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Articles by K. Okonwu
Total Records ( 5 ) for K. Okonwu
  K. Okonwu and S.I. Mensah
  Effects of NPK (15:15:15) fertilizer on some growth indices of pumpkin, Cucurbita moschata (Duch. ex Lam.) Duch. ex Poir. were studied. Eight treatments viz; 0, 200, 250, 300, 350, 400, 450 and 500 kg of NPK fertilizer per hectare (kg ha-1) were used in a Randomized Complete Block Design (RCBD) with four replicates. These treatments were applied once to two week-old seedlings of C. moschata using ring method. The effects of these treatments on Leaf Area (LA), stem diameter (STD) and number of leaves (NL) were monitored weekly while fresh weight and dry weight were determined after 6 weeks. Soil Organic Matter (OM), Organic Carbon (OC), ash content, pH and nutrient (N, P, K, Ca, Na and Mg) levels were also monitored at 0, 2 and 6 weeks. The study showed that NPK fertilizer increased the LA, STD, NL and nutrient (N, P, K, Ca, Na and Mg) contents of the soil. The highest leaf area, stem diameter, fresh weight and dry weight were obtained from NPK treatment at 300 kg ha-1 while 350 kg ha-1 rate gave the highest number of leaves. Two weeks after treatment, the concentrations of N, Ca, Mg, OM and OC content in the soil were highly increased by the 400 kg ha-1 treatment but the 500 kg ha-1 rate gave the highest concentrations of K and Na. The study after six weeks showed that 450 kg ha-1 rate gave the highest concentrations of Ca, Mg and K in the soil whereas 500 kg ha-1 rate gave the highest concentrations of P, Na and ash content. The 350 kg ha-1 gave the highest N, OM and OC content. At p<0.05, there were significant difference among treatments. The use of NPK fertilizer at an application range between 400 and 450 kg NPK ha-1 is therefore recommended for growing of C. moschata and improvement of the soil nutrients level.
  K. Okonwu , S.I. Mensah and S.M. Sam
  Calopogonium mucunoides Desv. was subjected to varying concentrations of crude oil equilibrated with water. Five treatments viz 0, 5, 10, 20 and 30% were used in a Randomized Complete Block Design (RCBD) with three replicates. These treatments were applied once to two weeks old seedlings of C. mucunoides using ring method and the plants were allowed to stand for eight weeks. The effects of these treatments on plant height, leaf area and biomass of C. mucunoides were studied. The total chlorophyll contents were also studied. The study showed that 5% treatment gave the highest value for plant height and biomass content while 10% treatment gave the highest value for leaf area and chlorophyll content when compared to control (0%) respectively. It was observed that as the concentration of the crude oil increases, there were corresponding reduction in the plant height, leaf area, biomass and chlorophyll content. These results implied that C. mucunoides can tolerate to some degree of crude oil contamination and thus can be used for phytoremediation in crude oil contaminated soil.
  S.I. Mensah , K. Okonwu and M. Yabrade
  Effects of crude oil application on the growth of Rhizophora racemosa seedlings were conducted at undisturbed tidal inundated mangrove wetland, beside the Chevron yard along Escravos River in Warri, Delta State. Seedlings of R. racemosa were subjected to four crude oil treatments viz., control (0 mL), moderate (20 mL), chronic (40 mL) and acute (100 mL), in a randomized complete block design with five replicates. Treatments were applied weekly for moderate and chronic treatments while acute treatment was a single dose using ring method. The growth indices assessed after 12 weeks were plant height, stem girth, number of leaves, leaf length, leaf width, biomass and total chlorophyll of R. racemosa in soil containing varying treatments. The results showed that mangrove seedlings, R. racemosa were sensitive to and were negatively impacted by moderate, chronic and acute exogenous application of escravos crude oil when compared with the control. The results showed that the control treatment gave the highest mean value for plant height and stem diameter of seedlings (40.98±1.783, 0.80±0.058), respectively when compared with other treatments. The number of leaf drop, biomass and chlorophyll content showed a similar trend, respectively. There were significant difference among treatments at p<0.05. This study provides insight on the potential risk associated with R. racemosa seedlings development exposed to crude oil contamination. The study recommends that crude oil pollution should be stop or minimized to the barest minimum during oil exploration and extraction in the mangrove environment.
  K. Okonwu and I.G. Ugiomoh
  The study was carried out to determine the tannin content of five economic plants indigenous to Nigeria. These plants belongs to the families Poaceae (Maize), Fabaceae (Cowpea, Groundnut), Euphorbiaceae (Cassava) and Malvaceae (Okra). The study showed that the percentage tannin content of these plants decreased from week one to week four after planting from 5.20-4.80, 5.40-3.50, 10.20-4.00, 6.90-4.30, 6.30-3.70 for Maize, Cowpea, Groundnut, Cassava and Okra, respectively. There was significant difference in the weekly estimation of tannin content (F3,12 = 7.873, p = 0.0036) and between different economic plants examined (F4,12 = 3.908, p = 0.0295) at 95% confidence level. The tannin content of the plants altered the nutrient dynamics of the soil; this was observed in the increased mean values recorded for organic matter, organic carbon and sulphate content of the soil within the pH range of 5.95-6.65 from week one to week four after planting.
  C. Ekeke and K. Okonwu
  Study on the soil fertility status of University of Port Harcourt, Nigeria was carried out with respect to its land use types. The aim was to establish preliminary data for further studies in the area. Four soil samples were collected randomly from eight plots (10x10 m) length; air dried and analysed to assess the fertility status of the soils. The land use and dominant plant species were also noted. The average concentrations of the heavy metals and physico-chemical parameters showed that within the study area Potassium, K (0.94±1.19 mg kg-1), Lead, Pb (0.22±0.21 mg kg-1), Cadmium, Cd (0.11±0.16 mg kg-1), Manganese, Mn (0.54±0.40 mg kg-1), Chromium, Cr (0.22±0.21 mg kg-1), pH (4.58±0.10), Conductivity, (23.94±10.84 μS cm-1), Available Phosphorus PO43¯ (5.78±4.81 mg kg-1), Nitrate, NO3¯ (2.47±0.82 mk kg-1), organic matter, OM (6.46±2.18%) and Nitrogen, N (0.50±0.44%). Soils within the University Park were generally good for agricultural purposes. However, a little variation exists based on land cover and land-use types. The study establishes that the land-use and land cover system support the fertility of the soil and hence support growth of plant community structure which maintains the ecosystem. The data obtained would serve as preliminary information for further studies.
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