Assessment of Heavy Metal Pollution in the Sediments of the River Pra and Its Tributaries

An investigative study was conducted to determine the heavy metal pollution in the sediment in the Pra Basin of Ghana from 27 sampling points during the dry and wet seasons using the geo-accumulation index (Igeo), enrichment factor (EF), and pollution load index (PLI). Sediments were acid digested and analyzed for the following selected metals: arsenic (As), lead (Pb), cadmium (Cd), zinc (Zn), manganese (Mn), total chromium (Cr), nickel (Ni), and iron (Fe) using the dual atomizer and hydride generator atomic absorption spectrophotometer (model ASC-7000 No A309654, Shimadzu, Japan). The metal concentrations (mg kg^?1) in the sediments were as follows: As (0.175)?<?Cd (3.206)?<?Ni (79.927)?<?Zn (118.323)?<?Cr (216.708)?<?Mn (234.742)?<?Pb (335.381)?<?Fe (1354.513) in the dry season and As (0.002)?<?Cd (7.279)?<?Ni (72.663)?<?Zn (35.622)?<?Pb (135.863)?<?Cr (167.604)?<?Mn (183.904)?<?Fe (1138.551) for the wet season. The EF which is an indication of whether metal concentrations are due to anthropogenic activities shows enrichment at all site for the metals Cr, Pb, and Cd in the wet seasons. However, only 4 out of the 27 sites showed Ni enrichment in the wet season. Contrary to the wet season, only Pb and Cr recorded enrichment at all sites during the dry season. Fifteen out of the 27 sites recorded Cd enrichment and 24 out of the 27 sites recorded Ni enriched during the dry season. None of the sites were enriched with Fe, As, Zn, and Mn in either the dry or wet seasons. For both dry and wet seasons, the pollution load index for all the sites except one was at the background levels which is a sign of non-deterioration of the sites studied. In the wet season, the calculated Igeo reveals that the study area is not contaminated with respect to As, Zn, Fe, and Mn; uncontaminated to moderately contaminated with Cd; moderately contaminated with Cr; uncontaminated to moderately to heavily contaminated with Ni; and moderately to heavily contaminated with Pb. The dry season Igeo results reveal non-contamination of the study area with respect to As, Fe, and Mn; uncontaminated to moderately contaminated with Zn; moderately contaminated with Cr; uncontaminated to heavily contaminated with Cd; uncontaminated to extremely contaminated with Ni; and moderately to extremely contaminated with Pb. The high levels of Cd, Pb, and Cr in all the sites are due to unregulated illegal mining activities occurring in and around the study area. It is hoped that this study will prompt the basin management board to improve their management strategies in controlling unregulated illegal mining in the basin sediments.     

Assessing Sources of Information for Urban Mushroom Growers in Accra,Ghana

This study assessed information sources for urban mushroom farmers in Accra, Ghana. One hundred farmers were sampled, and a structured questionnaire was administered to solicit information from the respondents. Results showed that the majority of farmers were male (71%) and most (60%) with university education. The majority (44%) had 1–5 years of experience in mushroom cultivation. Co-farmers (89.8%), the Mushroom Growers Association (79.6%), training workshops (73.5%), and the Farmers' Forum (29.6%) readily served as information sources for farmers. The research revealed that, for 52% of farmers, ignorance of information sources was a major hindrance in their quest for information.     

First record of Quadrastichus mendeli,a parasitoid of Leptocybe invasa,in South Africa

Leptocybe invasa, the blue gum chalcid, is a well-known pest of Eucalyptus globally. Since it was first observed in the Mediterranean and Middle East in 2000, it has spread to other countries where Eucalyptus have been planted. Efforts to control it have included the release of a number of larval and pupal parasitoids. This report serves as the first record of the presence of Quadrastichus mendeli in South Africa, a parasitoid originally released as a biological control agent of L. invasa in Israel. The interactions and potential impacts on the other insects in the L. invasa galls will need to be investigated.     

Land Suitability Assessment and Landuse Planning： A Prerequisite for Food Security and Climate Change Adaptation

Though Ghana＇s crop yield growth rate was at 17%, 5% of every 1.2 million Ghanaians have insufficient and limited access to nutritious food. Climate change and climate variability have enormously affected the state of agricultural productivity and hence could result in food insecurity. As many ongoing projects use Boolean suitability analysis, land use planning, management recommendations sores, it still remains inadequate to support rural resource poor farmers. This then, is affecting livelihood and agricultural productivity. In this paper, a geostatistical quantitative method to support a geographic information system （GIS） based on multi-criteria decision support system （GMCDSS） for an enhanced land suitability assessment （LSA） and landuse planning （LP） was devised. Project findings indicated that, recommended farm inputs could be estimated and applied accordingly at farm plot levels Soil amendment indicators （e.g., 1.0 t/ha lime ＋ 1.0 t/ha gypsum was estimated for liming） was quantified and currently, farmers can save money in soil fertility management. It has shown that, instead of applying 5.0 t/ha poultry manure （PM） or five bags of N-P-K fertilizer （rate of 15： 15： 15 N-P2O5-K2O/ha） ＋ two bags of sulphate of ammonia （SA）, a farmer may apply 2.0 t/ha PM ＋ two bags 15：15：15 N-P2O5-K2O/ha ＋ one bag of SA. GMCDSS assessment has proved to be fundamental in： （1） urban planning; （2） ensuring food security; （3） poverty reduction and interventions to the effects of climate change and climate variability.     

Weed management on Vertisols for small-scale farmers in Ghana

Vertisols and vertic clays represent a vast crop production resource (300 million hectares world-wide) that is underutilized, mainly because of problems with soil physical characteristics (particularly relating to water) and weeds. These montmorillonitic clays are generally more fertile and have higher water-holding capacities than many tropical soils, but they are difficult to manage as they are very sticky when wet and hard and cloddy when dry. Research in Ghana has shown that it is technically possible to increase crop yields by 90% in normal wet seasons by using raised (camber) beds to control water, but further increases in yield potential are prevented by highpopulations of Cyperus rotundus L. and Imperata cylindrica (L.) Raeuschel. These challenges have been addressed by research on farms and on a research station to determine the effectiveness of glyphosate and camber beds for weed and water management and crop production in maize-based farming systems. Field trials have shown that tuber populations of C. rotundus could be reduced by 95% after glyphosate at 1.8 kg a.e. ha-1 was applied at the beginning of four cropping seasons during 1997 and 1998. The combination of glyphosate for weed control and camber beds to shed excess water produced maize grain yields of 3.5 t ha-1 - a significant increase over the typical yields of ～1.0 t ha-1 withtraditional methods ofhoe-weeding onflat land. Economic evaluations have shown that the returns to small-scale farmers could be considerably increased by the use of glyphosate for weed control.     

Effect of CO2 enrichment on biomass production,photosynthesis, and sink activity in Soybean cv. Bragg and its supernodulating mutant nts 1007

Soybean (Glycine max L. Merr.) cv. Bragg and its supernodulating mutant nts 1007 were grown in pots containing vermiculite with a N-free nutrient solution in order to examine the effect of elevated CO₂ concentration (100+20 Pa CO₂ ) on biomass production, photosynthesis, and biological nitrogen fixation. The whole plant weight increase in Bragg was higher than in the mutant at a high CO₂ concentration. Apparent photosynthetic activities of the upper leaves in both Bragg and the mutant increased up to 14 d after treatment initiation by the CO₂ enrichment and thereafter decreased to some extent. Both leaf area and leaf thickness of Bragg increased more than in nts 1007. With the elevated CO₂ concentration, biological nitrogen fixation (BNF) also responded in the same manner as biomass production in both Bragg and nts 1007. The increase of BNF in Bragg was largely due to an increase in nodule weight. Starch contents in the leaves of both Bragg and the mutant increased significantly by CO₂ enrichment, with a higher increase in Bragg than in its mutant. Sugar content in leaf differed only slightly in both Bragg and the mutant. N content in leaf decreased in both Bragg and its mutant, with the decrease being more pronounced in Bragg. However, in other plant parts (roots, stem, and petiole + pods), N content increased in the mutant while in Bragg, it decreased in the pod. N accumulation rate was higher in Bragg than in the mutant and increased more in Bragg than in the mutant by CO₂ enrichment. The ureide content in leaf decreased in Bragg but increased in the mutant by elevated CO₂ concentration. In the nodules, ureide content increased in both Bragg and the mutant by CO₂ enrichment. Based on these results, it is suggested that in terms of biomass production and photosynthetic rate, Bragg responded more to elevated CO₂ concentration than its mutant nts 1007. The alleviation of the stunted vegetative growth of the mutant by CO₂ enrichment was limited despite the significant increase in the photosynthetic activity, presumably due to the limitation of sink activity in the growing parts and not to insufficient supply of N through BNF.     

Potential of natural and improved fallow using indigenous trees to facilitate cacao replanting in Ghana

Poor establishment, due to loss of soil fertility, weeds and lack of appropriate shade, is a major constraint to replanting cacao on previously used land. Spathodea campanulata, Newbouldia laevis and Ricinodendron heudelotii planted as monospecific improved fallow and Terminalia ivorensis, T. superba and Antiaris toxicaria planted as a multispecies improved fallow and a natural tree fallow were assessed for their potential to facilitate cacao replanting in a randomized complete block design experiment. Simpson and Shannon diversity indices and species richness in the natural tree fallow were 0.6, 1.6 and 20, respectively, at 4 years after trial inception. The Multispecies and the R. heudelotii improved fallows had better height growth, crown development and light transmission characteristics, which are desirable for cacao shade. However, these were not comparable to S. campanulata or the natural tree fallow in terms of improving microsite topsoil pH, % organic carbon and % total nitrogen and site capture. Since optimum fallow period is shortened by growing fast-growing trees, the height growth rate >2.0 m per annum in all the treatments except N. laevis indicates the suitability of these species for improved fallow. The trees species showed different and complementary characteristics and from a standpoint of biodiversity conservation and the future floristic composition of the landscape the natural tree fallow with its diversity of tree species may be recommended as a rehabilitation technique to facilitate the replanting of cacao with a diverse overhead shade.