The study was conducted to explore the seasonal changes of soil salinity and nutrients in three selected upazilas of Bhola district throughout the year 2019. Soil samples were collected randomly from the agricultural land covering the seasons of dry (November to May) and wet (June to October), respectively. The soil properties (salinity and nutrients) were analyzed in the laboratory of the Department of Environmental Science and Resource Management, Mawlana Bhashani Science and Technology University, Tangail. Study revealed that pH and Exchangeable Potassium (EK) changed significantly among the upazilas. The soil pH was found 6.35, 6.47 and 6.88 in Bhola sadar, Daulatkhan and Manpura upazila, respectively. The EK content was measured as 0.18, 0.16 and 0.30 meq/100g for Bhola sadar, Daulatkhan and Manpura upazila, respectively. The soil pH varied significantly between dry and wet season. The soil pH was found 6.35 in dry season indicated slightly acidic, whereas soil pH (6.79) of wet season indicated neutral in status. The soil EC varied significantly between dry and wet season. These EC values confirmed no excessive salinity in the studied soil of Bhola Island. In the study, the total organic matter (TOM), total nitrogen (TN), available phosphorus (AP), available sulphur (AS) and exchangeable magnesium (EMg) were not varied significantly among the studied upazilas. The study also revealed that in dry season, soil EC was positively correlated (not significant) with AS and EK, whereas negatively correlated (not significant) with TOM, TN, AP and EMg. During wet season, EC was positively (significant, r=0.722, p≤0.05) correlated only with EMg. The study recommended that the constructing and repairing of coastal embankment to protect low lying coastal area to river erosion or flooded water washed away soil nutrient’s; cultivating native high yielding variety; using proper fertilizer application; implementing integrated soil nutrient management; and adapting integrated coastal zone management (ICZM) to increase soil fertility level that ultimately leads to rise up crop production in the coastal Bhola island in Bangladesh.
Key words: coastal Island, soil salinity, soil nutrients, seasonal variation.
Bangladesh has a total of 2.85 million hectares of coastal and offshore land areas (711 km long), that consist of a large network of river system draining the vast flow of the Ganges-Brahmaputra-Meghna river basin (Minar et al., 2013). The country has 3 distinct coastal regions as western, central and eastern coastal zones (Ali, 1999) which cover 19 districts located near the Bay of Bengal, comprising about 32% of the country’s total land area (47211 km2). Among them about 0.83 million hectares are arable land (Haque, 2006). The Government of Bangladesh recognized coastal regions an area of enormous potentials for crop production. In contrast, these areas are lagging behind in socioeconomic development, vulnerable to different disasters, environmental degradation, and global climate changing process (Hossain et al., 2015). Global climate change, the major remarkable concerns of recent times is increasing the salinity in coastal region of Bangladesh (Islam, 2004). Climate change induced impact like low rainfall, extreme temperature in dry season, saline water intrusion due to sea level rise and rise up shrimp cultivation are caused of altered soil nutrient status that is eventually impacting coastal agricultural production on a large scale in Bangladesh (Ashman and Puri, 2013). Average soil salinity at the coastal area are higher in the low flow season than the high flow season because of less freshwater flow from the upstream and water logging is another problem that caused of increasing soil salinity in the coastal zone (Awal, 2014). Agro ecologically the country was divided into 30 regions with different soil properties (Islam, 2008). The cropping patterns are most important in the High Ganges River Floodplain Soils (AEZ-11) of Bangladesh (Das et al., 2018).