Tropical Grasslands (1989) Volume 23, 1–7

RESPONSE OF PERENNIAL LEGUMINOUS COVER CROPS IN MALAYSIA TO INOCULATION WITH BRADYRHIZOBIUM

FAIZAH ABDUL WAHAB1, R.A. DATE2, R.J. ROUGHLEY3, A. IKRAM1 and S. CHONG KEWI1

1Rubber Research Institute of Malaysia, Kuala Lumpur, Malaysia.
2CSIRO, Division of Tropical Crops and Pastures, Brisbane, 4067 Australia.
3New South Wales Department of Agriculture, Gosford, 2250 Australia.

Abstract

Pueraria phaseoloides and Calopogonium caeruleum were inoculated with strains M11, M28 and RRIM77 at rates to provide approximately 25 × 102, 31 × 103 and 13.6 × 104 bradyrhizobia/seed and sown at 2 sites in Peninsular Malaysia. The sites were selected to represent land previously sown with cover crops and rubber, a likely competitive site for the inoculum, and land where legumes had not been introduced which was expected to be a less competitive site. The soils at both sites had surprisingly low populations of bradyrhizobia; no plot had > 270/g of soil, P. phaseoloides formed more nodules and had a greater total nodule dry weight than C. caeruleum at both sites. Increasing the inoculum potential approximately 100-fold increased nodule number from 3 to 4 per plant at the early (11 and 26 weeks) harvests but at 60, 76 and 88 weeks very few (< 1/plant) were found on either host plant. The percentage of nodules formed by the inoculant strains at 11 and 26 weeks generally ranged between 30–50% and there were no major effects of site, level of inoculation or sampling times. A small plant growth response of P. phaseoloides to inoculation occurred at 26 weeks at the less competitive site but not at earlier or later harvests.

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