Despite the widespread use of Leucaena leucocephala in alley cropping systems, little information is available on the effect of different magagement practices on its nitrogen fixation. We studied the effects of three successive cuttings at 12 week intervals on nodulation and nitrogen fixation of L. leucocephala isolines K636 and K28 inoculated with three Rhizobium strains. The 15N isotope dilution and the total N difference methods were used to estimate the proportions and amounts of N2 fixed. Nodule senescence and decay occurred within 3 weeks after each cutting, new ones being formed to continue N2 fixation during regrowth. At the first and the second cuttings, only K636 responded to inoculation, producing an average of five times more biomass than K28. A response of K28 to inoculation occurred only at the third cutting at 36 weeks after planting. Marked differences also occurred between Rhizobium strains in both N2 fixed and the time course of fixation. With L. leucocephala K636 cut at 24 weeks, plants inoculated with Rhizobium strain IRc 1045 derived 57% of their N from the atmosphere which decreased to 36% at 36 weeks. Opposite results were obtained with Rhizobium strain USD A 3409 on the same isoline during the two periods. No significant differences in % N2 fixed occurred when the three Rhizobium strains were inoculated on K28. Although the average proportion of N derived from the atmospheric N2 fixation remained constant, the total N2 fixed increased significantly with successive cuttings. In K28, there was a good agreement between both methods of estimating N2 fixed, but with K636, the difference method gave a higher estimate of N2 fixed and was less precise.

https://doi.org/10.1007/978-94-009-0585-6_113

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https://doi.org/10.1007/978-94-009-0585-6_113

Soil Fertility; Plant Diseases

Isotope Dilution Method; Leucaena Leucocephala; Nodulation; Nitrogen Fixation; Rhizobium

Acp; Europe

Austria