Assessment of soil quality after constructing a closure dam on a river

Abstract

BACKGROUND AND OBJECTIVE: Reducing the salinity intrusion from sea water, a closure dam has been constructed on Little Feni River at Musapur Union in 2016. The objective of this research was to assess the soil quality based on the variables, i.e., PH, total organic carbon, total organic matter, total nitrogen, phosphorous, potassium, electrical conductivity, salinity and total dissolved solids, respectively.METHODS: A total of 21 soil samples were collected from 7 sampling stations with 10-15cm depth. The PH, total organic carbon, total organic matter, total nitrogen, phosphorous, potassium, electrical conductivity, salinity and total dissolved solids were measured with pH meter, titration, Van Bemmelen factor, spectrophotometer, conductivity meter and salinity meter, respectively. Data were analyzed by statistical package for the social sciences, maps were produced by Arc GIS software and cluster analysis was done by Ward method, respectively.FINDINGS: The mean concentrations of PH, total organic carbon, total organic matter, total nitrogen, phosphorous, potassium, electrical conductivity, salinity and total dissolved solids were 8.1±0.169, 0.506±0.278%, 0.873±0.465%, 0.044±0.023%, 21.599±8.312ppm, 0.462±0.47ppm, 2.024±526.76dS/m, 2.024±2.382ppt and 222.448±259.927ppm, respectively. The study result revealed that the ranges of these soil parameters were 7.19-8.5, 0.27-1.07%, 0.50-1.82%, 0.02-0.09%, 9.45-32.19ppm, 0.25-1.53ppm, 123.23-1625dS/m, 0.64-7.37ppt and 63.57-802.33ppm, respectively. Strong positive correlation observed between total organic matter and total organic carbon (r=0.999), total nitrogen and total organic matter (r=0.998), potassium and electrical conductivity (r=0.991), salinity and potassium (r=0.994), potassium and total dissolved solids (r=0.989). Likewise, phosphorous was positively correlated with potassium (r=0.444), electrical conductivity (r=0.476) and salinity (r=0.467) with significance level of p ≤ 0.05. The variance test elicited that F value of PH, total organic carbon, total organic matter, total nitrogen, phosphorous, potassium, electrical conductivity, salinity and total dissolved solids were 25.505 (p<0.000), 18.011 (p<0.001), 14.013 (p<0.003), 23.478 (p<0.000), 29.393 (p<0.000), 17.924 (p<0.001), 9.502 (p<0.009) and 4.944 (p<0.046), respectively. The spatial distribution showed the reducing pattern of concentrations from outside to inside area of the closure dam. The cluster analysis showed the same sources of origin for pH, total organic carbon, total organic matter, total nitrogen, potassium, phosphorous and salinity (NaCl) which might be the possible cause of anthropogenic activities, i.e., use of chemical pesticide/fertilizer for agricultural cultivable land.CONCLUSION: It is concluded that inside soil was more fertile rather than outside soil after the construction of closure dam. Lastly, the rate of crop production will be increased and soil should be more productive in the study area.