Physico-chemical, changes in livestock feces during composting

The properties of livestock manure during composting were studied in order to understand the changes in physical and chemical composition. The composting was carried out in a commercial organic fertilizer plant utilizing aerobic processes, and the following parameters were measured in samples collected at different stages of composting: moisture content, temperature, total carbon (C), humic substance (HS) contents and fractions-fulvic acid (PA) and humic acid (HA), and macro- and micronutrients. Correlation analysis was carried out between these manure properties. Total C and nitrogen (N) decreased by 18 and 10% in the final manure at the end of composting. During composting, HA became progressively the dominant fraction of HS. Phosphorus (P) increased by 31%, potassium (K) by 12%, magnesium (Mg) by 11%, and calcium (Ca) by 6%, respectively. The C/N ratio decreased slightly from an initial value of 14.8 to 12.9 after the composting process. The compost was highest in iron (Fe) and lowest in copper (Cu) content. Highly significant positive correlations were found between total N and HS, implying that HS could be the major determinant of N level in the manure. Significant positive correlations were obtained between zinc (Zn) and HS and FA whereas a highly significant positive correlation was noted for manganese (Mn) and HA. Since the content of N tended to decline during composting, it could be necessary to supplement the manure with inorganic sources of N depending on soil nutrient status and crop requirement.