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Field validation of intraspecific variation in phosphorus use efficiency and nitrogen fixation by provenances of Gliricidia sepium grown in low P soils
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Identification of tree species or cultivars/provenances that are tolerant to low levels of available soil P will decrease the dependence on P fertilizer for the good establishment and growth of N2-fixing trees. The effects of phosphorus uptake and use efficiency on N2 fixation and growth of provenances of Gliricidia sepium were determined in the greenhouse and also under field conditions. Three selected provenances out of 23 provenances that had in an earlier experiment been examined at low and high P levels (20 mg and 80 mg P kg−1 soil) were further studied at four levels of P application in the greenhouse at IITA, Ibadan using an Alfisol collected from Fashola. The field experiment was conducted at Fashola (Guinea Savanna Zone), southwestern Nigeria. Large differences in growth occurred among the G. sepium provenances at both low and high P levels. Growth responses of the three provenances to increasing P levels were linear in the pot experiment but variable (linear and quadratic) in the field experiment. Field data show that the growth of one provenance (G1) did not respond to P application while provenance G3 required 80 kg P ha−1 to achieve maximum biomass. Provenance G2 responded to P application up to 40 kg P ha−1 and further addition of P depressed its growth, P uptake and N2 fixation. The results of the pot experiment were not completely duplicated in the field experiments. Differences between G. sepium provenances to P uptake and growth were largely related to differences in physiological P use efficiency and root length, especially at low P, both in the pot and field experiments. In general, nodulation was improved by P application, but varied among provenances. G. sepium fixed approximately 61% and 40% of its N from atmospheric N2 in pot and field, respectively. The percentage of N fixed was affected by the low rate of P application i.e. 20 kg P ha−1 and at high rates of P, no further increase in percentage N2 fixed occurred.
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Permanent link to this itemhttps://hdl.handle.net/20.500.12478/4550
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