Symbiotic N2-fixation of Pueraria phaseoloides as influenced by arbuscular mycorrhizal fungi and applied phosphate

Ahmad Ikram A. J., . and M. N. Sudin, . and Jensen E. S., . Symbiotic N2-fixation of Pueraria phaseoloides as influenced by arbuscular mycorrhizal fungi and applied phosphate. pp. 258-269. ISSN 0127-7065

The growth and symbiotic N2-fixation of the plantation legume Pueraria phaseoloides was studied in two P-deficient soils with or without arbuscular mycorrhizas (AM) and applied phosphate. Symbiotic N2-fixation was determined by the 15N-isotope dilution technique. The soils were a heavy-clay Segamat and sandy Rasau series. In both soils inoculation with AM fungi or adding phosphate increased shoot growth and N contents significantly despite contamination from indigenous endophytes in the uninoculated pots. Estimates of the amount of N2-fixed (Ndfa) by P. phaseoloides depended upon the N uptake profiles of the reference plants (Ipomoea batatas and Axonopus compressus) used for the calculations. Symbiotic N2-fixation was lower in the heavy clay than in the sandy soil. Inoculation with AM-fungi or phosphate supply did not affect the uptake of labelled N (Ndff) or Ndfa in the clay soil whereas both treatments significantly improved Ndff and Ndfa of P. phaseoloides grown in the sandy soil. Irrespective of AM fungi inoculation or phosphate supply Ndfa ranged from -6 to 17 in the clay soil and from 10-16 in the sandy soil. Thus more than 80 of the shoot biomass N was derived from soil and fertiliser. The isotope dilution technique allows determination of N in a crop derived from all sources i.e. from fixation soils and fertilisers but is subjected to error problems in methodology related to choice of non-fixing reference crops. A declining soil 15N enrichment and a mismatch in the N uptake patterns between the legume and its reference crop may result in erroneous estimates.

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Abstract

The growth and symbiotic N2-fixation of the plantation legume Pueraria phaseoloides was studied in two P-deficient soils with or without arbuscular mycorrhizas (AM) and applied phosphate. Symbiotic N2-fixation was determined by the 15N-isotope dilution technique. The soils were a heavy-clay Segamat and sandy Rasau series. In both soils inoculation with AM fungi or adding phosphate increased shoot growth and N contents significantly despite contamination from indigenous endophytes in the uninoculated pots. Estimates of the amount of N2-fixed (Ndfa) by P. phaseoloides depended upon the N uptake profiles of the reference plants (Ipomoea batatas and Axonopus compressus) used for the calculations. Symbiotic N2-fixation was lower in the heavy clay than in the sandy soil. Inoculation with AM-fungi or phosphate supply did not affect the uptake of labelled N (Ndff) or Ndfa in the clay soil whereas both treatments significantly improved Ndff and Ndfa of P. phaseoloides grown in the sandy soil. Irrespective of AM fungi inoculation or phosphate supply Ndfa ranged from -6 to 17 in the clay soil and from 10-16 in the sandy soil. Thus more than 80 of the shoot biomass N was derived from soil and fertiliser. The isotope dilution technique allows determination of N in a crop derived from all sources i.e. from fixation soils and fertilisers but is subjected to error problems in methodology related to choice of non-fixing reference crops. A declining soil 15N enrichment and a mismatch in the N uptake patterns between the legume and its reference crop may result in erroneous estimates.

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Item Type:	Article
AGROVOC Term:	Pueraria phaseoloides
AGROVOC Term:	Vesicular arbuscular mycorrhizae
AGROVOC Term:	Nitrogen fixation
AGROVOC Term:	Plantations
AGROVOC Term:	Isotope dilution method
AGROVOC Term:	Inoculation
AGROVOC Term:	Phosphates
AGROVOC Term:	Contamination
AGROVOC Term:	Endophytes
AGROVOC Term:	Nutrient uptake
Depositing User:	Ms. Suzila Mohamad Kasim
Last Modified:	24 Apr 2025 06:28
URI:	http://webagris.upm.edu.my/id/eprint/23423

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