Soil Fertility Status under Different Tree Cropping System in a Southwestern Zone of Nigeria

Tree cropping has been known to bring about changes in edaphic component among other components of the ecosystem through their interactions with the soil and soil faunas. Premised on this, this study assessed the effects of sole cropping of teak and intercropping of cocoa and kola on the soil fertility status. The study was carried out using stratified-randomed sampling technique for the study plots in all the sampling sites. Three sampling sites consisting of four (4)-4oo m2 sampling plots each were established in which vegetation and some soil parameters were assessed. Results analysis showed that the synergistic interaction of leaves decomposition of cocoa and kola improved the organic matter content of the soil under the cocoa/kola site. Considerable improvement in soil fertility was enjoyed in the cocoa/kola site due to the large girth sizes and basal area of trees present in the cocoa/kola site while soil under the sole cropping of teak was impoverished. The degradation effects was due to the high rate of nutrient uptake of the teak, organic matter content was high in the forest site (9.12%) and cocoa/kola site (7.34) while the least was in the teak site (3.04%). A very strong correlation existed between organic matter content and some vegetation parameters

Growth Response of Three Leafy Vegetables to the Allelopathic Effect of <i>Vitellaria paradoxa</i>

<p>This study was conducted to evaluate the growth response of three leafy vegetables (<em>Celosia argentea</em>, <em>Amaranthus cruentus </em>and <em>Amaranthus hypochodriacus</em>) to the leaf extract of <em>Vitellaria paradoxa.</em> Forty-five (45) experimental plastic containers were filled with 5 kg of loamy soil each and randomly allocated to the following regimes: control, 20 g, 40 g, 60 g and 80 g of powdered leaves of <em>V. paradoxa</em>, in three (3) replicates for each test crop respectively.<em> </em>It was observed that the response of the three leafy vegetables, grown within different composition of <em>V. paradoxa</em> leaves, are concentration dependent with respect to the studied growth parameters (plant height, leaf number, leaf area, stem girth). This indicated that <em>V. paradoxa </em>has allelopathic potential on the studied vegetables and therefore it could be used for natural weed control.</p

Assessment of metallic pollution status of surface water and aquatic macrophytes of earthen dams in Ilorin, north-central of Nigeria as indicators of environmental health

The functional quality of an aquatic ecosystem is a reflection of the health of the environment. Therefore, the present study evaluates the trace metal contamination (Pb, Cd, Ni and Mn) of water and aquatic macrophytes in Asa, Agba, Unilorin and Sobi (Moro) earthen dams, north-central Nigeria to evaluate the level of anthropogenic impact on the immediate environment. The concentrations of trace metals in samples of water and available macrophytes from the earthen dams were determined by Atomic Absorption Spectrophotometry. Trace metal contamination of surface water in the earthen dams was assessed using metal index (MPI) and metal pollution index (HPI). The biological accumulation factor of trace metals in the aquatic macrophytes was extrapolated from trace metal concentrations in the water and macrophyte samples. The results of the MPI revealed gross metal contamination of the surface water by Pb and Cd (>6.0 for both metals) in the four earthen dams; while Agba and Sobi dams were slightly contaminated by Ni (MPIs = 1.43 and 1.14 respectively). All the earthen dams were considered safe from Mn contamination (MPI  100), but Asa dam (HPI = 2682.4) was the most contaminated. The biological accumulation factor of Mn in the macrophytes indicated Ceratophyllum demersum, Pycreus lanceolatus and Pistia stratiotes as moderate accumulators of Mn, and can be used as bioindicators in monitoring Mn pollution of aquatic ecosystem. The obtained results in this study showed that the earthen dams are polluted by Pb, Cd and Ni which pose human health risks to the inhabitants through drinking water

Growth Response of Three Leafy Vegetables to the Allelopathic Effect of &lt;i&gt;Vitellaria paradoxa&lt;/i&gt;

This study was conducted to evaluate the growth response of three leafy vegetables (Celosia argentea, Amaranthus cruentus and Amaranthus hypochodriacus) to the leaf extract of Vitellaria paradoxa. Forty-five (45) experimental plastic containers were filled with 5 kg of loamy soil each and randomly allocated to the following regimes: control, 20 g, 40 g, 60 g and 80 g of powdered leaves of V. paradoxa, in three (3) replicates for each test crop respectively. It was observed that the response of the three leafy vegetables, grown within different composition of V. paradoxa leaves, are concentration dependent with respect to the studied growth parameters (plant height, leaf number, leaf area, stem girth). This indicated that V. paradoxa has allelopathic potential on the studied vegetables and therefore it could be used for natural weed control

Transfer of metals from crude oil impacted soils to some native wetland species, the Niger-delta, Nigeria: Implications for phytoremediation potentials

In this study, wetland species growing naturally in the surrounding of two crude oil facilities were sampled and screened for their phytoremediation potentials for zinc, lead, nickel, chromium and cadmium in soil. Concentrations of metals in the root and shoot samples of the wetland species alongside the rhizosphere soil were determined. Metal accumulation in wetland species exceeded the permissible limits, but it was still within phytotoxic thresholds except for chromium. The use of a bioconcentration factor and a transfer factor to screen the wetland species for phytoremediation potentials identified six out of the eight studied species as multi-elemental phytostabilizers of metals in soil. In addition, five of the eight wetland species displayed potentials for phytoextraction of metal, though there was no multi-elemental phytoextractor among the wetland species. Paspalum vaginatum, Andropogon tectorum and Kyllinga squamata portend potential abilities to phytoextract nickel. In addition, Setaria longiseta and Pteridium aquilinum also showed strong potential to phytoextract lead and cadmium respectively from soil. This screening assessment is hoped to be useful in the applications of a cost-effective green technology to remediate heavy metals in contaminated soil

Short-term effects of early-season fire on herbaceous composition, dry matter production and soil fertility in Guinea savanna, Nigeria

The ecological impact of fire regimes on plant diversity and soil fertility has become a subject of intense discussion, especially in savannas where recurring incidences are common. This study assessed the short-term effects of early-season fire on herbaceous composition, dry matter yield and soil fertility in the Guinea savanna belt of Nigeria. Data on ground cover, dry matter yield (DMY) in plants and concentrations of C, N, P, K, Ca and Mg in soil were collected from 10 delineated subplots in the burned and unburned zones of four sites after annual wildfire had occurred. Ground cover was significantly higher in the burned zones, increasing progressively from January to April (dry season). Eleven herbaceous species in addition to 2 tree seedlings occurred and represented families of Asteraceae, Cyperaceae, Fabaceae and Poaceae. Digitaria nuda, Brachiaria lata, Daniellia oliveri and Aeschynomene indica were limited to the burnt zones while Cyperus tuberosus, Mariscus alternifolius and Rottboellia cochinchinensis were restricted to the unburned zones. DMY ranged from 0.32 g m-2 (Desmodium tortuosum) to 52.96 g m-2 (Megathyrsus maximus). Average biomass in the burned and unburned sites was 35.86 g m-2 and 28.42 g m-2, respectively. Soil C, N and P concentrations decreased (positive deterioration index - DI), while those of K, Ca and Mg improved (negative DI) in the burned sites. Burning altered the growth (ground cover) and composition of plant species in the short term, and could significantly influence soil nutrient dynamics in the long term, especially with recurring fire events

Potentially toxic metals in irrigation water, soil, and vegetables and their health risks using Monte Carlo models

Food safety has become a serious global concern because of the accumulation of potentially toxic metals (PTMs) in crops cultivated on contaminated agricultural soils. Amongst these toxic elements, arsenic (As), cadmium (Cd), chromium (Cr), and lead (Pb) receive worldwide attention because of their ability to cause deleterious health effects. Thus, an assessment of these toxic metals in the soils, irrigation waters, and the most widely consumed vegetables in Nigeria; Spinach (Amaranthushybridus), and Cabbage (Brassica oleracea) was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The mean concentration (measured in mg kg− 1) of the PTMs in the soils was in the sequence Cr (81.77) > Pb(19.91) > As(13.23) > Cd(3.25), exceeding the WHO recommended values in all cases. This contamination was corroborated by the pollution evaluation indices. The concentrations (measured in mg l− 1) of the PTMs in the irrigation water followed a similar pattern i.e. Cr(1.87) > Pb(1.65) > As(0.85) > Cd(0.20). All the PTMs being studied, were found in the vegetables with Cr (5.37 and 5.88) having the highest concentration, followed by Pb (3.57 and 4.33), and As (1.09 and 1.67), while Cd (0.48 and 1.04) had the lowest concentration (all measured in mg kg− 1) for cabbage and spinach, respectively. The concentration of the toxic metals was higher in spinach than in cabbage, which may be due to the redistribution of the greater proportion of the metals above the ground tissue, caused by the bioavailability of metals in the aqueous phase. Expectedly, the hazard index (HI),and carcinogenic risk values of spinach were higher than that of cabbage. This implies that spinach poses potentially higher health risks. Similarly, the Monte Carlo simulation results reveal that the 5th percentile, 95th percentile, and 50th percentile of the cumulative probability of cancer risks due to the consumption of these vegetables exceeds the acceptable range of 1.00E−6 and 1.00E−4. Thus, the probable risk of a cancerous effect is high, and necessary remedial actions are recommended