가축분뇨 액비 중의 총 질소함량이 많고 적음에 관계없이 일정부분 질산태 질소의 형태로 존재하며 특히 질소의 농도가 낮은 저농도 액비의 경우 질산태 질소의 농도에 따라 총 질소 함량이 달라질 수 있다. 이를 개선하기 위한 방법으로 가축분뇨 액비 총 질소의 분석 시 액비의 황산 분해 후에 devarda’s alloy를 첨가하면 액비에 포함되어있는 질산태 질소까지 정량할 수 있기 때문에 총 질소 정량을 효과적으로 할 수 있는 장점이 있다.
Liquid livestock manure (LLM) has been used as a nitrogen fertilizer source for horticulture plants. LLM contains organic nitrogen (N), ammonium, nitrate, and nitrite. The amount of nitrate and nitrite in LLM are usually small compared to the amount of ammonium in it and so they can be negligible if total nitrogen (N) concentration in LLM is higher than 1,000 mg L<SUP>-1</SUP>. However, if total N concentration in LLM is less than 1,000 mg L<SUP>-1</SUP>, the amount of nitrate and nitrite may affect total N concentration in LLM. Currently, Kjeldahl digestion method is mainly used for ammonium-N in LLM. Therefore, it is ineffective to analyze nitrate-N and nitrite-N. The objective of this study was to evaluate whether the total N concentrations are affected by the amount of nitrate-N and nitrite-N with diverse LLMs by Kjeldahl method (with and without Devarda’ alloy after Conc. sulfuric acid digestion). Five liquid livestock manure samples were collected at swine farms in Ansung and Icheon. All LLM samples were stored at 25℃, subsampled at every 15th day for 90 days, and analyzed for total N, ammonium-N, and nitrate-N. At the 90th day, LLM samples were analyzed with and without Devarda’ alloy after Conc. sulfuric acid digestion. Potassium nitrate, ammonium nitrate, and ammonium chloride were used to determine the N recovery percentages. Total N concentration ranged from 560 to 4,230 mg L<SUP>-1</SUP>. Nitrate-Ns were found in all LLM samples, ranged from 21 to 164 mg L<SUP>-1</SUP>. N recovery percentages with potassium nitrate were 0 % without Devarda’ alloy and 100% with Devarda’ alloy because adding Devarda’ alloy facilitated nitrate-N into ammonium-N conversion. Total Ns were significantly different between two methods, with and without Devarda’ alloy. Total N concentrations were 210 mg L<SUP>-1</SUP> at LLM 4 and 370 mg L<SUP>-1</SUP> at LLM 5 without Devarda’ alloy and 290 mg L<SUP>-1</SUP> at LLM 4 and 490 mg L<SUP>-1</SUP> at LLM 5 with Devarda’ alloy. These results suggest that if total N of LLM is less 1,000 mg L<SUP>-1</SUP>, additional procedure such as adding Devarda’ alloy can be used to estimate the total N and inorganic N better.