Sokoine University of Agriculture

Effects of elevated copper levels on biological nitrogen fixation and occurrence of rhizobia in a Tanzanian coffee-cropped soil

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dc.contributor.author Tindwa, H.
dc.contributor.author Semu, E.
dc.contributor.author Msumali, G. P.
dc.date.accessioned 2016-11-10T11:05:54Z
dc.date.available 2016-11-10T11:05:54Z
dc.date.issued 2014
dc.identifier.uri http://www.suaire.sua.ac.tz/handle/123456789/890
dc.description Journal of Agricultural Science and Applications (J. Agric. Sci. Appl.) en_US
dc.description.abstract A study was conducted to investigate the effects of increasing copper concentration in soil on rhizobial occurrence and the process of biological nitrogen fixation. Two slow-growing bradyrhizobial strains CP, and GM, and two fast-growing rhizobial strains PV, and PV2 were studied by comparing their performance under increasing copper concentrations in greenhouse-based assays involving modified Leonard jar assemblies and potted-soil experiments. Additionally, field samples from soils grown to coffee and subjected to long-term use of copper-based fungicides were analyzed for their total indigenous rhizobial populations using the most probable number-plant infection technique. Results indicated that elevated copper levels in the growth medium had inhibitory effects on nodulation, biological N2 fixation and overall rhizobial numbers in soil. Significant (p= 0.05%) reductions in fresh nodule mass, fresh nodule volume and total shoot nitrogen were recorded when copper concentration was increased from 0 to 100 ppm in both modified Leonard jar assemblies and potted-soil trials. Effective decrements in all the three parameters of fresh nodule mass, fresh nodule volume and total shoot nitrogen were more pronounced with the slow-growing bradyrhizobial strains of CP, and GM, than with the fast-growing PV, and PV2. The MPN-plant infection technique results showed a non-significant (p=0.05) but substantial decrement in rhizobial and bradyrhizobial numbers when the copper-contaminated field soil (82.5 mgCu/g soil) was compared to a control soil (1.8 mgCu/g soil). The study concludes, therefore, that elevated levels of copper in soil could be harmful to free-living rhizobia and their abilities to fix N2 in respective symbiotic associations with legume species. Such negative effects were more pronounced in the slow-growing bradyrhizobial than rhizobial species used. en_US
dc.language.iso en en_US
dc.publisher Sokoine University of Agriculture en_US
dc.subject Biological nitrogen fixation en_US
dc.subject Copper contamination en_US
dc.subject Rhizobia en_US
dc.subject WPN-plant infection technique en_US
dc.subject Tanzania en_US
dc.title Effects of elevated copper levels on biological nitrogen fixation and occurrence of rhizobia in a Tanzanian coffee-cropped soil en_US
dc.type Article en_US


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