Population and effectiveness of N2 fixation of indigenous groundnut rhizobia sampled from different cropping systems
1993
Preecha Wadisirisuk | Achara Nantakit | Somsak Kotepong | Nantakorn Boonkerd (Department of Agriculture, Bangkok (Thailand). Soil Science Div. Soil Microbiology Research Group)
Population and effectiveness of indigenous groundnut rhizobia are the most important factors affecting the response of groundnut to rhizobial inoculation. This experiment was conducted by collecting 55 soil samples from lands of different cropping patterns in all regions of Thailand for enumeration and isolation of groundnut rhizobia. Results showed that cropping systems had a great influence on the number of indigenous population. Number of indigenous rhizobia was greater in the land continuously grown to groundnut or grown to other crops in rotation with groundnut or mungbean than those numbers of soils sampled from grass land or woodland. Soils sampled from lands continuously grown to non-leguminous crops such as corn, sugarcane, cassava, pineapple and woodland where leguminous plants were not found, contained only a small number of rhizobia. Thus, rhizobial inoculation should be recommended if groundnut has to be grown in these last mentioned areas. Test of 500 groundnut rhizobial isolates from those collected soils showed that most of them could fix N2 as effectively as or better than the standard strains. Results of this experiment can be concluded that there is no need to inoculate groundnut seed at planting if it is grown in the land where groundnut has been grown continuously for a long time.
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