Pedosphere 6(4): 321--327, 1996
ISSN 1002-0160/CN 32-1315/P
©1996 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Estimation of N2 fixation by some legumes using 15N-labelled soil in greenhouse experiment
WEN Qi-Xiao, CHENG Li-Li, WU Shun-Ling and DU Li-Juan
Institute of Soil Science, Academia Sinica, P. O. Box 821, Nanjing 210008 (China)
      Pot experiments were carried out to estimate Nz fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled soil used was prepared by growing corn-wheat-corn successively on a nearly organic-matter-free Xiashu loess supplemented with adequate amounts of (15NH4)2S04, P, K and micronutrients, then incorporating these 15N-labelled plant materials into the soil after each harvest, and allowing the plant materials to be decomposed aerobically for 410 d after incorporation of the plant material of the third crop. The 15N enrichment of wheat plant-N varied slightly with organa,with a maximum difference of 9.8%. Based on 15N enrichment of soil N inferred from the mean value of the 15N enrichment in different organs of wheat 79%-91% of total N in the tops and 67%-74% of total N in the roots of legumes studied were derived from atmosphere. Estimate by isotope dilution method was in good agreement with that by the conventional difference method provided values obtained by the latter were corrected for seed N, and also with that from the measurement of N accumulated in the tope of the legumes.
Key Words:  isotope dilution method, legumes, N2 fixation, 15N-labelled soil
Citation: Wen, Q. X., Cheng, L. L., Wu, S. L. and Du, L. J. 1996. Estimation of N2 fixation by some legumes using 15N-labelled soil in greenhouse experiment. Pedosphere. 6(4): 321-327.
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