Impact of Nitrogen Fertilizer Use on Soil Ecosystem Integrity in the Greater Port Harcourt Region, Nigeria

Abstract

Fertilizers are used to increase crop yields in agriculture but can affect the integrity of soil ecosystems if misused. The present study was conducted to observe the impact of inorganic fertilizers in selected soils in Greater Port Harcourt Area on soil microbial population, in addition, the association between soil microbial population and Lethal Concentration 50 (LC₅₀) was observed. Microbial communities and LC₅₀ values were determined using normal analytical procedures. The study showed various fertilizer types that altered soil microbial population and LC₅₀ values. For agricultural areas the maximum NPKB mean value was 0.70±0.76 ppm which was higher than the mean value of the control location of 0.23±0.00 ppm. Urea tolerant fungi’s (UREAF's) LC₅₀ mean value was 0.43±0.09 ppm in the agricultural area as compared to the control with a mean value of 0.46±0.00 ppm. Industrial and urban areas had significantly different mean values of 0.29 ± 0.19 ppm and 0.18±0.01 ppm and 0.23 ± 0.06 ppm and 0.23 ± 0.060.17 ± 0.010.17 ± 0.010.17 ± 0.01 ppm respectively (p = 0.001). This research concluded that the application of UREA and NPK fertilizers in study area soils lowered the pH of soils in A1, A2 and A3 agricultural sites. Application of UREA and NPK fertilizers in soils of the study areas increased the population of microorganisms in threshold concentrations but was detrimental for NPK and UREA fertilizers at concentrations of 1.50% or above. Further findings showed that microorganisms were more tolerant of NPK and UREA fertilizers in agricultural areas compared to urban and industrial areas which showed higher LC₅₀ values. This research concludes that fertilizers used in the study areas were related to soil microorganisms developing tolerance to NPK and UREA. Farmers should observe application of the recommended professional quantities of fertilizers to ensure the sustenance of the soil ecosystem integrity.