EFFECTS OF DUAL PURPOSE KEROSENE DPK ON THE ECOLOGY OF CULTIVARS (MAIZE AND BEANS) RHIZOSPHERE

ABSTRACT

Spillage and indiscriminate disposal of petroleum products in the soil is becoming a visible problem to the ecosystem. These spills may impact soil fertility, low population dynamics of bacteria, and low crop yield. This study was aimed at determining the effects of Dual Purpose Kerosene (DPK) on the ecology of plant. Soil samples were collected from the dump site (longitude 5° 36’35.4’’E and latitude 6 ° 22’21.3’’N) at depth of 5 cm using a soil Auger. The soil was shared into six (6) Experimental Pots, which include; polluted (50 mg/kg) and unpolluted groups and allowed to acclimatized for one week. The experimental points include, (Pot A; Beans treated, Pot B; Beans untreated, Pot C; maize treated, Pot D; maize untreated and Pot E and F; were the control without planting crops). The total heterotrophic bacteria (THB), total Nitrosomonas (TNS) and Nitrobacter (TNC) counts were enumerated using the standard microbiological methods. Phenotypic characterization was used to identify the bacteria isolates. The cultivars (maize and beans) were planted on the grouped soils to observe the physiological changes. The impact of DPK on earthworms was observed at a varied concentration of Dual Purpose Kerosene (DPK) (50 to 6.25 mg/kg) for one week. Shake flask experiment was used to determine the effect of DPK on nitrifying bacteria. The results of the THBC, TNSC and TNBC ranged from 6.67 to 106.7 x 106 cfu/g, 2.00 to13.33 x 106 cfu/g and 6.33 to 14.00 x 106 cfu/g respectively. The following microorganisms; Bacillus sp., Enterobacter sp. and Escherichia coli were obtained as the dominant heterotrophic bacteria, while Nitrosomonas europaea and Nitrobacter winogradskyi were among the nitrifying bacteria. The polluted soil group recorded no growth of the beans after 2 weeks of observation, while the unpolluted soil grew successfully. Acute toxicity of 50 mg/kg of Dual Purpose Kerosene (DPK) on earthworms showed that after one week there was reduction in weight from 2.518±0.95 to 1.778±0.47 g/kg and length from 21.5±6.31 to 11.2±3.03 cm. The results of the effect of Dual Purpose Kerosene (DPK) on the rhizosphere of the plant (polluted maize and beans) showed no morphological reading, as the plant could not survive the toxicity after two weeks of exposure. The EC50 value of Dual Purpose Kerosene (DPK) on the weight of earthworms revealed that at low concentration of 0.85 mg/kg, the maximal effective concentration on the earthworm was 19.63 mol/l while the toxicity response of earthworm was 95%. The shake flask degradation of nitrifying bacteria exposed to Dual Purpose Kerosene (DPK) showed double exponential phase and growth activity from Day 1 – Day 15. The molecular identification and PCR detection of nitrifying bacteria confirmed the identity of the nitrifying bacterial isolates to be Nitrosomonas europae (1), Nitrosomonas europae (2) and Nitrobacter winogradskyi, with a percentage identity of 100, 80.25 and 100 respectively. Hence, this study has shown that Dual Purpose Kerosene (DPK) has serious deleterious effects on the soil microbial activity of Nitrosomonas and Nitrobacter sp. along with other biological sentinels (earthworms) and on the ecology of maize and beans cultivarss.