Abstract

Several studies on the effect of water treatment sludge (WTS) have been conducted on trace metal contents of sorghum hybrid (Sorghum bicolor (L.) Moench) grown on a mountainous Kumsan district in the Republic of Korea. The objective of the present study was for measuring manganese (Mn) content in sorghum hybrid on an appropriate lamp current with an atomic absorption spectrophotometer. Four treatments were used in this experiment namely: a) without fertilizer (control), b)fermented alum sludge (Compost), c) alum sludge+nitrogen, phosphorus, potassium (Alum+NPK), and d) fermented alum sludge+nitrogen, phosphorus, potassium (Compost+NPK). After sorghum's harvest, the Mn content was investigated with a spectrophotometer on the conditions of three lamp currents; 4, 5, and 6 mA. Several ratios between the background and the absorbance values might be a very useful index for deciding the condition of the Mn analysis. The three ratios, (mean of backgrounds)/(standard deviation of absorbances), (standard deviation of backgrounds)/(Standard deviation of absorbances), and (2 x Standard deviation of backgrounds)/(mean of absorbances), were considered to be good tools for appropriate Mn analysis. As a result, 5 mA current was favorable for the analysis, therefore, the Mn content was calculated on 5 mA lamp current. There were significant differences of Mn contents among the four treatments: (Alum+NPK) < control, compost or (compost+NPK). The Mn contents of the sorghum for all the four treatments were higher than 40 mg/kg DM (dry matter), and they were considered over-optimum level for the ruminants' feed.

Key words: Absorbance, alum sludge, atomic absorption spectrophotometer, background, lamp current, manganese, ratio, sorghum hybrid.