huang
Abstract
本省之柑橘園，經過長時問的裸露式耕耘與連年施用生理酸性肥料，其土壤之酸性化已到相當嚴重的程度。樹齡超過10 年以上的柑桔園，除部分來自含石灰質較多母質者以外，多已示pH 4.2 至4.9 的強酸性反應，甚而有pH 4 以下的極端酸性者。在已示強酸性反應的柑橘園中，明顯的土壤特性為鹽基類的缺乏與交換性鋁的顯著增加。鋁離子飽和度，視石灰施用情形而異，但多已達40%至77%。鋁離子已取代鹽基而成為主要的交換性陽離子。在酸性構成要因中，與土壤pH 最有關連者，乃為置換酸度中佔79%至86%的三價鋁離子，在兩者間介有極顯著的負相關關係（r =-0.81 * * ）。在置換酸度中，其餘14%至21%為交換性氫。由於土壤中累積有相當量的水溶性SO4-及NO3-有可能生成游離酸。交換性鐵，在柑園土壤中，僅有微量存在，不構成為酸性來源。由此可知，本省柑橘園土壤的主要酸性來源為鋁離子〔Al( H2O ) 6 〕3+，經年累積結果，使得大多數柑橘園的土壤反應已降至pH 4.2 至5.2 ，即鋁離子的緩衝能範圍，並依鋁離子及鹽基性鋁離子含量的多寡，顯示其pH 值。
Most of citrus orchard soils of Taiwan are characterized by its strong acid reaction. The strong acidity of soils is presumed partially responsible for the low productivity and short life of citrus trees. Eleven citrus orchards which were representatives of the major citrus producing areas were selected and they have been cultivated for more than 12 years. Soil samples taken from these orchards were examined for acid substances and their acidification. The soil pH readings of most of these orchards ranged from 4.3 to 4.9, showing very strong acid reaction. Tong-shieh orchard soil which has been cultivated for 47 years showed a pH reading of 3.7, which is extremely acid. The cultivation method which remains the ground uncovered and long continuous application of chemical fertilizers containing acid substances have resulted in the rapid leaching out of soil bases and the accumulation of aluminum ions. The saturation degrees Of excha-ngeable aluminum in these orchard soils reached 40 to 77 per cent. Exchangeable aluminum content has a highly negative correlation with pH values (r = -0.81**). The existence of a measurable amount of hydrogen ions in the exchange acidity indicates its importance in soil acidity. The titration curves of N-KCl extractant also showed a strong buffer action of aluminum ions between pH 4.2 and 5.2. The lower the pH, the stronger was the buffer action of the extractants. It is suggested that acid source of citrus orchard soils of Taiwan mainly results from the accumulation of aluminum ion and hydroxyl aluminiumions which produces hydrogen ion on hydrolysis. When the cumulative amount of aluminum ions reaches certain level as a result of long-term cultivation, they may exhibit strong acid reaction with pH readings between 4.2 and 5.2, which is the buffer action range of aluminum ion.
Publisher
農業試驗所
Type
journal article
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