The Occurrence and Diversity of Indigenous Bradyrhizobia that Nodulate and Fix Nitrogen in Soybean and Pigeonpea in Three Ghanaian Soils Under Different Levels of N And P Fertilizers

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dc.contributor.advisor Danso, S.K.A.
dc.contributor.advisor Owusu-Bennoah, E. Fianko, D. A.
dc.contributor.other University of Ghana, College of Basic and Applied Sciences , School of Agriculture, Department of Soil science 2015-11-23T16:51:03Z 2017-10-13T16:36:49Z 2015-11-23T16:51:03Z 2017-10-13T16:36:49Z 2014-07
dc.description Thesis (MPhil) - university of Ghana, 2014
dc.description.abstract The need to feed the projected world population of 9.7 billion by 2050 has received much attention and increased food production has been recommended to address the problem. Soybean and pigeonpea are important global commercial and food legumes that have been recommended for food security and sustainable agriculture particularly in tropical and sub-tropical regions where the majority of the world’s resource poor live, and where agricultural production is constrained by low soil fertility, primarily by soil N and P deficiencies. It is therefore necessary to enhance the legumes' ability to access more and more of their N from biological nitrogen fixation, so as to decrease the need for expensive inorganic N fertilizers especially for these poor farmers. There is, however, limited information on biological nitrogen fixation and factors that affect this process in Ghana. In this study, the effects of phosphorus and nitrogen on nodulation, dry weight of nodules formed and growth of soybean and pigeonpea were determined. Except at excessive rates of P (160 kg P/ha and 200 kg P/ ha) which decreased nodulation and growth of nodules formed on pigeonpea in the Haplic Acrisol from the coastal savannah, application of P increased nodulation and growth of nodules in both pigeonpea and soybean. In contrast to P, N application to soil inhibited nodulation in the legumes. Application of 80 kg/ha P and above in combination with an inhibitory rate of N (100 kg N/ ha) revived nodulation and nodule growth in all cases. The conclusion from this study is that, for a given legume, the amount of N in a soil's solution that may induce toxicity and subsequently inhibit nodulation under low P conditions would not be enough to support the growth and nodulation of that same legume when P is applied to the soil. Such conditions become favourable for the growth of the legume as well as nodulation in the presence of compatible bradyrhizobia. The effect of the application of P on N acquisition and symbiotic N2 fixation in soybean plants grown in a coastal savannah Haplic Acrisol was also determined in another study. Application of P enhanced both % Ndfa and total N fixed. Highest increase in BNF occurred between the 0 and 40 kg P/ ha. However, highest % Ndfa (54.7 %) and total N2 fixed (51.5 kg N/ha) occurred when 120 kg P/ ha was applied to the soil. The conclusion from the study is that nodules were more efficient at fixing N at lower P rates compared to higher P rates. In this study, the indigenous populations of bradyrhizobia for cowpea and soybean were estimated using the most probable number (MPN) plant infection assay. Except for the Ferric Acrisol which contained very low populations (less than 10 cells/ g soil) of indigenous soybean Bradyrhizobium, the Haplic Acrisols from the coastal savannah and semi-deciduous forest both contained satisfactory number of indigenous bradyrhizobia that were capable of nodulating both Soybean and Cowpea. The diversity of 120 bradyrhizobial strains isolated from cowpea, soybean and pigeonpea root nodules was investigated using DAPD and RAPD fingerprinting with primers RPO1 and RPO4, respectively. Based on the combined RPO1-PCR and RPO4-PCR patterns, a high diversity existed within and between indigenous bradyrhizobial isolates that nodulated cowpea, pigeonpea and soybean grown in the soils from the different agro-ecological zones. Phosphorus application had varying effects on the diversity of isolates from the different soils that nodulated soybean pigeonpea and cowpea. The conclusion is that, the increased number of nodules formed on legumes with P application is not always associated with increased diversity of the compatible bradyrhizobia. Thus bradyrhizobia differ in their soil P tolerance. en_US
dc.format.extent xvi, 192p. ill
dc.language.iso en en_US
dc.publisher University of Ghana en_US
dc.title The Occurrence and Diversity of Indigenous Bradyrhizobia that Nodulate and Fix Nitrogen in Soybean and Pigeonpea in Three Ghanaian Soils Under Different Levels of N And P Fertilizers en_US
dc.type Thesis en_US
dc.rights.holder University of Ghana

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