CARBON. NITROGEN AND PHOSPHORUS DYNAMICS INDUCED BY LONG-TERM CULTIVATION AND MANAGEMENT

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dc.contributor.authorTHOMAS, GOLADI JUDAH
dc.date.accessioned2014-02-07T09:09:33Z
dc.date.available2014-02-07T09:09:33Z
dc.date.issued1997-09
dc.descriptionA THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL AHMADU BELLO UNIVERSITY, ZARIA, IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE MASTER OF SCIENCE (M.SC) DEGREE IN SOIL SCIENCE Department of Soil Science Faculty of Agriculture Ahmadu Bello University Zaria. Nigeriaen_US
dc.description.abstractSeveral s t u d i e s in the savanna c o n t i n u e to justify the benefits of inorganic f e r t i l i z e r s. Parallel s t u d i e s on the l o n g - t e rm effects of f e r t i l i z e r s on t h e soils a r e scanty. The objective of t h i s study was to determine t h e impact of inorganic f e r t i l i z e r s with or without farmyard manure on carbon (C), n i t r o g e n (N) and p h o s p h o r u s (P) in a savanna alfisol a f t e r 45 y e a r s of continuous cultivation. Soils for t h e s t u d y were fertilized with N;N+P. N+P+K. farmyard manure (FYM) FYM+N. FYM+Pr FYM+NP and FYM+NPK. Continuous cultivation caused significant losses of C.N and P. The N+P or N+P+K f e r t i l i z a t i on could not mitigate t h e s e losses. Losses of N and P o c c u r r e d mainly in organic forms. However, combination of farmyard manure with N+P and N+P+K fertilization maintained C.N and P at par with or g r e a t e r t h a n the n a t i v e site soil. Inorganic f e r t i l i z e r s s t r e s s e d microbial a c t i v i t y , evidenced by the low microbial biomass C.N and P compared to t h e soil under native vegetation and soils fertilized with FYM+N a n d FYM+NPK. The study f u r t h e r examined the dynamics of inorganic P(P,) and organic (P0) pools of the soils using a modified Medley Fractionation. Continuous cultivation without P, fertilization decreased the concentration of P1 and P0pools including residual P fraction. Fertilization with P, or in combination with FYM (P.N+P+K. FYMP+P, FYM+NP a n d FYM+NPK) increased the concentration of labile P1 pools, but decreased the concentration of P0 pools and the residual P fraction. The t e n d e n c y of t h e residual P fraction to decrease along with P0 pools suggested that the residual P fraction was largely P0, consistent with the correlation between residual P fraction and total P0 (r = 0.74**) and with organic carbon (r = 0.47**). Path analysis of the relationships between resin extractable P and the more stable Pt and P0 pools indicated that 85% of the variations in resin-P were explained by hydroxide extractable P, (OH-P1) and HC1-P, which acted as sinks for fertilizer-P. The contribution of residual P fraction to resin-P was indirect via bicarbonate extractable P„ (HC03-Po) and 0H-Po suported by the significant path coefficients between them. Thus, the hypothesis that considers residual P fraction stable and inactive needs to be revised. The study thus concluded that from the perspective of soil quality maintenance and sustainable landuse systems a rational fertilization strategy in the savanna is one that combines inorganic fertilizers with FYM or organic/crop residue management to maintain SOM.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/564
dc.language.isoenen_US
dc.subjectCARBON,en_US
dc.subjectNITROGEN,en_US
dc.subjectPHOSPHORUS,en_US
dc.subjectDYNAMICS,en_US
dc.subjectINDUCED,en_US
dc.subjectLONG-TERM,en_US
dc.subjectCULTIVATION,en_US
dc.subjectMANAGEMENTen_US
dc.titleCARBON. NITROGEN AND PHOSPHORUS DYNAMICS INDUCED BY LONG-TERM CULTIVATION AND MANAGEMENTen_US
dc.typeThesisen_US
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