Effect of Adding Agricultural and Organic Lime on Soil Properties and Survival Rate of Pathogenic Bacteria (Coliform and E. coli) in Farmland Soils of Kampong Cham Province, Cambodia

Abstract

Cow manure and compost has been applied as fertilizer for many years by farmers in Kampong Cham province. Improperly processed of cow manure and compost may contained pathogenic bacteria such coliform and E. coli that are harmful to humans. Pathogenic bacteria coliform and E. coli are both recognized as hazardous microorganism in the environment and for public health. It is an important pathogen associated with several foodborne and waterborne outbreaks of gastrointestinal illness, which has been widely reported in Cambodia. Also, coliform and E. coli was detected in farmlands soils of Samraong and Baray Communes, Kampong Cham Province. The contamination of agricultural land, surface water, irrigation water, and fresh vegetables, can become a reservoir of infections. Therefore, it is necessary to eliminate the pathogenic bacteria from the contaminated areas. Many studies have shown that inactivation of pathogens in biosolids depends on several factors, from that the soil pH is one of the dominant factors affecting the inactivation of pathogenic bacteria. Increasing of pH can be achieved by adding agricultural limestone calcium carbonate (CaCO₃) or quick lime (CaO). The objectives of this study are to investigate and evaluate the effects of adding different agricultural and organic lime materials on soil chemical properties and the survival rates of pathogenic bacteria coliform and E. coli. Pot experiments was conducted and different CaCO₃ and CaO material such CaCO₃ powder, eggshell, clamshell, and wood ash are used for the soil amendment. The CaCO₃ and CaO added to soil at the ratio of 0 g, 5 g, and 15 g to 750 g of soil to each pot. The CaO obtained by burning the CaCO₃ powder, eggshell, clamshell, and wood ash at 800˚C. Soil chemical and biological parameters such as pH, EC, K⁺, Na⁺, Ca²⁺, coliform and E. coli were determined. The results showed that increase in soil pH due to lime addition were observed. However, there's no significant difference of soil pH responding to amounts of lime added 5 g, 10 g and 15 g. Similar trends were also observed between the unburned and burned lime material. The survival rate of coliform and E. coli were decreased with unburned and burned lime added, the pathogenic bacteria can be eliminated at 7 days after addition of lime. Since the performance of unburned and burned lime on the survival rates of pathogenic bacteria no different. So, it is not necessary to burn the lime material of CaCO₃, eggshell, clamshell, and wood ash. As burning material need the temperature at 800 °C, farmers need a burner machine that can reach to that temperature. Farmers in Cambodia usually burning wood or charco to get the heat. Therefore, it is recommended that farmers can use the unburned lime instead of burned materials in Kampong Cham Province.