三種分析方法在測定肥料中有機質含量之適宜性評估

Evaluation of the Suitability of Three Analysis Methods for Determining Organic Matter Contents in Fertilizers

陳仁炫(Jen-Hshuan Chen) ； 蔡蕙芳(Hui-Fang Tsai) ； 林毓雯(Yu-Wen Lin)

《臺灣農業化學與食品科學》 42卷2期 (2004/04) Pp. 116-124

https://doi.org/10.6578/TJACFS.2004.017

摘要

土壤有機質含量一般被視為土壤肥力的指標，且可藉此評估土壤生產力的高低。有機質肥料的適當施用是最直接且可顯著提高土壤有機質含量的方法。有機質肥料中有機質含量的測定方法甚多，惟各有其缺點而影響其正確性。本研究之目的在比較並評估三種有機質含量測定法（乾灰化法、濕氧化法和元素分析法）在測定不同種類的植物性、動物性和腐植酸類肥料的有機質或有機碳含量之適宜性，並比較三種方法之測值間的關係，以建立最適宜的有機質含量測定法。結果顯示，雖然乾灰化法的取樣量比濕氧化法和元素分析法多，且由於取樣不均所造成的試驗誤差相對較小，但本試驗以乾灰化法測定非有機質之碳酸鹽肥料時，亦可測得有機質含量 (LOI)，是故將乾灰化法所損失之重量視為有機質含量的作法並不十分正確。試驗結果亦顯示，若在濕氧化法之操作過程中，將液溫維持150℃，繼續加熱五分鐘所測得之可氧化有機碳 (OXC (heating)) 值與由元素分析法所得之全有機碳 (TOC) 測值極為相近，且可由OXC (heating) 值代入TOC=0.995 OXC (heating) +0.42(R^2=0.97(上标 **))方程式而估算有機質肥料之全有機碳量。本試驗結果亦顯示，植物類、動物類和腐植酸類有機質肥料的LOI/TOC及LOI/OXC(heating)比並非定值，故以傳統上將Walkey-Black濕氧化法測得之OXC或OXC (heating) 測值乘以定值來估算有機質含量的方式，並無法正確的反映有機質的實際含量。利用元素分析法雖可測得有機質肥料之全有機碳含量，但該法使用的樣品量極少，且因樣品均質性較差，因此，測值變異值較大，且必需有昂貴之元素分析儀的配置，故綜合本試驗的結果，目前國家標準 (CNS) 所使用的乾灰化法的測值，並不能反映實際有機質肥料的有機質含量，而加熱濕氧化法之OXC (heating) 測值與有機質肥料之全有機碳含量極為接近，故以有機碳含量作為有機質肥料之品目標準將比有機質含量有意義。

關鍵字

有機質含量 ； 幹灰化法 ； 濕氧化法 ； 元素分析法

並列摘要

The content of organic matter in soil can be regarded as an index of soil fertility and also can be used to evaluate the productivity of soil. Therefore, organic fertilizer addition is the most direct and useful practice for increasing soil organic matter content. Several methods have been used to measure the contents of organic matter in organic fertilizers, but all of them have disadvantages in terms of measurement. The objectives of this study were to compare and evaluate the suitability of three commonly used methods (the dry ash method, wet oxidation method, and elemental analysis method) for determining the contents of organic matter or organic carbon in organic fertilizers, and for developing the most suitable analysis method. Results showed that although the variance of measurement was less for the dry ash method than for the other two methods due to its larger sample size, the LOI values were also dertermined from fertilizers containing carbonate. Therefore, the assumed loss of weight in organic fertilizers as the dry ash method was used to measure the organic matter content was no correct. Results also showed that the OXC (heating) values, which were determined as the liquid temperature was kept at 150℃ for five minutes, were close to the values of TOC obtained using the elemental analysis method. Therefore, the OXC (heating) values could be converted into TOC values using the equation TOC=0.995 OXC (heating) +0.42(R^2=0.97(superscript **)). No constant values of LOI/TOC or LOI/OXC (heating) were found for plant-type, animal-type, or humic acidtype organic fertilizers, so it was critical for common mean that using the values of OXC or OXC (heating) time a constant value to get the contents of organic matter in organic fertilizers. Although the TOC content could be determined using the elemental analysis method, the variance of measurement tended to be higher because of the sample size is small as well as samples usually are heterogeneous, and expensive equipment was needed in this method. It was concluded that the LOI value measured using the dry ash method, which is suggesded to be the official method by CNS (Chinese National Standards), could not be regarded as the true content of organic matter in an organic fertilizer, and that the OXC (heating) value determined using the wet oxidation method was close to the content of total organic carbon in organic fertilizer. Therefore, it is better to use the content of total organic carbon as the standard item for organic fertilizers rather than the assumed content of organic matter determined using the dry ash method.

並列關鍵字

Organic matter content ； Dry ash method ； Wet oxidation method ； Elemental analysis method