Isolation and Characterisation of Particulate Organic Matter in Some Soils of Ganges Meander Floodplain and Ganges Tidal Floodplain of Bangladesh

The research was conducted with six representative soil series of Ganges Meander Floodplain and Ganges Tidal Floodplain of Bangladesh during the period of September, 2016 to March, 2017 to isolate and characterise the active fraction of particulate organic matter and its effect on nitrogen and other soil properties. A total 36 soils samples (0-15 cm) were collected in the field through random sampling from six representative soil series of GMF and GTF under different cropping pattern. The laboratory investigation was carried out in the Department of Soil, Water and Environment Discipline, Khulna University, Khulna, Bangladesh. The results indicate that the pH of the studied soils was neutral to mildly alkaline and all the studied soils were non-saline. The active fraction of soil organic matter as well as particulate organic matter was found highest (11.62 g/kg) in Barisal and lowest (2.90 g/kg) in Sara soil series. The highest amount of total nitrogen was found in the soil of Barisal (10.88 g/kg) series and the lowest was in Ishurdi (7.02 g/kg) soil series. In the present study, a positive relationship was found between total nitrogen content and particulate organic matter. The highest amount of micro-aggregate associated carbon at > 0.50 mm range was found in the soil of Barisal series (11.26 g/kg) and the lowest was in Sara series (2.11 g/kg). The highest amount of micro-aggregate associated carbon in the range of 0.50-0.25 mm was found in Amjhupi series (10.88 g/kg) and the lowest was in Ishurdi series (7.02 g/kg). Total nitrogen content of the soils was positively correlated with POM, SOM, clay, pH but negatively correlated with silt. Moreover, silt and the particulate organic matter is negatively correlated. Soil organic carbon associated with the aggregates of 0.50-0.25 mm size range had a positive correlation with SOM associated with the aggregates of > 0.50 mm size range which is significant at 5% level. The P value between SOC 2 and SOM is significant, while in case of POM it is highly significant at 5% level of significance.