EVALUATING NUTRIENT ELEMENTS AND HEAVY METALS IN FRESH AND COMPOSTED MANURE OF DIFFERENT LIVESTOCK

摘要

Application of livestock compost as a fertilizer helps to provide essential nutrients (K, Ca and Mg) to the plant but it can contaminate the environment with heavy metals; therefore, the heavy metal contents of manure must be exactly determined. This study aims to compare the elements (K, Ca, Mg and heavy metals) in fresh versus composted animal manure. Composted and fresh animal manure from four different sources, including buffalo (BF), cow (CW), goat (GT) and poultry (PL), were selected to determine K, Ca, Mg, Fe, Zn, Ni, Mn and Hg by atomic absorption spectrophotometry. The extractability of elements varied considerably depending on the type of livestock and extraction method. During the extraction, concentration of elements varied as follows: Mg＞ Ca＞K. Mg and Ca were highest in both composted and fresh animal manure whereas significantly decreased K was observed in both manure types. The water-soluble heavy metals varied in the order of Hg＞Ni＞Mn＞Zn＞Fe. The composted and fresh manure exhibited lower concentrations of water-soluble heavy metals compared to other elements. Fe, Ni and Mn were found to be higher in composted manure whereas Zn and Hg showed their maximum concentrations in fresh manure. The greater concentrations of all elements were found in BF compost and CW fresh manure while the minimum was observed in PL compost and BF fresh manure, respectively. Analytical results indicate that composting of animal manure encourages soil micro-bial activity, which promotes the soil's trace mineral supply, improving plant nutrition.