No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Phytoremediation is a relatively new technology that uses plants for the clean up of contaminated soils.Its low cost, simplicity and environmentally friendly approach make this technology a viable option for remediation but the main drawback is that it must be considered as long term alternative given its slow speed. This work is the first to report the use of Plant Growth Regulators(PGR)to enhance the performance of phytoremediation so that less time is needed for remediation.Soil samples were taken from a heavy metal contaminated, abandoned mine site for plant growth trials. A clean soil was also analysed and used for reference.Trials were carried out by growing corn in the contaminated soils and using various concentrations of IBA and NAA together with soil amedments to see if these could increase the accumulation of Zn, Mn, Cu, Bb and Fe in corn. Several further tests were conducted and results noted. / Doctor of Philosophy (PhD)

Abstract In this study, 30 cowpea genotypes were assessed for symbiotic N2 fixation in 2005, and 15 of them were reevaluated in 2006 using the 15N natural abundance technique. Shoot dry matter yield of cowpea genotypes increased significantly in cvs. Vuli-1, Glenda, IT93K-2045- 29, IT90K-59, Omondaw, Apagbaala, and IT84S-2246 in 2005 producing about 3.0 to 3.6-fold more biomass relative to cv. Vallenga. In 2006, seven out of the 15 cowpea genotypes tested (namely, IT97K-499-39, TVu11424, Botswana White, IT84S-2246, Sanzie, Brown Eye, and Glenda) also produced more dry matter than cv. CH14. Shoot δ15N values ranged from −0.58‰ to 1.49‰ in 2005, and −1.51‰ to 1.40‰ in 2006, and these resulted in %Ndfa values of 63.5–86.7% and 56.2–96.3%, respectively. The amount of N-fixed was 49–178 kg N ha−1 in 2005 and 62–198 kg N ha−1 in 2006. Furthermore, there was a direct relationship between the level of symbiotic N nutrition and plant growth, and between grain yield and amount of N-fixed in 2005 and 2006. As a result, genotypes that fixed the most N also produced the largest biomass and the greatest amount of grain yield. The observed relationship between N2 fixation and biomass confirmed our view that cowpea (and other grain legumes) can be concurrently selected for higher N2 fixation, superior plant growth, and greater grain yield. The high levels of N-fixed by many of the cowpea genotypes in this study suggest that they can contribute large amounts of N to cropping systems in African agriculture.