Microbial Population Dynamics and Composition in Crude Oil Contaminated Soils Treated with Microorganisms and Guinea Grass (Panicum maximum)

Crude oil pollution can cause alterations in the soil physico- chemical properties and microbial activities, with deleterious effects on soil productivity indices. Studies were conducted on a sandy loam soil contaminated with levels of crude oil, bioremediated with bacteria, fungi and guinea grass. The experiment was a 3 x 4 factorial in completely randomized design (CRD) in the screen house in the University of Port Harcourt. Results showed that all the treatments had significant (p<0.05) effects on microbial population, diversity and total petroleum hydrocarbons (TPHs). Bacteria significantly (p<0.05) reduced TPH within 6 to 8 days. Bacillus Streptococcus, Staphylococcus, Aermonnas and Pseaudomanas spp. were the dominant bacteria found in the soil whereas, Aspergillus, Fusarium, Rhizopus, Blastomycetes and Saccharomyteces species were the dominant fungi isolates. Guinea grass was not effective in bioremediation when the crude oil was above 5% w/w level of contamination. Keywords: Crude oil, bioremediation, bacteria, fungi, soil fertility, petroleum hydrocarbon. DOI: 10.7176/JBAH/9-16-01 Publication date: August 31st 201

Bacteria to Fungi Ratio and Organic Carbon in No-till Ultisols after Applications of Corn Residues and Poultry Manure

No-till system may greatly increase soil organic carbon (SOC), and modify soil structure and water retention properties in the plough layer. Additions of organic materials of contrasting C and N ratio in no-till system require better understanding because they could cause a shift in the bacterial to fungi ratio. We studied the effects of short-term additions of 10 t ha -1 dry corn residues (CNS10) and 10 t ha -1 poultry manure (PM10) on bacteria-fungi ratio and other properties in a no-till ultisols. Results showed that PM10 improved SOC content of soil by 49.7% while CNS10 added 14.2% of SOC to the soil. There were significant (p < 0.05) increases in total N and available P in PM10 soils. Total N ranged from 4.8 g kg -1 in the control to 8.1 g kg -1in PM10, while available P increased by 117% compared with the control. Application of 10 t ha -1 poultry manure caused a major shift in microbial community towards greater bacterial population, whereas, dry corn residues encouraged significant shift towards greater fungi population. Relationships showed highly significant positive correlation between bacteria and clay content (r = 0.714, p = 0.01), and negative correlation with sand. Result also showed that fungal population increased with increasing sand content. These results indicate that addition of 10 t ha -1 of poultry manure in a no-till management leads to significant increases in bacterial population, SOC, total N and available P. This method can therefore be recommended to farmers where reserve C and N as well as increased mineralization are needed

CLAY CONTENT, BULK DENSITY AND CARBON STORAGE RELATIONSHIPS IN MANGROVE AND RAINFOREST SOILS DURING DRY AND WET SEASONS

Evaluation of carbon stock in soil is an essential step in estimating the carbon storage potential of an ecosystem. A field study was carried out on a humid tropical Rainforest and Mangrove soils at the Forestry Unit of the Rivers State University Teaching and Research Farm and the Eagle Island quantify the effects of vegetation and seasons on soil organic carbon, organic carbon stock and other physical to attributes of the soils. Results revealed that seasons and vegetation did no change the soil texture, but influenced other properties of the soils. Bulk density was significantly low (p<0.05) at 0.64 g cm-3 in Mangrove soils in the peak of dry season. Saturated hydraulic conductivity (Ksat) was moderately rapid (20.88 cm h-1) in Rainforest soil, and moderately slow (15.59 cm h-1) in the Mangrove soils. Soil organic carbon (SOC) was significantly higher (p<0-05) in mangrove soils at 53 g kg-1 during the rains, and 16 g kg-1 in Rainforest soils during the same season. Soil organic carbon stock (SOCS) was significantly higher at 65.4 kg m-2 in Rainforest soils (p<0.05), compared to 8.4 kg m-2 in Mangrove soils during the same season. SOCS correlated positively bulk density (BD) (r = 0.679, p<0.05) and clay content (r = 0.892, p<0.01). The model: Y = 0.165+4.068x can be used to predict SOCS and bulk density, also the model Y = -0.246+0.361x can be used to predict the effects of clay content on SOCS in the two soils during the seasons. The Rainforest was found to have the potentials to store carbon in the soil than the Mangrove

GREEN MANURES AND NPK FERTILIZER APPLICATIONS EFFECT ON ORGANIC CARBON POOL, SOIL PHYSICAL PROPERTIES AND CUCUMBER PRODUCTION

Deterioration of soil physical properties and organic matter depletion resulting from continuous cultivation of tropical sandy loam soils, even with the regular applications of inorganic fertilizers is common. To regenerate the soil organic matter and maintain soil structural and hydraulic properties for crop production, the effects of different legumes green manures and NPK chemical fertilizer were evaluated after a 3-year field experiments at the University of Port Harcourt, Teaching and Research Farm (2018 – 2021). Treatments were: 5 tons ha-1Centrocema (Ce5), 5 tons ha-1 Gliricidia (Gl5), 5 tons ha-1Calapogonium (Ca5), NPK 20:10:10 (NPK) and the Control, arranged in a Randomized Complete Block Design (RCBD), in 5 replications. Results showed that three annual applications of  Centrocema, Gliricidia, and Calapogonium  increased  soil organic carbon pool at the 0-30 cm topsoil, and reduced the bulk densities by 8.5%, 4.1%, and 7.0%, respectively, compared to the NPK fertilizer and control. The increased in bulk density in untreated  plots led to decrease in water stable aggregates, low water holding capacity and low yield of cucumber crop. Green manures applications increased soil organic carbon pool, improved topsoil physical properties and cucumber yield, while NPK chemical fertilizer had negative effects on these properties